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External Power Supplies

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External power supplies (EPS) convert household electric current into direct current or lower-voltage alternating current to operate a consumer product such as a laptop computer or smart phone. There are hundreds of product types that use an EPS and over 300 million EPSs are shipped each year. Energy conservation standards have been in place for external power supplies since 2007.

The standards implemented in 2007 will save approximately 3.8 quads of energy and result in approximately $42.4 billion in energy bill savings for products shipped from 2008-2032. The standard will avoid about 198.5 million metric tons of carbon dioxide emissions, equivalent to the annual greenhouse gas emissions of about 39 million automobiles.

The standards implemented in 2014 will save consumers up to an additional $3.8 billion and cut emissions by nearly another 47 million metric tons of carbon dioxide over 30 years, equivalent to the annual electricity use of 6.5 million homes.


Recent Updates | Standards | Test Procedures | Waiver, Exception, and Exemption Information | Statutory Authority | Historical Information | Contact Information


Recent Updates

DOE published a final rule prescribing new energy conservation standards for external power supplies. 79 FR 7845 (February 10, 2014). This new standard applies to all direct operation External Power Supplies and includes, in addition to Class A power supplies previously covered by 2007 standards, power supplies that have not previously been subject to DOE regulations, such as multiple-voltage EPSs, EPSs with nameplate output power greater than 250 watts, and some EPSs that charge the battery of a product that is fully or primarily motor operated. For more information, please see the rulemaking page.


Standards for External Power Supplies

The following content summarizes the energy conservation standards for external power supplies. The text is not an official reproduction of the Code of Federal Regulations and should not be used for legal research or citation.

Current Standard

Direct Operation EPS Standards

The new efficiency standards for EPSs established efficiency standards for Direct Operation External Power Supplies. All direct operation external power supplies manufactured on or after two years after the final rule’s date of publication in the Federal Register shall meet the following standards:

Direct Operation External Power Supply Efficiency Standards
Single-Voltage External AC-DC Power Supply, Basic-Voltage
Nameplate Output Power (Pout) Minimum Average Efficiency in Active Mode
(expressed as a decimal)
Maximum Power in No-Load Mode [W]
Pout less than equal to sign 1 W greater than equal to sign 0.5 × Pout + 0.16 less than equal to sign 0.100
1 W < Pout less than equal to sign 49 W greater than equal to sign 0.071 × ln(Pout) - 0.0014 × Pout + 0.67 less than equal to sign 0.100
49 W < Pout less than equal to sign 250 W greater than equal to sign 0.880 less than equal to sign 0.210
Pout > 250 W greater than equal to sign 0.875 less than equal to sign 0.500
Single-Voltage External AC-DC Power Supply, Low-Voltage
Nameplate Output Power (Pout) Minimum Average Efficiency in Active Mode
(expressed as a decimal)
Maximum Power in No-Load Mode [W]
Pout less than equal to sign 1 W greater than equal to sign 0.517 × Pout + 0.087 less than equal to sign 0.100
1 W < Pout less than equal to sign 49 W greater than equal to sign 0.0834 × ln(Pout) - 0.0014 × Pout + 0.609 less than equal to sign 0.100
49 W < Pout less than equal to sign 250 W greater than equal to sign 0.870 less than equal to sign 0.210
Pout > 250 W greater than equal to sign 0.875 less than equal to sign 0.500
Single-Voltage External AC-AC Power Supply, Basic-Voltage
Nameplate Output Power (Pout) Minimum Average Efficiency in Active Mode
(expressed as a decimal)
Maximum Power in No-Load Mode [W]
Pout less than equal to sign 1 W greater than equal to sign 0.5 × Pout + 0.16 less than equal to sign 0.210
1 W < Pout less than equal to sign 49 W greater than equal to sign 0.071 × ln(Pout) - 0.0014 × Pout + 0.67 less than equal to sign 0.210
49 W < Pout less than equal to sign 250 W greater than equal to sign 0.880 less than equal to sign 0.210
Pout > 250 W greater than equal to sign 0.875 less than equal to sign 0.500
Single-Voltage External AC-AC Power Supply, Low-Voltage
Nameplate Output Power (Pout) Minimum Average Efficiency in Active Mode
(expressed as a decimal)
Maximum Power in No-Load Mode [W]
Pout less than equal to sign 1 W greater than equal to sign 0.517 × Pout + 0.087 less than equal to sign 0.210
1 W < Pout less than equal to sign 49 W greater than equal to sign 0.0834 × ln(Pout) - 0.0014 × Pout + 0.609 less than equal to sign 0.210
49 W < Pout less than equal to sign 250 W greater than equal to sign 0.870 less than equal to sign 0.210
Pout > 250 W greater than equal to sign 0.875 less than equal to sign 0.500
Multiple-Voltage External Power Supply
Nameplate Output Power (Pout) Minimum Average Efficiency in Active Mode
(expressed as a decimal)
Maximum Power in No-Load Mode [W]
Pout less than equal to sign 1 W greater than equal to sign 0.497 × Pout + 0.067 less than equal to sign 0.300
1 W < Pout less than equal to sign 49 W greater than equal to sign 0.075 × ln(Pout) + 0.561 less than equal to sign 0.300
Pout > 49 W greater than equal to sign 0.860 less than equal to sign 0.300

Definitions

Single-voltage external AC-DC power supply means an external power supply that is designed to convert line voltage AC into lower-voltage DC output and is able to convert to only one DC output voltage at a time.

Single-voltage external AC-AC power supply means an external power supply that is designed to convert line voltage AC into lower-voltage AC output and is able to convert to only one AC output voltage at a time.

Multiple-voltage external power supply means an external power supply that is designed to convert line voltage AC input into more than one simultaneous lower-voltage output.

Low-voltage external power supply means an external power supply with a nameplate output voltage less than 6 volts and nameplate output current greater than or equal to 550 milliamps. Basic-voltage external power supply means an external power supply that is not a low-voltage power supply.

Direct operation external power supply means an external power supply that can operate a consumer product that is not a battery charger without the assistance of a battery.

Indirect operation external power supply means an external power supply that cannot operate a consumer product that is not a battery charger without the assistance of a battery. DOE has established the following steps to determine if an EPS is a direct or indirect operation EPSs.

METHOD TO DISTINGUISH BETWEEN DIRECT AND INDIRECT OPERATION EPSs

(1) If the external power supply (EPS) can be connected to an end-use consumer product and that consumer product can be operated using battery power, the method for determining whether that EPS is incapable of operating that consumer product directly is as follows:

Step (i) If the end-use product has a removable battery, remove it for the remainder of the test and proceed to step (v). If not, proceed to step (ii).

Step (ii) Charge the battery in the application via the EPS such that the application can operate as intended before taking any additional steps.

Step (iii) Disconnect the EPS from the application. From an off mode state, turn on the application and record the time necessary for it to become operational to the nearest five second increment (5 sec, 10 sec, etc.).

Step (iv) Operate the application using power only from the battery until the application stops functioning due to the battery discharging.

Step (v) Connect the EPS first to mains and then to the application. Immediately attempt to operate the application. If the battery was removed for testing and the end-use product operates as intended, the EPS is not an indirect operation EPS and paragraph 2 of this definition does not apply. If the battery could not be removed for testing, record the time for the application to become operational to the nearest five second increment (5 seconds, 10 seconds, etc.).

(2) If the time recorded in paragraph (1)(v) is greater than the summation of the time recorded in paragraph (1)(iii) of this definition and five seconds, the EPS cannot operate the application directly and is an indirect operation EPS.

Exemptions from the Direct Operation EPS Standard

The direct operation EPS standards do not apply if:

  • It is a device that requires Federal Food and Drug Administration listing and approval as a medical device in accordance with section 360c of title 21; or
  • A direct operation, AC-DC external power supply with nameplate output voltage less than 3 volts and nameplate output current greater than or equal to 1,000 milliamps that charges the battery of a product that is fully or primarily motor operated.

Rulemaking Documents

After a regulatory action has been completed, Executive Order 12866 requires agencies to identify the substantive changes between the draft submitted to Office of Information and Regulatory Affairs (OIRA) for review and the action subsequently announced, and to identify those changes made at the suggestion or recommendation of OIRA.

Class A EPS Efficiency Standards

The efficiency standards above apply to all direct operation EPSs. Additionally, the Class A EPSs efficiency standards remain in effect, so all Class A EPSs manufactured and distributed in commerce, as defined by 42 U.S.C. 6291 (16), on or after July 1, 2008 must meet the energy conservation standards specified in the Code of Federal Regulations, 10 CFR 430.32(w). Since the direct operation EPS standards are more stringent than the Class-A EPS standards, a direct operation EPS that meets the new direct operation standards would also meet the Class A efficiency standards. However, a Class-A EPS that is exempt from the direct operation EPS standards (i.e. an indirect operation EPS) would still be required to meet these Class-A EPS efficiency standards.

Class A External Power Supply Efficiency Standards
Active Mode
Nameplate output Required efficiency (decimal equivalent of a percentage)
Less than 1 watt 0.5 times the Nameplate output
From 1 watt to not more than 51 watts The sum of 0.09 times the Natural Logarithm of the Nameplate Output and 0.5
Greater than 51 watts 0.85
No-Load Mode
Nameplate output Maximum consumption
Not more than 250 watts 0.5 watts

Definitions

The term "class A external power supply" means a device that—

  • is designed to convert line voltage AC input into lower voltage AC or DC output;
  • is able to convert to only 1 AC or DC output voltage at a time;
  • is sold with, or intended to be used with, a separate end-use product that constitutes the primary load;
  • is contained in a separate physical enclosure from the end-use product;
  • is connected to the end-use product via a removable or hard-wired male/female electrical connection, cable, cord, or other wiring; and
  • has nameplate output power that is less than or equal to 250 watts.

The term "class A external power supply" does not include any device that—

  • requires Federal Food and Drug Administration listing and approval as a medical device in accordance with section 360c of title 21; or
  • powers the charger of a detachable battery pack or charges the battery of a product that is fully or primarily motor operated.

Rulemaking Documents

Labeling Requirements

Any external power supply subject to the federal efficiency standards shall be clearly and permanently marked in accordance with the International Efficiency Marking Protocol for External Power Supplies Version 3.0, updated in September 2013. This new version of the Protocol provides additional flexibility on where the marking may be placed.

Test Procedure for External Power Supplies

Current Test Procedure

To determine compliance with DOE standards, manufacturers must follow the test procedures specified at 10 CFR 430.23(bb) for and external power supplies. The methods to conduct the test procedure for external power supplies are further specified in 10 CFR Part 430 Appendix Z to Subpart B . These are also in the Electronic Code of Federal Regulations.

For further guidance or to submit questions related to the implementation of this test procedure, visit the Guidance and Frequently Asked Questions page.

Waivers, Exceptions, and Exemptions

Waivers

Test procedure waivers have not been issued for external power supplies.

For information about obtaining test procedure waivers, see 10 CFR section 430.27.

Exceptions

DOE's Office of Hearings and Appeals has not authorized exception relief for battery chargers nor for external power supplies.

For information about obtaining exception relief, see 10 CFR part 1003.

State Exemptions to Federal Pre-emption

DOE has not exempted any state from this energy conservation standard. States may petition DOE to exempt a state regulation from preemption by the federal energy conservation standard. States may also petition DOE to withdraw such exemptions. For details, see 10 CFR part 430, subpart D.

Small Business Exemptions

Any manufacturer of a covered product with annual gross revenues that do not exceed $8,000,000 from all its operations and meets certain other conditions may apply for an exemption to the energy conservation standard. For details, see 10 CFR part 430, subpart E.

Congressionally Mandated Exemptions

Certain external power supplies used in security and life safety alarms and surveillance systems are exempt from the no-load mode power requirements that apply generally to Class A external power supplies. This exemption took effect on October 19, 2011. For details, see 76 FR 57897 (September 19, 2011).

The Energy Policy and Conservation Act (EPCA) also provides an exemption from standards for any Class A external power supply manufactured between July 1, 2008 and June 30, 2015 that is made available as a service part or a spare part (replacement part) for an end-use product manufactured before July 1, 2008. For details, see 76 FR 57897; 57899-57900.

Statutory Authority

The current energy conservation standards for battery chargers and external power supplies are mandated by Part A, the ‘‘Energy Conservation Program for Consumer Products Other Than Automobiles’’ of Title III of the Energy Policy and Conservation Act (EPCA), as amended. (42 U.S.C. § 6291–6309) These appliances are treated as covered products’ under Part A. (42 U.S.C. 6295(u))

Historical Information

The Energy Policy Act of 2005 (EPACT 2005) and the Energy Independence and Security Act of 2007 (EISA 2007) amended EPCA with regard to the energy conservation program for battery chargers and external power supplies.

EPCA, as amended by EPACT 2005 and EISA 2007, sets efficiency standards for Class A external power supplies and mandates various rulemaking activities. (42 U.S.C. 6295(u)(3))

The statute also requires DOE to issue a final rule prescribing energy conservation standards for battery chargers (42 U.S.C. 6295(u)(1)(E)(i)(II) as well as perform a determination analysis for external power supplies excluded from the July 1, 2008, standard. (42 U.S.C. 6295(u)(1)(E)(i)(I) These rulemakings were previously bundled with the rulemaking for Class A electronic power supplies, as the products are closely related. However, after further analysis DOE has decided to split these two products. Please see the battery charger product page for further information on battery chargers.

Previous Test Procedure Rulemakings

2009 Final Rule

2006 Final Rule

Other Previous Rulemakings

EISA 2007 Non-Class A EPS Determination Analysis

EPACT 2005 Battery Charger and External Power Supply Determination Analysis

Helpful Links and Contact Information

Helpful Links

Find tips and guidance for making your home, workplace, or vehicle more energy efficient visit EnergySaver.gov.

DOE supports the testing and verification of ENERGY STAR® products in close collaboration with the Environmental Protection Agency. ENERGY STAR qualified battery chargers are on average 35 percent more energy efficient than standard models.

Contact information

For more information related to the regulation of this product, please email:


battery_chargers_and_external_power_supplies@ee.doe.gov