Style Guide Full Text

    Below is the full text of the Style Guide for Web pages for the Office of Energy Efficiency and Renewable Energy. The guide features formatting, spelling, punctuation, capitalization, grammar, and language guidelines.

    Guidelines are listed alphabetically for easy reference. You may also use the topic index to locate information covered in the guide.

    A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

    a and an

    Use "a" before any acronym or word that begins with a consonant sound. Use "an" before any acronym or word that begins with a vowel sound. An acronym is pronounced as a word (for example, a HEPA filter); an initialism is pronounced as its letters (for example, an NGO). The first sound of the word or letters indicates whether to use "a" or "an."

    Examples:

    • a light-water reactor: an LWR
    • a Human Resources Office memo: an HRO memo
    • a nongovernmental organization: an NGO

    abbreviations

    To avoid confusion, spell out an abbreviation in full or define it the first time you use it in the main body of the text. Spell out a technical abbreviation in full in text when you use it without numerals. For example, write "a few centimeters" rather than "a few cm." Otherwise, use the abbreviation consistently.

    In brochures, exhibits, and other products for a wide audience, limit abbreviations. If you use many abbreviations in a report, add a list of definitions, glossary, or nomenclature.

    1. Abbreviating Measurement Units

      Abbreviate units of measurement when they are used with a numeral or numeric value. With a few exceptions (such as %, °, $, and ¢), use a space to separate them from numerals.

      Examples:

      • 900 W/m2
      • 43 cm
      • 60 Hz

      Define measurement units if they might confuse readers. Spell out the term first, and follow that with the abbreviation in parentheses; thereafter, you may use the abbreviation:

      Example:

      • 250 hectares (ha)

      Spell out units of measurement when they're not accompanied by numbers:

      Example:

      • The new film was several nanometers thicker than the previous one.
    2. Abbreviating Names

      When you first use them, spell out the names of professional societies, organizations, processes, technical equipment, and long chemical terms, followed by the abbreviation in parentheses:

      Use a small s (no apostrophe) for plurals of most abbreviations. For plurals of units of measurement, omit the s (e.g., 15 cm, 6 m, 5 million Btu, 75 dB, 40 W).

    3. Abbreviating Report Elements

      You can abbreviate "equation" and "reference" when you use them with numbers, but spell them out at the beginning of a sentence.

      Example:

      • See Eq. 1-1, Eq. 2-7, and Ref. 10.
      • Equation 2-1 shows the relation.

    See also acronyms and units of measurement. When writing or editing a journal article, consult the publisher's or professional society's guidelines for abbreviations, if they are available. For abbreviations of journal titles, please see the Web of Science website.

    academic degrees

    Avoid the use of academic degrees unless it's absolutely necessary to establish credentials. If it's absolutely necessary, use the following abbreviations after a name and set it off with periods: Ph.D., B.A., M.A., and LL.D. Use them only on first reference. Also, use an apostrophe in bachelor's degree, a master's, etc., but there is no possessive in Bachelor of Arts or Master of Science, for example.

    See the Associated Press Stylebook for more guidelines.

    acronyms

    An acronym is an abbreviation or initialism that is pronounced as a word:

    Examples:

    • RAM
    • NASA
    • OPEC
    • NORAD

    Some common acronyms are no longer capitalized:

    Examples:

    • laser
    • radar
    • sonar

    Avoid the use of acronyms unless they are used extensively in a website or document. In short reports, spell out acronyms that are used fewer than five times. In long reports, spell out acronyms that are used fewer than 10 times. If acronyms are used, spell them out on first use, and put the acronym in parentheses after the full name.

    To avoid confusion, try not to use too many acronyms and abbreviations in any sentence or paragraph. Include a glossary or list of acronyms if your publication contains a lot of them.

    active voice and passive voice

    Try to write more active-voice sentences than passive-voice sentences. In other words, the subject of most of your sentences should be the "actor" or "agent" (who did it?) rather than the thing "acted upon."

    • Active voice: We tested the apparatus.
    • Passive voice: The apparatus was tested by us.

    Research shows that active voice helps even highly educated readers absorb information more quickly. Passive voice is no longer considered to be more scholarly or scientific than active voice. Active voice also lends clarity and vigor to technical writing. But sometimes passive voice is appropriate, especially when it's more important to emphasize what was done than who did it. Passive voice can add variety to your writing, too. See also personal pronouns.

    addresses

    Use U.S. Postal Service abbreviations (such as CO for Colorado and DC for District of Columbia) for states in bibliographies, references, and full addresses (those that include streets or post office boxes).

    Examples:

    • P.O. Box 123
    • Denver, CO 80101

    In text, when you refer to a state with a city or by itself (for example, "The state energy office is stepping up solar retrofit activities in Massachusetts."), spell out the name of the state in full, except for the District of Columbia (D.C.). See also states and countries.

    affect and effect

    "Affect" is usually a verb and "effect" is usually a noun.

    • Affect (verb): The new deposition process affected the efficiency of the device.
    • Effect (noun): We measured the effect of the new process on the efficiency of the device.

    These words can be confusing, because "affect" can sometimes be a noun (when it denotes an emotion), and "effect" can be a verb (when it means "to bring about").

    air conditioning

    Air conditioning is two words when used as a noun and hyphenated when used as an adjective.

    Examples:

    • Air conditioning is energy-intensive.
    • The efficiency of the air-conditioning system can be improved.

    American Recovery and Reinvestment Act of 2009

    After spelling out the full name on first reference, you may use "Recovery Act" in subsequent references instead of the acronym "ARRA." But when using "Recovery Act," do not identify it in parentheses after the full name like you would with the acronym.

    ampersands

    Ampersands can be used in left navigation, right navigation, and in a website's top banner. When abbreviating "research and development," "R&D" is acceptable. Do not use & to mean "and" in other situations.

    appendices

    You can include detailed background or technical information in one or more appendices. Large, detailed tables are often placed in an appendix. If you have more than one appendix, title them with letters (Appendix A, B, C, etc.) and name figures and tables so they reflect the title (Figure A-1, Table B-2, etc.). If you have only one appendix, title it "Appendix" rather than "Appendix A."

    assure, ensure, and insure

    "Assure" means to guarantee. "Ensure" means to make certain. "Insure" means to obtain insurance.

    Examples:

    • The manufacturer assured the group the equipment would work properly.
    • Ensure the lid is fitted properly before starting the experiment.
    • The laboratory must insure the new equipment before it can be used.

    author-date citations

    This is the preferred style for EERE reports and papers. Do not use a comma between the author's last name and the year: (Smith 2000). See also references.

    Back to Top | Topic Index

    bandgap

    "Bandgap" is one word.

    baseload

    "Baseload" is one word when used as a noun or adjective.

    because and since

    "Because" indicates a cause-and-effect relationship. "Since" indicates a time relationship.

    Examples:

    • Because the equipment malfunctioned, the experiment failed.
    • Since we began using the new procedures, there have been no more malfunctions.

    bibliography

    A bibliography, which is different from a reference list, is a list of works that are related to your subject or publication but not cited, either by author or by number, in text. Alphabetize works in bibliographies according to the last name of the first author. Some bibliographies are titled "For Further Reading." Compile your in-text citations of literature and other sources in a list of references.

    BOS

    BOS stands for balance of systems (not system).

    British thermal units

    The abbreviation for "British thermal unit" is Btu. Btu is used for both singular and plural cases.

    bullets

    Bullets are printed to the left of items in a list. You must have at least two items in a bulleted list.

    • Make bulleted lists parallel in construction (that is, begin all the items in the list with the same part of speech, such as a verb or a noun).
      • Make sure items are either all phrases or all complete sentences.
      • Punctuate all items consistently.
    • Use bulleted lists sparingly, in most cases, to highlight important items, draw attention to main points, or help readers find information.
    • Use numbered or lettered lists instead of bullets if you want to refer to items in a list or procedure elsewhere in the text.
    • Begin each item with a capital letter; omit ending punctuation for all but the last item, unless all items are complete sentences.

    In text, the first level of bullet is indented 0.25 in., and text begins at the 0.5-in. mark. This level is bulleted with a solid dot. Second-level bullets are open dots, and third-level bullets are em dashes. Each subsequent level of bullet is sequentially indented 0.5 in. In lists of items that are more than one line, each bulleted item is followed by a 6-pt. space.

    On the Web

    Except for the indenting and spacing formats for reports, all of the above guidelines apply to the Web. When formatting bullets on the Web, there should be a space between the text above the bullets and the first bullet. To help facilitate scanning, you might also consider a space between each bulleted item when the bulleted text is long.

    Back to Top | Topic Index

    capitalization

    1. Capitalizing Proper Nouns

      Capitalize proper names. These include the names of government programs, official projects, formal groups, organizations, companies, the Internet, titles when they precede a name (use lowercase in titles that follow the name), specific geographic areas or features, and ethnic groups.

      Examples:

      • the U.S. Bureau of Mines
      • Solarex Corporation
      • World Wide Web (the Web), the Internet
      • President Carter
      • Christine Johnson, president and chief executive officer
      • the Southwest
      • Lake Powell
      • the Colorado River
      • African, Asian, Caucasian, Hispanic, or Native Americans

      One exception to this rule is companies and products with stylized lowercase or "camel cap" names. In these cases, use the company’s or product’s preferred capitalization.

    2. Capitalizing Taxonomic Names

      When writing about botanical and zoological divisions, capitalize the names of all divisions higher than species: genera, families, orders, classes, and phyla. Print genera, species, and varieties in italics.

      Examples:

      • Clostridium thermocellum
      • Escherichia coli

      After you first mention them (and spell them out), you can abbreviate most generic names followed by species names.

      Examples:

      • C. thermocellum
      • E. coli
    3. Capitalizing Table Titles, Headings, and Captions

      Capitalize the main words of table titles and most headings and subheadings, including the second word in a hyphenated term (e.g., PV Program Five-Year Plan). Do not capitalize articles (e.g., "a," "an," and "the") unless they begin the title or heading; conjunctions (e.g., "and," "or," "nor," and "but"); or prepositions (e.g., "for," "of," and "to") unless they contain four or more letters. When "to" is used in a table title or heading, it is capitalized as an infinitive and lowercase as a preposition. Verbs, including "is" and "are," are always capitalized.

      Examples:

      • Table 1. Number and Frequency of Defects in Six Samples
      • (May–June 1998)
      • Testing the 7.6-m Blades (subhead)
      • Results for E. coli (subhead)
      • Development of Method To Detect Anomalies (subhead)

      Capitalize only the first word and proper nouns in figure captions.

      Example:

      • Figure 1. Results for the electrochromic window

      Follow the style recommended by your professional society or journal publisher regarding the word "figure" and its abbreviation ("Fig.") when you prepare a paper or an article for submission to a conference or journal. Many societies and publishers recommend lowercasing everything but the first word and proper nouns in all table titles, subheads, and captions.

    4. Capitalizing States and Titles

      Capitalize the names of states, but capitalize "state" only when it appears with the entire official name:

      Examples:

      • the State of Colorado; Washington State

      Capitalize titles when they precede the person's name. Lowercase titles and names of groups when they follow the name:

      Examples:

      • Chief Operating Officer Mark Wilson
      • Mary Jones, the president of the company
      • John Smith, the chair of the committee
    5. Capitalizing Trade Names

      Capitalize trade or brand names, and include a trademark, copyright, or other symbol only when it's part of the official name. Include the symbol the first time you use the trade name in body text; thereafter, you may omit the symbol:

      Examples:

    Refer to the company's literature or stationery if you're not sure. See also the online database of current trademarks.

    See also captions, fiscal year, geographic regions, states and countries, and tables.

    Back to Top | Topic Index

    captions

    All substantive photos should be accompanied by a caption. Begin figure and photo captions with a capitalized word and use lowercase thereafter, except for proper nouns and capitalized abbreviations. You don't need a period at the end of a caption unless you add a subcaption or the caption is a complete sentence.

    chemical terms

    Do not use a hyphen in most chemical expressions, even when the terms are used as modifiers.

    Examples:

    • carbon dioxide levels
    • hydrogen ion activity

    Use a hyphen after prefixes when that's the standard for certain chemical formulas.

    Examples:

    • L(+)-2, 3-butanediol
    • trans -glycol

    Use a hyphen to indicate mixtures or combinations.

    Example:

    • hexane-benzene

    citations

    See references for guidance on author-date and numbered citations.

    cleantech

    "Cleantech" is spelled as one word. It is not hyphenated, and the "t" is not capitalized. The word "cleantech" is typically used in reference to investments in sustainable technologies, including renewable energy and energy efficiency. Don't use as a shortened form of "clean technology" in other references.

    close-spaced sublimation

    The term is "close-spaced sublimation," not "closed-space sublimation."

    cogeneration

    colons

    Colons formally introduce a list or series, a question, or an amplification. Colons often separate the parts of a ratio.

    Examples:

    • We test three types of collectors: flat plates, evacuated tubes, and parabolic troughs.
    • We added enough water to obtain a 3:1 dilution.

    But commas, not colons, usually follow words such as "that is," "namely," or "such as." You don't need a colon after a verb or preposition that precedes or introduces a list ("includes," "to," "with," "between," etc.). Use a colon when a noun (such as "the following") introduces a list in text.

    commas

    1. When To Use Commas

      Use a comma to separate items in a series, including the next-to-last word in the series:

      Example:

      • We develop solar thermal, wind, biomass, and photovoltaic energy technologies.

      Use a comma to separate the parts of a compound sentence linked by a coordinating conjunction (such as "and," "but," "or," or "nor") when each part has its own subject and verb (unless they're very short):

      Example:

      • I laughed at the unintentional joke, but she frowned.

      Use commas to set off nonessential or nonrestrictive (parenthetical) words, phrases, and clauses from the rest of the sentence. In other words, the commas signal that the information between them is something extra and not essential to the meaning of the sentence

      Example:

      • The subsystem, which takes a day to install, will be delivered in two weeks.

      Use commas to enclose the name of a state when it follows a city and a year when it follows the month and day.

      Examples:

      • The test systems in Gardner, Massachusetts, are performing well.
      • The next test sites will be in Golden, Colorado, and Chapel Hill, North Carolina.
      • On April 11, 1998, the committee members completed five of the six objectives.
    2. When Not To Use Commas

      Do not use a comma to separate compound subjects or compound verbs.

      Examples:

      • Theorists and nonspecialists alike agree on the importance of the discovery. (There is no comma between the two parts of this compound subject.)
      • The researchers rolled out the thin metal sheet and formed it into coils. (There is no comma between the two parts of this compound verb.)

      Do not use commas to set off words or phrases that are restrictive, that is, essential to the meaning of a sentence.

      Examples:

      • Only the sensors that were attached to the outer edge failed. (The words are essential to the meaning of the sentence.)
      • The system will work efficiently only if it includes storage. (The words are essential to the meaning.)

    See also which and that.

    compose and comprise

    "Composed of" is correct; "comprised of" is incorrect.

    Examples:

    • The United States is composed of 50 states.
    • The parts constitute the whole.
    • The whole comprises its parts.
    • The department comprises four groups; each group is composed of five to seven scientists, technicians, and support staff.

    Back to Top | Topic Index

    compound words, unit modifiers, and hyphens

    1. Verb Phrases: Verb, Noun, and Adjective Forms

      Verb phrases that contain an adverb (build up, set up, start up, break down) are usually written as two words. The noun and adjective forms of these words are either one word (no hyphen) or a hyphenated form of the words. However, there are exceptions. Refer to the dictionary for the correct spelling.

      Examples:

      • We observed the slow buildup of biofouling on the blades.
      • We helped with the setup.
      • The start-up costs were higher than we estimated.
      • I think I'm having another breakdown.
    2. Compound Words Containing Prefixes and Suffixes

      You don't need a hyphen between many prefixes and suffixes and the root words, unless the root word is a proper noun:

      multidimensional
      multiyear
      reevaluated
      threefold, hundredfold
      (also 100-fold)

      prescreening
      postdoctoral
      retroactive
      nonspecialist
      subassembly

      These prefixes usually require a hyphen: "ex," "self," and "quasi."

    3. Unit Modifiers With and Without Hyphens

      Use a hyphen to indicate that words have been combined into a unit modifier, which is a descriptive expression composed of two or more words that form one new meaning. For example, in the term "flat-plate collector," "flat-plate" is the unit modifier. Although there is a tendency in modern writing to eliminate hyphens, they help prevent ambiguity and confusion. Here are some examples of unit modifiers that usually include hyphens:

      • low-level radiation
      • last-minute addition
      • fatigue-induced wear
      • five-year plan
      • nine-story building.

      To see how adding the hyphen can prevent confusion, consider these examples:

      • The scientists tested a new defect causing gas.
      • The scientists tested a new defect-causing gas.

      In the first example, the scientists might seem to have been testing a defect; in the second example, it's clear that they have tested a gas.

      You don't need a hyphen in common unit modifiers that are not ambiguous or confusing.

      • high school students
      • solar radiation resource
      • solar thermal electric systems

      Don't use a hyphen when both words of a unit modifier are capitalized.

      • Bronze Age tools
      • Vietnam Era veterans
      • Biofuels Program objectives

      Leave out the hyphens if you rewrite a sentence so the words in the unit modifier come after the noun they describe.

      Examples:

      • We purchased state-of-the-art lab equipment.
      • We purchased lab equipment that reflects the state of the art.
      • They made some last-minute adjustments.
      • They made some adjustments at the last minute.

      Don't use a hyphen with a unit modifier containing an adverb ending in "-ly."

      Examples:

      • frequently missed deadlines
      • heavily skewed results

      When you use numbers in unit modifiers, retain all the necessary hyphens.

      Examples:

      • 2-in.-diameter tubes
      • 13-cm-wide substrate

      Or rewrite the sentence to omit the hyphens.

      Examples:

      • tubes that are 2 in. in diameter
      • a substrate that is 13 cm wide

      Use a hyphen between prefixes and proper nouns (but not common nouns) or dates, whether they're used as nouns or modifiers.

      Examples:

      • non-EERE
      • mid-1990s

      Use two hyphens when adding a prefix to a word that already contains a prefix, even when there is no hyphen after the prefix in the original word.

      Example:

      • non-self-limiting

    comprise and compose

    See compose and comprise.

    Congress and congressional

    Capitalize "U.S. Congress" and "Congress" when referring to the U.S. Senate and House of Representatives. Lowercase "congressional" unless it is part of a proper name.

    Example:

    • The U.S. Congress is reviewing congressional salaries. A full list is available in the Congressional Record.

    cooperative research and development agreement

    On first reference, use lowercase for "cooperative research and development agreement" because it's not a proper noun. On second reference, you can use the acronym "CRADA."

    coproduction

    countries and states

    See States and Countries.

    CPV

    CPV (concentrating photovoltaics) uses lenses to intensify the sunlight striking PV cells, which enhances the cells' electricity production.

    criterion, datum, memorandum, phenomenon, and their plurals

    "Criterion" is a singular noun (one criterion), and "criteria" is the plural (two or more criteria). "Data" is the plural of "datum." The plural of "memorandum" can be either "memoranda" or "memorandums." "Phenomenon" is singular, and "phenomena" is plural.

    CSP

    CSP (concentrating solar power) captures the sun's heat and uses the thermal energy to produce electricity (e.g., via a steam turbine).

    Back to Top | Topic Index

    dashes

    Use dashes (often called "long dashes" or "em dashes") to enclose and set off parenthetical (nonessential but often illustrative) information in a sentence. Also use dashes to set off a list of items separated by commas. Do not add spaces around the dash.

    Example:

    • The polymer components of the cell walls—cellulose, hemicellulose, and lignin—provide the feedstocks for these chemicals.

    Use an em dash to signal that an important point is going to be made or that a change in the construction of the sentence follows.

    Examples:

    • The presentation concluded with a discussion of the two project factors that concern contractors the most—cost and time.

    • The major omission in the project assessment was the delay caused by the circuit failures—everyone knew about it but no one mentioned it to the reviewers.

    You can usually use commas, colons, and semicolons in place of dashes, but dashes add special emphasis.

    Use shorter dashes known as "en dashes" (rather than a hyphen or em dash) to indicate a range or to substitute for the word "to."

    Examples:

    • 25–45 cm2
    • 2–5 runs per hour
    • See sections 3.1–3.6
    • Jan. 16–Feb. 3, 2011

    In date spans, do not use "from" in conjunction with an en dash (e.g., "from Jan. 16–Feb. 3"). The correct form is "from Jan. 16 to Feb. 3" or "Jan. 16–Feb. 3."

    Do not use an en dash (or hyphen) to mean "and"; the word "between" is followed by the word "and" (not "to").

    Example:

    • between 25 and 30

    Back to Top | Topic Index

    data in tables

    Place a zero to the left of the decimal in any number less than 1 in text and tables (e.g., 0.5, 0.039). Align columns of data vertically on the decimals. When the units of measurement for the data are different, alignment is not necessary (but be sure to specify the units).

    dates

    Use common month abbreviations when a full date is provided. Use cardinal numbers for the day.

    Examples:

    • Jan. 1, 2010
    • May 6, 1990

    degree symbol

    Print the degree symbol right next to the symbol for the temperature scale.

    Examples:

    • 36ºC
    • 85ºF

    Repeat the degree symbol in ranges.

    Example:

    • 32º-36ºC

    Express kelvins as K rather than as ºK; leave a space before the K.

    Example:

    • 85 K

    Department of Energy

    See U.S. Department of Energy.

    disclaimer

    DOE requires EERE publications to include a disclaimer. The disclaimer used depends on the type of publication.

    Example:

    • This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

    dish/engine systems

    Use a slash rather than a hyphen.

    dollars

    Express thousands of dollars using a comma.

    Example:

    • $5,000

    Express millions and billions of dollars this way.

    Examples:

    • $3 million
    • $1.2 billion

    In technical reports and papers, use a dollar sign to express costs less than $1.

    Examples:

    • $0.25
    • $0.06 per kilowatt-hour

    Back to Top | Topic Index

    effect and affect

    See affect and effect.

    ellipses

    When you want to leave out part of text material you are quoting, use ellipsis marks (three dots with a space on each side) to indicate the omission.

    Example:

    • A participle is "a word having the characteristics of both verb and adjective ... [that] shows such verbal features as tense and voice. ..."

    If the words before the ellipses form a grammatically correct sentence, put a period at the end of the sentence and follow it by ellipses. In most cases, however, you don't have to use ellipses at the beginning or end of quotes, just within them. When you add a word or words to the quote, to make it clear, enclose the added word or words in brackets to show that it is not part of the original quotation.

    When you quote whole paragraphs but omit text between any two of them, center three asterisks, with spaces between them (* * *), between the paragraphs quoted. See also quotation marks.

    email

    Acceptable in all references for "electronic mail." Use a hyphen with other e- terms: e-book, e-business, e-commerce.

    Example:

    • I sent an email to everyone involved with the project.

    ENERGY STAR

    ENERGY STAR is always in capitals. If the first instance of ENERGY STAR is in the content, use ENERGY STAR®. If the first instance is in a header, use ENERGY STAR without the superscript. In both cases, use ENERGY STAR thereafter. There is no space between the ® and ENERGY STAR.

    enhanced geothermal system

    The preferred term is "enhanced geothermal system" (EGS). It also sometimes referred to as an "engineered geothermal system."

    ensure, insure, and assure

    See assure, ensure, and insure.

    equations

    Make sure that all the terms in your equations are defined and used consistently both in the text and in subsequent equations, figures, and tables.

    Example:

    • The conductive heat flow equation is:
      dQ/dt = AKdT/dx,

      where
      dQ/dt = the time rate of heat transfer
      A = the area of an end contact
      K = the thermal conductivity
      dT/dx = the thermal gradient.

    etc.

    Because it's vague, please use "etc." (et cetera) sparingly. Don't add it to the end of a list beginning with "for example," or the abbreviation "e.g.," because each word in your list is an example of your subject or topic, but "etc." is not, so you don't need it.

    executive summary

    If you include a summary in a report, place it before the contents page. If your report is brief, a summary is not usually necessary. If your report is long, or if you think some readers will want one, you can include an executive summary. Executive summaries of very long reports can be published separately.

    exergy

    Back to Top | Topic Index

    federal

    Use a capital letter with "federal" for corporate or governmental bodies that use the word as part of their formal names.

    Examples:

    • Federal Trade Commission, Federal Communications Commission

    Use lowercase when the word is used to distinguish something from state, county, city, etc. entities.

    Examples:

    • federal government, federal court, federal judge

    figures

    Figures can include line drawings, graphs, charts, diagrams, schematics, flow charts, illustrations, and photographs.

    For print products, use an Arial font and consistent line weight in your figures. Be sure that computer-generated figures are clear and readable so they can be reproduced easily.

    Use 10-pt. Arial bold for captions; capitalize only the first word and proper nouns. Number figures in a simple sequence (e.g., Figure 1, Figure 2). In long reports, papers, or book chapters, you may include section or chapter numbers in the figure numbers (e.g., Figure 1-1, Figure 1-2, Figure 2-1, and so on).

    Make sure the data in your figures correspond to the data in your text and tables. The caption is placed under the illustration (see also captions).

    Line drawing showing how photovoltaic cells make electricity that can be used and stored from sunlight.

    Figure 2-1. Photovoltaic cells use sunlight to provide energy to a home

    first-person pronouns

    See personal pronouns.

    fiscal year

    Spell out "fiscal year" (e.g., Fiscal Year 2006) the first time you use it; after that, you can abbreviate it using two capitals followed by a space before the full year (e.g., FY 2001). FY01 may be used to save space in charts and graphs. On the Web, always spell out "fiscal year."

    footnotes

    You can use footnotes to place \detailed explanatory or supplementary information at the bottom of a page; use in-text references to cite others' works. Use superscript numerals for footnote numbering. You can also place explanations, details, contradictions, and examples in the text rather than in footnotes. Footnote numbers are printed outside commas and periods but inside colons, semicolons, and dashes.

    The experiment took place in April,1 and it was evaluated in May.2
    We discussed these three stages of writing7: prewriting, writing, and revising.

    Mark the footnotes to tables in EERE reports with superscript letters: a, b, c, etc.

    foreword

    The foreword to a book or formal report contains introductory remarks written, and usually signed, by someone other than the author or authors. Brief introductory remarks written by authors are contained in a preface.

    fractions

    Use words instead of numerals for simple fractions in text.

    Examples:

    • a third of the way
    • one-fifth its actual size
    • three-fourths of the participants

    Write out complex fractions with numerals separated by a solidus.

    Examples:

    • 1/64
    • 23/32
    • 5-1/2 days afterward
    • 2-1/2 times greater

    Display complex, built-up fractions by centering them vertically between two parts of a paragraph.

    Example of an equation centered and placed vertically between two parts of a paragraph.

    Place a zero to the left of the decimal in fractions less than 1.

    Examples:

    • 0.125
    • 0.006

    See also equations.

    Back to Top | Topic Index

    geofluid

    geographic information system

    Do not capitalize "geographic information system" unless used as part of a proper noun. It's also "geographic," not "geographical." Our acronym style guidelines apply as well.

    geographic regions

    Capitalize regions of the United States when they appear by themselves.

    Examples:

    • the East, the West, the North, and the South
    • the Southeast, the Northeast, the Southwest, the Pacific Northwest
    • the Midwest, the East Coast, the West Coast, the Gulf Coast

    Don't capitalize words that merely describe general areas in the country or areas of a state.

    Examples:

    • the eastern United States
    • southwestern Nebraska
    • northern New Mexico
    • the midwestern states

    geopressured geothermal resource

    Geothermal Electric Technology Evaluation Model

    glossaries and nomenclatures

    If you use many mathematical or Greek symbols or technical terms in your report or paper, consider defining them in a glossary or nomenclature. Arrange the list alphabetically, and group Greek letters and definitions alphabetically in a separate list. Nomenclatures are usually in the front of a report, before the contents page. Glossaries usually go in the back, before the references.

    ground-source heat pump

    Back to Top | Topic Index

    heat mining

    hybrid electric vehicle

    This phrase contains no hyphens.

    hyphens

    See compound words, unit modifiers, and hyphens.

    Back to Top | Topic Index

    initialisms

    An initialism is similar to an acronym, but it is pronounced by its letters.

    Examples:

    • American Society for Testing and Materials (ASTM)
    • National Fire Protection Association (NFPA)
    • public utility commissions (PUCs)
    • chemical vapor deposition (CVD)
    • compact vacuum insulation (CVI)
    • chlorofluorocarbons (CFCs)

    Use a small s (no apostrophe) for plurals of most initialisms (e.g., PUCs and CFCs, not PUC's or CFC's).

    Avoid the use of initialisms unless they are used extensively in a document. In short reports, spell out initialisms that are used fewer than five times. In long reports, spell out initialisms that are used fewer than 10 times. If initialisms are used, spell them out on first use, and put the initialism in parentheses after the full name.

    To avoid confusion, try not to use too many in any sentence or paragraph. Include a glossary or list of acronyms if your publication contains a lot of them.

    On the Web

    The above guidelines apply to Web content as well. However, if you use an initialism, spell it out or define it the first time you use it on each Web page.

    insure, assure, and ensure

    See assure, ensure, and insure.

    inverters

    Inverters convert direct current to alternating current.

    italics

    1. Using Italics for Emphasis

      Use italics (sparingly) to emphasize a word or phrase or bring attention to it.

      Example:

      • Never operate this equipment when it has a yellow danger tag.

    2. Using Italics for Foreign Words and Phrases

      Italicize such foreign words and phrases as in situ, in vivo, and inter alia; however, if the word or phrase is commonly used in your field, you may omit the italics.

    3. Using Italics for Hyphenated Prefixes

      Italicize hyphenated prefixes (such as cis-, trans-, o-, m-, and p-) to chemical formulas.

      Examples:

      • trans -1, 2-dibenzoylethylene
      • trans -glycol
    4. Using Italics to Cite Published Documents

      Use italics in references, footnotes, and bibliographies for book titles and the names of journals, newspapers, and magazines.

      Examples:

      • Gone with the Wind
      • Applied Physics Letters
      • The Denver Post
      • Science

      But print the titles of journal and magazine articles in regular Roman type within quotation marks.

      Example:

      • "Solar Chimney Theory: Basic Precepts"
    5. Using Italics in Taxonomic Names

      Unless you're discussing a genus in a general way, use italics to refer to specific genera, species, and varieties.

      Examples:

      • Clostridium thermocellum
      • C. thermocellum

    it's and its

    Even though "it's" has an apostrophe, it isn't a possessive pronoun. "It's" is a contraction, a short form of two words, like "isn't." "It's" always means "it is." "Its" is the possessive form of "it." Like "his," "hers," and "ours," the possessive "its" never needs an apostrophe.

    Example:

    • It's a shame that the company lost its biggest investor.

    Back to Top | Topic Index

    Kalina cycle

    kilowatt

    kilowatt-hour

    laboratory and lab

    Only capitalize "laboratory" or "lab" when used with a laboratory's full name. Lowercase in all other references.

    Example:

    • The National Renewable Energy Laboratory is a U.S. Department of Energy national laboratory. The laboratory is known for its research and development in renewable energy and energy efficiency.

    life cycle

    lightbulb

    "Lightbulb" is spelled as one word.

    lists

    You can use bulleted or numbered lists. Here's an example of a numbered list:

    1. Include at least two items in a bulleted or numbered list.
    2. Use numbered lists for procedural steps and for items referred to elsewhere in text (for example, "as described in Step 2").
    3. Use parallel construction in lists; that is, make all the listed items similar. Use sentences or phrases throughout, and begin each item with a verb or a noun consistently.
      1. Use lowercase letters to mark subordinate items in your list.
      2. Make sure you have at least two subordinate items under each main item.
      3. Indent them like this.
    4. Use punctuation in lists when the items are complete sentences; otherwise, place a period after the last item only.

    You can also list a few items or procedures in paragraph format and number them (1) one, (2) two, (3) three, etc. See bullets for more formatting information.

    lithology

    low-e

    Back to Top | Topic Index

    mathematical symbols

    Leave a space on either side of mathematical symbols used as operation signs.

    Examples:

    • Tin - Tamb
    • ºC × 1.8

    The solidus (a/b) or division sign is an exception. Do not leave a space between numerals and the symbols for degrees, dollars (or cents), and percent (32º, $100, 17%). (Leave a space between numerals and symbols of measurement such as cm and Å, however.) Do not leave a space between symbols such as >, <, and the numeral unless they are the operation signs in an equation.

    measurement units

    See units of measurement.

    megawatt

    megawatt-hour

    metric conversions

    For quick online conversions of English units of measurement to metric units, see the Digital Dutch Unit Converter or the Internet French Property Measuring Units Converter Table.

    metric system

    See SI (Metric) System.

    microgrid

    "Microgrid" is spelled as one word.

    microseismic events

    misplaced modifiers

    Modifiers in the wrong place can make a sentence confusing.

    Example:

    • After identifying the correct material, the test procedure took about 5 minutes.

    In this example, it isn't clear who or what identified the correct material. This might be better: After identifying the correct material, we conducted the five-minute test procedure.

    Example:

    • After being lost under a pile of old reports for 5 years, she finally found the manuscript.

    What, or who, was lost—the manuscript, the woman, or the reader? Try to keep modifiers as close as possible to the people and things they describe. Strunk and White, authors of The Elements of Style, say this: "Modifiers should come, if possible, next to the word they modify." This is especially true for sentences containing introductory prepositional phrases or clauses followed by a comma.

    months and years

    Capitalize the months in all uses. When a month is used with a specific date, abbreviate only Jan., Feb., Aug., Sept., Oct., Nov., and Dec. (Jan. 9, 2008). Also abbreviate these months in tables; however, omit the period. Spell out months when used alone or just with the year; and omit commas when the month and year appear together (October 2001).

    multijunction solar cell

    This term is preferred over "tandem solar cell."

    multiplication symbols

    Be as consistent as possible in using multiplication symbols; as appropriate, choose one symbol (× or ·) or omit the symbol and use proximity or parentheses: ab, (ab) (cd), etc.

    Back to Top | Topic Index

    nation

    Always use lowercase for the word "nation" when referring to the United States.

    Example:

    • Our nation is a leader in renewable energy markets.

    nonattainment

    Spell as one word. Don't hyphenate.

    noncondensable gases

    nonrestrictive phrases and clauses

    A nonrestrictive phrase or clause is one that adds information but is not essential to the meaning of the sentence.

    Examples:

    • The principal investigator, who has studied thin films for 10 years, will chair the panel discussion.

    • The passive solar features, which were suggested by EERE staff, reduced the agency's energy bills by 30%.

    Nonrestrictive or nonessential phrases and clauses are enclosed between two commas when the phrase or clause is within a sentence, and they usually begin with the pronoun "which" rather than "that." See also restrictive phrases and clauses and which and that.

    non-SI (English) units of measurement

    Use non-SI (Systeme International d'Unites) or nonmetric units of measurement (English or Imperial units) instead of metric units only when they are the industry standard. Otherwise, state metric units first, followed by English equivalents in parentheses.

    Example:

    • 38.1 m (125 ft)

    noun and adjective strings

    Try not to string too many noun modifiers together in a sentence. An "agency personnel communications interface display" could also be called a "display of the communications of the agency's personnel." Better yet, it could just be called the "staff bulletin board."

    nouns

    To give your writing more flow and vigor, try changing some of the nouns (especially those ending in –tion and –ment) to verbs (e.g., determine, complete, accomplish, achieve, measure, convert, characterize, combine) and other parts of speech. Doing this will move your readers along more quickly and make it easier for them to understand your text. In these examples, we changed some of the nouns in the first sentences to verbs and other parts of speech.

    Examples:

    • Contraction of the tree stems occurred with rapidity.
      The tree stems contracted rapidly.

    • The frequent result of this process is the combination of the molecules.
      This process frequently causes the molecules to combine.

    • The application of fertilizer has the result of stimulation of the yield.
      Applying fertilizer stimulates the yield.

    Which sentences were easiest to read and understand?

    numbers

    1. Units of Measurement and Mathematical Expressions

      Use numerals with units of measurement and time.

      Examples:

      • 2-1/2 hours
      • 4.5 months
      • 36 cm
      • 87 years
      • 6 liters
      • 25 kW

      With units of time, you can spell out numbers less than 10 if you do so consistently (this applies mainly to outreach products rather than technical reports and papers).

      Examples:

      • five-year plan
      • two-hour test
      • three-week turnaround

      Use numerals to imply arithmetical values or manipulation.

      Examples:

      • a factor of 3
      • multiplied by 2
      • a ratio of 4:5
      • values of 1 and 48

      Express measurement errors as: 6 nm ± 0.2 nm.

      Leave a space between the number and the unit of measurement (0.2 nm) and put spaces around the operation sign; when the measurement error appears by itself, omit the space between the sign and the number.

      Example:

      • The measurement error is ±0.2 nm.

    2. Aligning Numbers

      Align numbers that share a common unit of measurement on the decimals in columns of tables. Put a zero before the decimal in numbers smaller than one.

      Examples:

      • 0.8
      • 2.45
      • 187.362

      If all the numbers in a column do not share the same unit of measurement, you may center the numbers in the column and specify the unit of measurement.

    3. Fractions and Decimals

      You can spell out and hyphenate simple fractions (this is preferred in text) or express them, like more complex fractions, in numerals with a solidus.

      Examples:

      • one-fifth or 1/5
      • 1/64 (but not 1/64th)

      Use a hyphen to separate the integral and fractional parts of a mixed number, or convert the fraction to a decimal.

      Examples:

      • 2-1/2 cm in diameter
      • 2.5-cm-diameter solar cell

      For numbers of 1 million or more, use the numeral (and a decimal, if necessary) and the words million, billion, etc.

      Examples:

      • 1.1 million households
      • 3.5 billion people
      • $2.5 million in funding
    4. Precision and Numbers

      Measurement uncertainty analysis calls for precision in measurements to a significant digit to the right of a decimal point, such as two or three digits (hundredths or thousandths). If you're not absolutely sure, check with an expert before changing the number of digits to the right of the decimal, or rounding the numbers. See also standard errors.

    5. Punctuating Numbers

      Use a comma to separate groups of three digits in numbers.

      Examples:

      • 5,182
      • 113,728
      • 2,225,000
    6. Ranges of Numbers

      To show ranges, use an en dash (which is a little shorter than an em or long dash) with no spaces. Alternatively, if you write out a range, make sure you use the word "to" when you use "of" or "from" before the range. To express a range between some number and another number, always use the word "and" (not "to") with the word "between."

      Examples:

      • 15%-25%
      • from 32º to 40ºC
      • 6-12 cm
      • from 66 to 80 V
      • 10-20 m2
      • between 8 and 12 m (not "between 8 to 12 m")
      • $3 million-$4 million

      Note that some symbols, like º and %, are repeated in a range.

    7. Scientific Notation

      Express multiples of SI (metric) units in powers of 10 with the appropriate prefixes and technical abbreviations.

      Examples:

      • mm (millimeters, 10-3 m)
      • MJ (megajoules, 106 J)

      Use standard scientific notation to express very small and very large numbers.

      Examples:

      • 2.5 × 10-3
      • 3.56 × 106

      Avoid using M to mean "thousands" and MM to mean "millions"; use a capital M for "mega," or millions, as in MW for "megawatts."

    8. Spelling out Numbers

      Except with units of measurement and time, spell out numbers less than 10.

      Examples:

      • eight experimental runs
      • three species of yeast

      Spell out all numbers at the beginning of a sentence.

      Examples:

      • Fifteen trials later, the results were the same.
      • Thirty-five participants attended the seminar.

      When a sentence contains one or more numbers greater than nine that are related to a smaller number, use numerals for all of them.

      Examples:

      • The results were the same in 3, 12, and 18 trials.
      • The contractor tested 8 devices in May, 12 in June, and 9 in July.

      Spell out the first of two adjacent numbers unless the first one requires three or more words.

      Examples:

      • ten 5-kW arrays
      • thirty-two 4-cm2 devices
      • 135 16-cm collectors

    See also fractions.

    Back to Top | Topic Index

    over and under

    In cases involving quantity, use "more than" rather than "over" and "fewer than" or "less than" rather than "under."

    Example:

    • More than 500 people attended the conference, about 100 fewer than last year.

    Back to Top | Topic Index

    parallelism

    Use parallel construction in sentences as well as in lists. Express all similar sentence elements (subjects, verbs, verbals, objects) in a similar way.

    Not Parallel Structure:

    • The lever was moved completely forward, going slightly to the right, and then it went backward halfway in order to complete the procedure.
    • We are not only responsible to our chief customer but also the taxpayers.

    Parallel Structure:

    • To complete the procedure, push the lever all the way forward, slide it slightly to the right, and then pull it halfway back.
    • We are responsible not only to our chief customer but also to the taxpayers.

    parentheses

    Use parentheses as appropriate for explanatory material in text and as shown in the examples that follow.

    1. Parentheses in Equations

      In equations, use parentheses, brackets, and braces in this sequence (which may be repeated as needed).

      Example:

      • {[( )]}
    2. Parentheses With Measurements

      Use parentheses around English measurements that follow SI (metric) measurements.

      Example:

      • 3.1 m/s (7 mph)
    3. Parentheses in Citations

      When you use parentheses in text, such as for author-date references or for parenthetical (added) information, place a comma after the parentheses rather than before them.

      Example:

      • In earlier research (Jones 1989), we showed how quantities of lipids could be increased by this method.

    4. Nested Parentheses in Text

      In body copy, use parentheses, brackets, and braces in this sequence, which may be repeated as needed: ([{ }]).

      Example:

      • (The data presented here [originally derived from Mason {1998}] should not be used for location-specific analyses.)

    passive voice and active voice

    See active voice and passive voice.

    percent, %, and percentage

    Use the symbol % with numerals; use the word "percent" when you spell out numbers at the beginning of a sentence. To determine whether "percent" or % is singular or plural, look at the noun following it. If the next noun is a plural, use a plural verb; if it's singular, use a singular verb.

    Examples:

    • The maximum glucose yield was 60%.
    • Six percent of the pipes were rusty.
    • More than 10% of that amount was allocated to planning.

    When there is no number, use the word "percentage," unless people in your field use a different terminology, such as "percent difference."

    Example:

    • This table shows the percentages of government buildings having solar roofs, by state.

    periods

    Periods are used in some abbreviations (e.g., i.e., a.m., p.m.) and not in others (ac, dc, rpm). Most acronyms do not have periods. When you end a sentence with "etc." (although this is seldom necessary) or another abbreviation that already includes a period, do not add another one.

    Example:

    • This paper describes the program's purpose, objectives, schedule of deliverables, etc.
    • (Better: This paper describes the program's purpose, objectives, and schedule of deliverables.)

    personal pronouns

    First person pronouns should generally be avoided. However, some scientific and technical associations (such as the American Institute of Physics) ask technical writers to use first-person pronouns when it is appropriate. Common first-person pronouns include "we," "our," and "us." Personal pronouns can prevent confusion by clearly and concisely showing who performed an experiment or procedure.

    Examples:

    • We tested several hundred isolates that were able to ferment glucose.
    • We deposited a thin film of doped cadmium on the substrate.

    Which of these two sentences is easier to read and understand quickly?

    1. It was determined that the workshop was a success.
    2. We agreed that the workshop was a success.

    See also active voice and passive voice.

    phone numbers

    Do not use parentheses around area codes in phone numbers. Parentheses previously were used to set off the three-digit code in a phone number because it wasn't always necessary when dialing the number. However, they are required in most instances now.

    Use hyphens to separate the digits in phone numbers.

    Examples:

    • 303-275-3658
    • 1-800-555-5555

    photographs

    When you use an image, credit the photographer or other source for legal purposes. Provide a caption when necessary. See captions.

    photovoltaics and photovoltaic

    "Photovoltaics" is a singular noun. "Photovoltaic" is an adjective. The acronym "PV" can be a noun or an adjective, but do not pluralize it.

    policymaker

    "Policymaker" and "policymaking" are both spelled as one word. However, "decision maker" is two words.

    prefixes

    See compound words, unit modifiers, and hyphens and scientific notation.

    pressure

    Use the standard SI unit for pressure or stress, which is the pascal (Pa) or the bar. Non-SI units include psi (pounds per square inch), millimeters of mercury, torr, and atmospheres, and they are still in relatively widespread use.

    principal and principle

    "Principal" often means "chief" or "main," such as the principal investigator in a research project or the principal of a high school. "Principle" often refers to a belief, value, or rule.

    Back to Top | Topic Index

    quotation marks

    Use quotation marks for direct quotes and the titles of articles, papers, and reports. In print, use "curly" or "fancy" quotation marks.

    Examples:

    • "Let's meet again in 6 months," the chairman said, "to discuss our progress."
    • She presented a paper titled "Materials Research in Silvered Polymer Reflectors."

    Place commas (and periods) inside quotation marks; place semicolons, question marks, dashes, and exclamation points outside quotation marks unless they're part of the quotation.

    Examples:

    • "The results are in," he said.
    • "Can you hear me?" she asked.
    • Did he really say "I don't believe you"?

    Use single quotation marks to indicate a quotation within material that is already enclosed in double quotation marks.

    Example:

    • "Explain what you mean by 'confidence,'" she said.

    When quotations are longer than two or three lines of text, begin them on the next line and indent them on each side (block quotations). You do not need quotation marks around block quotations, and you can use standard double quotation marks for quotes within block quotations. In in-text quotations, place reference numbers, superscripts, and author-date citations outside quotation marks (but before the final punctuation of a sentence). Place them after the final punctuation of the last sentence in a block quotation.

    Back to Top | Topic Index

    Rankine cycle

    ratios

    In general, use a colon to indicate a ratio.

    Example:

    • We prepared a 3:1 dilution.

    However, some industries (such as the American automotive industry) use a solidus to express a ratio.

    Example:

    • The engine is designed to have an optimum air/fuel ratio.

    references

    Professional societies usually specify a style for references in papers published in their journals and proceedings. But if you're preparing a paper or report for EERE or for a publisher that has no prescribed style, you can use one of two basic formats for reference citations in text and the reference list at the end of your document: author-date references (EERE's preferred style) or numbered references. A reference list contains only the sources you cite in your paper or report. Include works not cited and sources of additional information in a bibliography.

    If you used author-date citations in text [for example, (Potter and Benson 1991)], arrange your reference list alphabetically according to the first author's last name. (Note that there is no comma between the names and the publication date in in-text citations.)

    If you used footnote or reference numbers/endnotes [1] in the text of your report or paper, use a numbered reference list, not one sorted alphabetically. The bracketed number should go inside the period when it is inserted as an in-text citation.

    Because many works/sources are now found and available online, some of the citation styles below show how to document an online source by providing a URL and the date accessed. Even if you didn't find/use the source online, it's still nice to provide readers with a URL if it's available online. If it's not available, then just omit that information from your citation.

    No Author

    You can adapt the "no author" style for any type of work/source. Just use the title in place of the author's name.

    Author-Date:

    Innovation EcoSystem Development Initiative. (2011). DOE/EE-6020. Washington, DC: U.S. Department of Energy. Accessed February 11, 2012:
    http://techportal.eere.energy.gov/commercialization/pdfs/innovation_ecosystem_factsheet.pdf.

    Numbered:

    1. Innovation EcoSystem Development Initiative. DOE/EE-6020. Washington, DC: U.S. Department of Energy, 2011. Accessed Feb. 11, 2012:
    http://techportal.eere.energy.gov/commercialization/pdfs/innovation_ecosystem_factsheet.pdf.

    Undated Material

    You can adapt this style for any type of work/source.

    Author-Date:

    Someone, R.U. (undated). How to Cite Undated Material. Somewhere, IN: The World Publishing.

    Numbered:

    2. Someone, R.U. How to Cite Undated Material. Somewhere, IN: The World Publishing (undated).

    Bill and Resolution

    Author-Date:

    U.S. Congress. (1985). Food Security Act of 1985. HR 2100. 99th Congress, first session, Congressional Record 131 (Oct. 8, 1985): H 8353-8486.

    Numbered:

    3. Food Security Act of 1985. H.R. 2100. 99th Congress, first session, Congressional Record 131 (Oct. 8, 1985): H 8353-8426.

    Book

    Author-Date:

    Perry, R.H; Chilton, C.H. (1973). Chemical Engineer's Handbook. 5th edition. New York: McGraw Hill. pp. 6-14.

    Numbered:

    4. Perry, R.H; Chilton, C.H. Chemical Engineer's Handbook. 5th edition. New York: McGraw Hill, 1973; pp. 6-14.

    Book Editor and Series

    Author-Date:

    Cooper, E.L., ed. (1974). Invertebrate Immunology. Contemporary Topics in Immunology, Vol. 4, New York: Plenum Publishing.

    Numbered:

    5. Cooper, E.L., ed. Invertebrate Immunology. Contemporary Topics in Immunology, Vol. 4, New York: Plenum Publishing, 1974.

    Chapter in a Book

    Author-Date:

    DeBlasio, R.; Stone, J.; Surek, T.; Emery, K.; Myers, D.; Kroposki, B.; Mrig, L.; Burdick, J.; Czanderna, A.; Strand, T.; Osterwald, C. (1995). "Photovoltaic Performance and Reliability," Chapter 5. Boer, K.W., ed. Advances in Solar Energy: An Annual Review of Research and Development. Vol. 10, Boulder, CO: American Solar Energy Society, Inc.; pp. 247-345.

    Numbered:

    6. DeBlasio, R.; Stone, J.; Surek, T.; Emery, K.; Myers, D.; Kroposki, B.; Mrig, L.; Burdick, J.; Czanderna, A.; Strand, T.; Osterwald, C. "Photovoltaic Performance and Reliability," Chapter 5. Boer, K.W., ed. Advances in Solar Energy: An Annual Review of Research and Development. Vol. 10, Boulder, CO: American Solar Energy Society, Inc., 1995; pp. 247-345.

    Conference/Technical Paper

    Author-Date:

    Lund, J.W. (January 2011). "Development of Direct-Use Projects." Preprint. Prepared for Stanford University Geothermal Reservoir Engineering Workshop, Jan. 31-Feb. 2, 2011. NREL/CP-5500-49948. Golden, CO: National Renewable Energy Laboratory, 8 pp. Accessed March 26, 2012: http://www.nrel.gov/docs/fy11osti/49948.pdf.

    Numbered:

    7. Lund, J.W. "Development of Direct-Use Projects." Preprint. Prepared for Stanford University Geothermal Reservoir Engineering Workshop, Jan. 31-Feb. 2, 2011. NREL/CP-5500-49948. Golden, CO: National Renewable Energy Laboratory, January 2011; 8 pp. Accessed March 26, 2012: http://www.nrel.gov/docs/fy11osti/49948.pdf.

    Conference Paper from Published Proceedings

    Author-Date:

    Hulstrom, R.L. (1985). "Solar Radiation Topical Overview." Photovoltaics and Insolation Measurements Workshop Proceedings; June 30-July 3, 1985, Vail, Colorado. SERI/CP-215-2773. Golden, CO: Solar Energy Research Institute; pp. 1-11.

    Numbered:

    8. Hulstrom, R.L. "Solar Radiation Topical Overview." Photovoltaics and Insolation Measurements Workshop Proceedings; June 30-July 3, 1985, Vail, Colorado. SERI/CP-215-2773. Golden, CO: Solar Energy Research Institute, 1985; pp. 1-11.

    Forthcoming Works

    Author-Date:

    Cory, K. (forthcoming). Feed-In Tariff Policy Design and Implementation: A Comprehensive Best Practices Guide.

    Numbered:

    9. Cory, K. Feed-In Tariff Policy Design and Implementation: A Comprehensive Best Practices Guide (forthcoming).

    Internal Reports or Unpublished Materials

    You can adapt this style for any type of non-EERE, unpublished materials. Just put "(unpublished)" or "(internal only)" at the end of the citation.

    Author-Date:

    NREL (2009). National Renewable Energy Laboratory FY 2008 Performance Self-Assessment Report. NREL/MP-700-43945. 91 pp. (internal only).

    Numbered:

    10. NREL. National Renewable Energy Laboratory Fiscal Year 2008 Performance Self-Assessment Report. NREL/MP-700-43945. 2009. 91 pp. (internal only).

    Journal Article

    Author-Date:

    Kharecha, P.A.; Kutscher, C.F.; Hansen, J.E.; Mazria, E. (2010). "Options for Near-Term Phaseout of CO2 Emissions from Coal Use in the United States." Environmental Science & Technology (44:11); pp. 4050-4062. Accessed March 26, 2012: http://pubs.acs.org/doi/pdfplus/10.1021/es903884a.

    Numbered:

    11. Kharecha, P.A.; Kutscher, C.F.; Hansen, J.E.; Mazria, E. "Options for Near-Term Phaseout of CO2 Emissions from Coal Use in the United States." Environmental Science & Technology (44:11), 2010; pp. 4050-4062. Accessed March 26, 2012: http://pubs.acs.org/doi/pdfplus/10.1021/es903884a.

    Newsletter Article

    Author-Date:

    "Uses of Petroleum." (April 1998). Connections: Energy, Environment, Economics and Education Working Together. Institute of Science and Public Affairs, Florida State University. Vol. 6, No. 3; p. 4.

    Numbered:

    12. "Uses of Petroleum." Connections: Energy, Environment, Economics and Education Working Together. Institute of Science and Public Affairs, Florida State University. Vol. 6, No. 3, April 1998; p. 4.

    Patent

    Author-Date:

    Baumann, B.D., et al., U.S. Patent No. 4,771,110 (Sept. 13, 1988).

    Numbered:

    13. Baumann, B.D., et al., U.S. Patent No. 4,771,110, Sept. 13, 1988.

    Presentation

    Author-Date:

    Rohrbach, R. (August 2006). "Desulfurization Fuel Filter." Presented at the 2006 Diesel Engine-Efficiency and Emissions Research Conference. Accessed March 26, 2012: http://www1.eere.energy.gov/
    vehiclesandfuels/pdfs/deer_2006/session7/2006_deer_rohrbach.pdf
    .

    Numbered:

    14. Rohrbach, R. "Desulfurization Fuel Filter." Presented at the 2006 Diesel Engine-Efficiency and Emissions Research Conference on Aug. 24, 2006. Accessed March 26, 2012: http://www1.eere.energy.gov/
    vehiclesandfuels/pdfs/deer_2006/session7/2006_deer_rohrbach.pdf
    .

    Personal Communication

    Author-Date:

    Smith, J.Q. (Feb. 28, 2013). Email to Roger, T., National Renewable Energy Laboratory. U.S. Department of Commerce, Washington, DC.

    Numbered:

    15. Smith, J.Q. Email to Roger, T., National Renewable Energy Laboratory. U.S. Department of Commerce, Washington, DC, Feb. 28, 2013.

    Private Communication

    Author-Date:

    Smith, J.Q. (Feb. 29, 1988). Internal memorandum. U.S. Department of Commerce, Washington, DC.

    Numbered:

    15. Smith, J.Q. Internal memorandum. U.S. Department of Commerce, Washington, DC, Feb. 29, 1988.

    Subcontract Report

    Author-Date:

    Bergman, R.; Paget, M.; Richman, M. (2011). CALiPER Exploratory Study: Accounting for Uncertainty in Lumen Measurements. PNNL-20320. Work performed by Rolf Bergman Consulting, Cleveland, OH. Richland, WA: Pacific Northwest National Laboratory. Accessed Feb. 21, 2013: http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/caliper_exploratory_lumen-uncertainty.pdf.

    Numbered:

    16. Bergman, R.; Paget, M.; Richman, M. CALiPER Exploratory Study: Accounting for Uncertainty in Lumen Measurements. PNNL-20320. Work performed by Rolf Bergman Consulting, Cleveland, OH. Richland, WA: Pacific Northwest National Laboratory, March 2011. Accessed Feb. 21, 2013: http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/caliper_exploratory_lumen-uncertainty.pdf.

    Technical Report

    Author-Date:

    Whalen, P.; Coburn, T.; Eudy, L. (1999). Perspectives on AFVs: State and City Government Fleet Manager Survey. NREL/TP-540-23980. Golden, CO: National Renewable Energy Laboratory. Accessed March 26, 2012: http://www.nrel.gov/docs/fy99osti/23980.pdf.

    Numbered:

    17. Whalen, P.; Coburn, T.; Eudy, L. Perspectives on AFVs: State and City Government Fleet Manager Survey. NREL/TP-540-23980. Golden, CO: National Renewable Energy Laboratory, 1999. Accessed March 26, 2012: http://www.nrel.gov/docs/fy99osti/23980.pdf.

    Thesis or Dissertation

    Author-Date:

    Gossett, J.M. (1976). The Treatment of Refuse for Increasing Anaerobic Biodegradability. Ph.D. Thesis. Stanford, CA: Stanford University.

    Numbered:

    18. Gossett, J.M. The Treatment of Refuse for Increasing Anaerobic Biodegradability. Ph.D. Thesis. Stanford, CA: Stanford University, 1976.

    Web Page

    Author-Date:

    "About the Solar Office." (2013). U.S. Department of Energy Solar Energy Technologies Office. Accessed Feb. 21, 2013: http://www1.eere.energy.gov/solar/sunshot/about.html.

    Numbered:

    19. "About the Solar Office." U.S. Department of Energy Solar Energy Technologies Office, 2013. Accessed Feb. 21, 2013: http://www1.eere.energy.gov/solar/sunshot/about.html.

    Work/Source Published in Same Year by Same Author

    Shown below is the style for citing a book by an author that has published another work listed in the references the same year. You can adapt this style for any type of work/source.

    Author-Date:

    _______________. (2006b). Solar Revolution: The Economic Transformation of the Global Energy Industry. Cambridge, MA: MIT Press.

    Numbered:

    N/A

    renewable energy certificate

    Don't capitalize "renewable energy certificate." It's not a proper noun. Also, this is the term preferred over "renewable energy credit" or "green tags."

    renewable portfolio standard

    Only capitalize "renewable portfolio standard" when a state name precedes it.

    • Renewable energy certificates have been proposed under California Renewable Portfolio Standards.

    restrictive phrases and clauses

    Do not use commas around restrictive phrases and clauses. They are essential to the meaning of the sentence, in contrast to nonrestrictive phrases and clauses, which simply add information that is not essential.

    Example:

    • This is the house that Jack built.

    See also which and that.

    rheology

    Back to Top | Topic Index

    scientific notation

    Standard scientific notation represents a number as a factor multiplied by a power of 10; 3,560,000 is expressed as 3.56 × 106. This is useful for very large and very small numbers, especially in non-SI units. You can also use certain standard prefixes, many of which are listed here with their abbreviations.

    1024 yotta Y
    1021 zetta Z
    1018 exa E
    1015 peta P
    1012 tera T
    109 giga G
    106 mega M
    103 kilo k
    102 hecto h
    101 deka da
    10-1 deci d
    10-2 centi c
    10-3 milli m
    10-6 micro µ
    10-9 nano n
    10-12 pico p
    10-15 femto f
    10-18 atto a
    10-21 zepto z
    10-24 yocto y

    We recommend choosing a prefix that permits the numerical value to fall between 0.1 and 1,000 (62 kW rather than 62,000 W).

    semicolons

    Semicolons indicate a stronger or more important break in the flow of words than the break indicated by a comma. Use a semicolon in compound sentences that are NOT linked by a conjunction (such as "and," "but," "or," "nor," and "yet"). Place a semicolon before conjunctive adverbs (such as "however," "hence," "therefore," "nevertheless," "consequently") in most complex sentences containing two or more clauses. When a sentence contains items in a series, you may use a semicolon between the items if one or more of the items contains commas.

    1. Using Semicolons in Compound Sentences Without Conjunctions

      When clauses in a sentence are closely related in meaning, a semicolon is an appropriate dividing punctuation mark. Note that the words "and," "but," "or," and "nor" do not follow semicolons.

      Example:

      • It was difficult to reproduce the experiment; the material Smith and Jones used was not widely available. Of the 13 samples, only one did not degrade; others deteriorated an average of 8%.

    2. Using Semicolons With Conjunctive Adverbs

      "Yet" and "so" are usually preceded by commas in a complex sentence. But use a semicolon before such conjunctive adverbs as "then," "however," "thus," "therefore," "hence," "accordingly," "moreover," "nevertheless," "consequently," "besides," "indeed," and "subsequently"; place a comma after the adverb.

      Examples:

      • The contractor's representative was out, so I left a message.

      • We used the Schartz-Metterklume method in the experiment; however, the problems with this method are well known.

      • Energy requirements are often expressed in quads, or quadrillion Btu; therefore, this report describes the number of quads supplied annually by each option.

      Use a semicolon before "i.e." ("that is") and "e.g." ("for example") and a comma after them when a clause (with a subject and verb) follows them; use a comma when a phrase or list follows.

    3. Using Semicolons in a Series

      When items in a series contain internal punctuation (e.g., commas) or are very long, you can separate them with semicolons. In those cases, a conjunction can follow the last semicolon.

      Examples:

      • The contaminants in the sample were TCE, 150 ppb; toluene, 220 ppb; and benzene, 265 ppb.

      • Promising new technologies demonstrated at the exposition included advanced wind turbines; polycrystalline, thick-film, and thin-film solar cells; fast-growing energy crops; and fuel cells.

      • The vendor assured us that the replacement parts, which were essential in this installation, were on order; that the parts would be delivered as soon as they arrived; and that the delay in shipment was unavoidable.

    SI (metric) system

    EERE follows national policies and those of scientific societies by using the SI (Systeme International d'Unites; International System of Units) or metric system in expressing technical measurements. English units may follow metric ones or may be used alone in special cases, when that is appropriate for a publication's audience. See also the National Institute of Standards and Technology.

    since and because

    See because and since.

    slash (solidus)

    The solidus (or slash, slant, shilling mark, or virgule) is a versatile symbol that has mathematical as well as textual functions.

    1. Using a Solidus in Fractions

      Use a solidus to express a quotient in text when you do not need to use a displayed equation.

      Example:

      • These structures yield photoluminescence lifetimes that are related to bulk lifetime by the expression Expression reading one over tau equals one over tau sub R plus two times sigma over delta..

      Use a solidus in superscript and subscript fractions.

      Example:

      • x1/2
    2. Using a Solidus in Text

      In text, use a solidus to indicate some junctions, interfaces, and components.

      Examples:

      • gas-liquid interface
      • 1-butyl acetate/acetic acid/water (3:1:1)

      With abbreviated units of measurement, the solidus stands for "per."

      Examples:

      • 2 g/cm2
      • 355 W/m2

      But spell out "per" when you spell out the units of measurement.

      Examples:

      • several cubic meters per second
      • a few cents per kilowatt-hour

    Smart Grid and smart grid

    Use capital letters for "Smart Grid" when referring to the overall goal or concept and lowercase letters for "smart grid" when referring to current implementations or when used as an adjective.

    solar cell interfaces

    Use a slash rather than a hyphen to designate solar cell interfaces or layers.

    Examples:

    • CdTe/CdS2
    • GaInP/GaAs2

    solar conversion efficiency

    Define in outreach publications as "the percentage of sunlight striking a solar cell that is converted into electricity." A definition is often unnecessary in technical publications.

    solar electricity

    This term can be used interchangeably with "photovoltaic power," "PV power," or "PV electricity."

    sources

    Include the sources of all figures and tables that were originally published by others, especially those outside EERE. If figures or tables come from a copyrighted publication, you may need permission to reproduce them. Add the source at the end of a figure caption or in a note following a table.

    Example:

    • Source: Hansen, W.L.; Pearton, S.J.; Haller, E.E. (1984). Appl Phys. Lett. 44:606.

    spaces

    Use only one space between a period and the beginning of the next sentence.

    spelling

    If you can't find a word or phrase in this style guide, consult the following reference guides in this order: (1) The Associated Press Stylebook 2007 and (2) Merriam-Webster's Collegiate Dictionary, Eleventh Edition.

    For spelling out numbers, see numbers.

    standard errors

    Express standard measurement errors as shown below.

    Example:

    • 6.0 nm ± 0.2 nm

    state implementation plan

    Capitalize "state implementation plan" only when a state or organization name precedes it.

    Example:

    • The Connecticut Department of Environmental Protection incorporated emission reduction strategies into its U.S. Environmental Protection Agency State Implementation Plan for air quality.

    states and countries

    1. States

      In text, consistently spell out states' names rather than using U.S. Postal Service abbreviations.

      Examples:

      • California (rather than CA)
      • Colorado (rather than CO)
      • Wyoming (rather than WY)

      You may use D.C. for the District of Columbia in text, in both formal and informal publications. When you include addresses or state names in full addresses (containing streets and cities), contact lists, reference lists, and bibliographies, however, you may use the following abbreviations:

      AL, AK, AZ, AR, CA, CO, CT, DC, DE, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VT, VA, WA, WV, WI, WY (PR, VI).

    2. Countries

      Do not abbreviate the names of countries (including the United States) when they are used as nouns. Use U.S. as the adjective form.

      Examples:

      • the United States
      • U.S. DOE program
      • U.S. population

    statistical terms

    When referring to statistical or graphical terms, use a hyphen but no italics. Also, do not use capital letters.

    Examples:

    • p-value
    • t-test
    • y-axis

    supercritical fluid

    systems integrator

    The correct term is "systems integrator," not "system integrator."

    Back to Top | Topic Index

    taxonomic names

    See capitalization and italics.

    temperature

    Use a degree symbol (º) with temperatures expressed in the Celsius and Fahrenheit scales but not with kelvins (just use K). Don't leave a space between the number and the letter for ºC and ºF, but leave a space between the number and K.

    Examples:

    • 72°F
    • 0 K

    See also degree symbol.

    that and which

    See which and that, nonrestrictive phrases and clauses, and restrictive phrases and clauses.

    III-V solar cell

    This term refers to a cell composed of semiconducting materials from Group III (e.g., gallium) and Group V (e.g., arsenic) elements of the periodic table.

    time

    Use lowercase a.m. and p.m. (with periods) to denote "ante meridiem" and "post meridiem" (before and after noon); use a lowercase s (no apostrophe) to show the plural of a decade expressed with numerals (the 1990s).

    trademark symbols

    Do not use trademark symbols (® or ™) with third-party products.

    Back to Top | Topic Index

    under and over

    See over and under.

    unit modifiers

    See compound words, unit modifiers, and hyphens.

    United States and U.S.

    Spell out "United States" when it is used as a noun. The abbreviation "U.S." is acceptable when it is used as an adjective.

    Examples:

    • The United States is a leader in renewable energy markets.
    • The global markets for renewable energy are stronger than the U.S. markets.

    units of measurement

    Use numerals with units of measurement and time in technical papers and reports, even when the number is less than 10. In some outreach publications, you may spell out numbers less than 10, especially with units of time. Except with $, °, and %, leave a space between the numeral and the unit.

    2 kW 7 cm2 16.8%
    3 m 8-hour days 300 Btu
    5 years $2 billion 45°

    URLs

    Uniform resource locators, or URLs, are essentially Web addresses.

    On websites, URLs should be embedded in text.

    Example:

    In print, URLs should not be embedded in text. If a URL extends beyond one line of text, add a break at a solidus. Also, in general, you do not need to include the http:// prefix on most URLs - but test it before removing it. Shorten URLs as much as possible (e.g., remove unnecessary trailing such as /index.html) while ensuring functionality.

    U.S. Department of Energy

    When spelling it out, "U.S." should precede "Department of Energy." However, "U.S." should not be included with the acronym "DOE."

    If the possessive is used with the term, the apostrophe should go after "U.S. Department of Energy" and with the "DOE" acronym as well. However, if you can write it in a way that avoids use of the possessive, that is preferred.

    Example:

    • The U.S. Department of Energy's (DOE's) Office of Energy Efficiency and Renewable Energy (EERE) is in charge of the program.

    Back to Top | Topic Index

    watt

    Web terms

    "Web" is not capitalized when it is part of a compound word. The following words are lower case:

    • website
    • webmaster
    • webinar
    • webcast.

    "Web" is the short form of World Wide Web, which is a proper noun. Therefore, when referring to the Web or using terms with separate words, use upper case "Web." For example:

    • Web page
    • the Web
    • Web feed.

    which and that

    Standard American English uses "which" for nonrestrictive or nondefining phrases and clauses and "that" for restrictive or defining phrases and clauses. The word "which" usually signals the approach of added, nonessential information. When a phrase or clause is not essential to the meaning of a sentence, use the relative pronoun "which" and enclose the phrase or clause in commas. See also nonrestrictive phrases and clauses and restrictive phrases and clauses.

    Example:

    • This paper, which she has been working on for three weeks, discusses string theory.

    When a phrase or clause is essential to the meaning of a sentence (that is, the sentence would not make much sense without it), use "that" and leave out the commas.

    Example:

    • The paper that he completed recently will be presented in New York; the paper that he finished last summer will be presented in Philadelphia.

    work-for-others agreement

    Use lowercase for "work-for-others agreement" because it's not a proper noun. The acronym "WFO" refers only to work for others; therefore, when using the acronym, "WFO agreement" is correct.

    World Wide Web

    To abbreviate World Wide Web use "Web," after writing the name out in full the first time it is mentioned.

    years and months

    See months and years.

    zero

    For numbers less than one, place a zero before the decimal.

    Examples:

    • 0.5
    • 0.125
    • 0.00125

    zero-energy building

    Do not use the term "net zero" and "net zero energy" when referring to buildings that use both energy efficiency and renewable energy sources to offset or mitigate building energy use. These terms should be replaced with the term "ultra high efficiency" or "ultra-efficient building" when used in this context.

    Back to Top | Topic Index