U.S. Department of Energy - Energy Efficiency and Renewable Energy

Federal Energy Management Program

Covered Product Category: Commercial Boiler

  • Did you know? - Modular Is Efficient
    It is more efficient to operate several small, modular boilers than a single large boiler.

  • Did You Know? - Condensing Boilers Are 10% More Efficient
    Condensing boilers utilize some of the latent heat component of a fuel source in addition to most of the sensible. By doing so, the efficiency of these boilers can be up to 10% greater than non-condensing models.

  • Did You Know? - What's Covered
    All Federal purchases of hot water or steam boilers (using either oil or gas) with a rated capacity (Btu/h) of 300,000-10,000,000 must meet or exceed FEMP-designated thermal efficiencies.

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Updated December 2011

FEMP provides acquisition guidance and Federal efficiency requirements across a variety of product categories, including commercial boilers, which are a FEMP-designated product category. Federal laws and executive orders mandate that agencies meet these efficiency requirements in all procurement and acquisition actions that are not specifically exempted by law.

These acquisition guidance and efficiency requirements apply to low-pressure boilers used in commercial space heating applications. High-pressure boilers (i.e., those used in industrial and cogeneration applications) and residential boilers (i.e., those less than 300,000 Btu/h) are excluded. Specify boilers that meet the thermal efficiency requirements shown in table 1. Condensing boilers are inherently more efficient than non-condensing boilers and should be procured whenever appropriate.

Federal agencies are required by the National Energy Conservation Policy Act (P.L. 95-619), Executive Order 13423, Executive Order 13514, and Federal Acquisition Regulations (FAR) Subpart 23.2 and 53.223 to specify and buy ENERGY STAR®-qualified products or, in categories not included in the ENERGY STAR program, FEMP-designated products, which are among the highest 25% of equivalent products for energy efficiency.

This product category overview covers the following:

Energy Efficiency Requirements for Commercial Boilers

Due to their high efficiencies, condensing boilers should be purchased whenever appropriate for the application. Non-condensing boilers are inherently less efficient than condensing models and should only be used in applications where condensing boilers will not work properly. FEMP-designated efficiency requirements for both condensing and non-condensing boilers can be found in table 1 below.

Condensing boilers can typically be used in new construction or renovations that replace the heat distribution systems. Condensing boilers may also be appropriate in other renovations or replacement scenarios, but in these cases, detailed engineering analyses should be used to determine if the heat distribution systems can function properly.1 If an engineering analysis determines that a heat distribution system is incompatible with condensing boiler operation, an efficient non-condensing model should used.

1 If conducting a detailed engineering analysis, consider whether the system can maintain the supply and return water temperatures required for efficient operation of condensing boilers, while still functioning properly.

Table 1 displays the minimum efficiency for multiple types of commercial boilers. All Federal purchases of hot water or steam boilers (using either oil or gas) with a rated capacity (Btu/h) of 300,000-10,000,000 must meet or exceed the thermal efficiencies listed in table 1 below.

Table 1. Efficiency Requirements for Federal Purchases of Commercial Boilers
Boiler Type (Fuel) Rated Capacity (Btu/h) Thermal Efficiency1
Hot Water, Condensing (Oil or Gas) 300,000-10,000,000 94% or greater
Hot Water, Non-Condensing (Oil) 300,000-10,000,000 85% or greater
Hot Water, Non-Condensing (Gas) 300,000-10,000,000 84% or greater
Steam (Oil) 300,000-10,000,000 83% or greater
Steam (Gas) 300,000-10,000,000 80% or greater

1 Based on Hydronic Institute, Method to Determine Efficiency of Commercial Space Heating Boilers (HI BTS-2000, Rev06.07)

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Determining Cost Effectiveness

An efficient product is cost effective when the energy cost savings over its functional lifetime exceed any initial incremental cost above a base model (i.e., energy cost savings is greater than additional costs at time of purchase). Federal purchasers may assume that products meeting FEMP-designated efficiency requirements are life-cycle cost effective. However, users wishing to determine cost effectiveness for their application may do so using the cost effectiveness example in table 2.

Products meeting FEMP-designated efficiency requirements or ENERGY STAR performance specifications may not be life-cycle cost effective when energy rates are below the Federal average or in certain low-use applications, such as when a device will remain in off mode for most of its useful life. For most applications, purchasers will find that energy-efficient products have the lowest life-cycle cost. In high-use applications or when energy rates are above the Federal average, purchasers may save more if they specify products that exceed the Federal efficiency requirements, as shown in the Best Available column in table 2.

The cost effectiveness example provided in table 2 is for a 1,000,000 Btu/h gas-fired, hot water boiler operated for 1,500 full-load hours per year. The performance of the standard unit is based on ASHRAE 90.1-2007, the required non-condensing unit meets FEMP's efficiency requirements for non-condensing boilers, and the required condensing column meets FEMP's efficiency requirements for condensing boilers. The performance of both the best available non-condensing and condensing units is from the AHRI Directory of Certified Products.

Table 2. Cost Effectiveness Example for Commercial Hot Water Boilers (Gas)
Performance Standard Required Non-Condensing Best Available Non-Condensing Required Condensing Best Available Condensing
Thermal Efficiency (Et) 80% 84% 86% 94% 96%
Annual Energy Use (therm) 18,750 therm 17,855 therm 17,445 therm 16,305 therm 15,955 therm
Annual Energy Cost $16,875 $16,070 $15,700 $14,675 $14,360
Lifetime Energy Cost $305,605 $291,050 $284,285 $265,740 $260,085
Lifetime Energy Cost Savings - $14,555 $21,320 $39,865 $45,520

The assumed price for natural gas is $0.90 per therm, the average at Federal facilities in the United States. Lifetime energy cost is the sum of the discounted value of annual energy cost for an assumed boiler life of 25 years. Future natural gas price trends and a 3% discount rate are from the Price Indices and Discount Factors for Life-Cycle Cost Analysis.

Operating conditions vary from facility to facility. To help determine cost effectiveness in operating conditions different from the example, FEMP provides an interactive cost calculator.

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Contracting Considerations

These requirements apply to all forms of procurement, including construction guide specifications and project specifications; renovation, repair, maintenance, and energy service contracts; lease agreements; acquisitions made using purchase cards; and solicitations for offers. Energy efficiency requirements should be included in both the evaluation criteria of solicitations and the evaluations of solicitation responses.

Federal Acquisition Regulation (FAR) Part 23.206 requires Federal agencies to insert the clause at FAR section 52.223-15 in solicitations and contracts that deliver, acquire, furnish, or specify energy-consuming products. FEMP recommends that agencies incorporate efficiency requirements into both the technical specification and evaluation sections of solicitations. Agencies may claim an exception to these requirements through a written finding that no ENERGY STAR-qualified or FEMP-designated product is available to meet the functional requirements, or that no such product is life-cycle cost effective for the specific application. Additional information on Federal requirements is available.

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Buyer Tips: How to Choose Efficient Products

A boiler system should be capable of meeting the building's peak heating demand and also operate efficiently at part-load conditions. Selecting the right system and properly sizing a boiler requires knowledge of both the peak demand and load profile. If building loads are highly variable, as is common in commercial buildings, designers should consider installing multiple small (modular) boilers in addition to boilers that have modulating burners. In periods of low demand, some of the boilers can be isolated from the other boilers and not incur any standby losses or cycling losses. They can also be automatically staged such that each boiler is running at its most efficient operating point without incurring additional cycling.

For guidance on boiler rightsizing and quality installation, consult the American National Standards Institute/Air Conditioning Contractors of America Standard 5: HVAC Quality Installations Specification (ANSI/ACCA 5 QI 2010).

Federal procurement officers and buyers should consider specifying boilers with the following features:

  • Water temperature reset-Hot water boilers should have the capability for water temperature reset. This is typically based on the outdoor air temperature or the return water temperature. When the heating load is reduced, the supply water is set to a lower temperature.

  • Modulating burners-It is recommended that boilers have the capability to vary their heating output by modulating the burner. Most of the time boilers operate at part load. To prevent excessive cycling and the losses that accompany them, specify boilers that have modulating capability. A minimum turndown ratio of 4:1 is recommended for gas/water boilers. This is particularly important in condensing boilers that run more efficiently at part load.

  • Low mass-Because boilers cycle on and off and it takes time to bring a high mass boiler up to operating temperature, using loss-mass boilers will reduce energy consumption. In addition, some boilers can be brought online quickly, therefore avoiding the need to keep a boiler on hot standby.

  • Remote monitoring capability-Remote monitoring capability is useful to manage boiler operation and to detect any malfunctions in a timely manner.

  • Precise air-fuel ratio control-It is important to keep the air-fuel ratio at optimum levels at part-load operation as well as full-load operation. This is better accomplished by using sensor-driven servos rather than a mechanical linkage (e.g., jack shaft) between the gas input and the blower damper. Oxygen trim systems should be used on larger boilers. Oxygen trim systems monitor the oxygen in the flue gas and adjust the air-fuel ratio for optimum combustion efficiency.

  • Optimum start control-An optimum start control fires up a boiler so that it fires just in time to heat up a building before it is occupied in the morning.

  • Other enhancements-Other options to increase efficiency of the heating system include reusing heat from blow down and return condensate for steam boilers, use of electronic ignition devices and increasing boiler and piping insulation.

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User Tips: How to Use Products More Efficiently

Several diagnostic and maintenance procedures are important to maintaining efficient boiler operation. Flue gas temperature monitoring is useful in detecting efficiency and operating problems. Maintaining steady excess air levels (with an oxygen trim sensor) ensures that burners will mix air and fuel properly. Low water levels can damage boilers so water levels should be checked frequently, as part of a regular maintenance program. Water treatment can prolong boiler life as well as increase its efficiency. Waterside and fireside surfaces should be cleaned annually.

The Boiler Efficiency Institute provides maintenance and operation manuals for boilers and boiler control systems. To encourage quality operations and maintenance, building engineers can also refer to ASHRAE/ACCA Standard 180: Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems. In addition, the FEMP O&M Best Practices Guide, Release 3.0, Chapter 9 provides valuable information on operation and maintenance of boiler systems.

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For More Information

The following resources provide additional information surrounding the purchase of efficient products:

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