The Federal Energy Management Program (FEMP) provides acquisition guidance for whole-home gas tankless water heaters, which are an ENERGY STAR-qualified product category. Federal laws and requirements mandate that agencies meet these efficiency requirements in all procurement and acquisition actions that are not specifically exempted by law.
Most manufacturers display the ENERGY STAR label on complying models. For a model not displaying this label, check the manufacturer's literature to determine if it meets the efficiency requirements outlined by ENERGY STAR.
Performance Requirements for Federal Purchases
Visit the ENERGY STAR website for the most up-to-date whole-home gas tankless water heater efficiency levels and product specification information, and a list of qualified water heaters.
Buying Energy-Efficient Gas Tankless Water Heaters
ENERGY STAR's Product Specification applies to whole-home, gas, tankless water heaters (also known as instantaneous water heaters) with nominal inputs from 50,000 to 200,000 British thermal units per hour (Btu/h), a minimum flow rate of 2.5 gallons per minute (rpm) with a 77°F temperature rise, and storage capacity of two gallons or less.
The Federal supply sources for gas water heaters are the General Services Administration (GSA) and the Defense Logistics Agency (DLA). GSA sells water heaters through its Multiple Awards Schedule program and online shopping network, GSA Advantage! DLA offers them through the Defense Supply Center Philadelphia and online through DOD EMALL. When purchasing gas tankless water heaters, specify or select models that are ENERGY STAR-qualified.
These requirements apply to all forms of procurement, including guide and project specifications; construction, renovation, repair, energy service, operation and maintenance (O&M) contracts; lease agreements; and solicitations for offers. Energy performance requirements should be included in all evaluations of solicitation responses. Buyers shall insert the standard clause from FAR section 52.223-15 into contracts and solicitations that deliver, acquire, furnish, or specify energy-consuming products for use in Federal facilities. Agencies can claim an exception to these requirements through a written finding that no ENERGY STAR-qualified or FEMP-designated product is life-cycle cost effective for a specific application.
Tankless water heaters (also called demand-type or instantaneous) heat water as it is needed. When an application (e.g., faucet, shower head, clothes washer) is turned on, the flow of water activates the burner. For some products, a minimum flow of one-half gallon per minute (rpm) is needed to activate the burner. If the water flow is below this level, hot water will not be provided. When installing tankless water heaters, make sure the minimum flow of each application is sufficient to activate the burner.
Ground water temperature will have an impact on the performance of tankless water heaters. A very low inlet temperature can reduce the amount of hot water delivered. Tankless water heaters are limited in the number of applications they can satisfy simultaneously. The largest tankless water heaters available provide around five gallons per minute (rpm). While this is enough hot water for several low-flow applications (e.g., bathroom faucets) or a couple moderate-flow applications (e.g., a shower and clothes washer), most tankless water heaters are unable to satisfy two high-flow applications (e.g., tub spigot, multi-head shower) at the same time.
The installation requirements for gas tankless water heaters are slightly different from storage type. The burners on gas tankless water heaters can have outputs as high as 200,000 Btu/h whereas the burners in storage type water heaters have outputs of 75,000 Btu/h or less. The supply line must be sized to provide enough gas for the larger burners. The venting requirements for gas tankless water heaters are different as well, especially for the most efficient products. Because of the low exhaust gas temperature and condensation that occurs as a result of efficiency improvements, corrosive-resistant materials are needed for the vent. The vents are typically run horizontally through walls instead of vertically through roofs and are limited to about 10 linear feet. Tankless water heaters must be connected to drain lines to dispose of the condensate.
Annual maintenance must be evaluated when considering tankless products, especially in areas with hard water. Consult with a reputable local installer who has experience with tankless water heaters to determine the proper unit, sizing, installation, and maintenance requirements for your particular situation.
Energy costs increase with temperature. Dishwashers require the hottest water of all household uses, typically 135°F to 140°F.Dishwashers, however, are usually equipped with booster heaters that raise the incoming water temperature by 15°F to 20°F. Setting the water heater between 120°F and 125°F and turning the dishwasher's booster on should provide sufficiently hot water while saving energy and reducing the chances for scalding.
Estimating Energy and Cost Savings
FEMP provides a cost calculator for water heaters that allows users to input different rates for natural gas, as well as values for energy factor and recovery efficiency. The output section displays results that reflect your energy usage and costs.
Finding More Information
Federal supply sources are the U.S. General Services Administration (GSA) and Defense Logistics Agency (DLA). GSA sells products through its Multiple Awards Schedules and GSA Advantage! DLA offers products through the Defense Supply Center Philadelphia and DOD EMALL.
Lawrence Berkeley National Laboratory provided supporting analysis for this acquisition guidance.