You are here

Covered Product Category: Residential Heat Pump Water Heaters

The Federal Energy Management Program (FEMP) provides acquisition guidance and Federal efficiency requirements for residential heat pump 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.

The following guidance and requirements apply to residential heat pump water heaters that operate on 250 volts or less, have a current rating of 25 amps or less, and a first hour rating (FHR) of 50 gallons or greater. Residential electric water heaters are covered by a separate specification.

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 below. Visit the ENERGY STAR website for a list of qualified water heaters.

Energy Efficiency Requirements

Energy efficiency requirements for various residential heat pump water heater types and sizes are outlined in the following chart. Federal purchases must meet or exceed these requirements.

Energy Efficiency Requirements for Federal Purchasesa
Fuel and Type Energy Factorb Annual Energy Usec
Electric heat pump 2.0 or greater 2,195 kWh or less

a Requirements as of August 3, 2011. For the latest efficiency requirements, visit
b Energy factor is an efficiency ratio of the energy supplied in heated water divided by the energy input to the water heater.
c Based on U.S. Department of Energy (DOE) test procedure (10 CFR 430, Subpart B, Appendix E).


Specify or select residential heat pump water heater models that are ENERGY STAR-qualified, all of which meet the performance requirements outlined above. To verify products meet this energy efficiency requirement, look for the ENERGY STAR label or check the annual energy use (kWh/year) listed on the yellow EnergyGuide label required on these products.

Technology Deployment

FEMP identifies heat pump water heaters as a new and underutilized technology. Federal laws and regulations mandate aggressive agency energy use reduction goals that can be difficult to reach with conventional technologies. Agencies should consider new and underutilized technologies where appropriate to help meet these goals while accelerating Federal adoption. This energy efficiency requirement contains information to assist agencies with properly selecting, installing, and operating residential heat pump water heaters.

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.

Buyer Tips: How to Choose Efficient Products

Heat pump technology has been used for many years for space heating and cooling. It can be found in small and large products alike, such as window air conditioners used in homes through large rooftop units used in commercial buildings. Starting in 2010, several major manufacturers incorporated this technology into residential electric water heaters and introduced these products to the market. Heat pump water heaters are now the most efficient electric models available, using half the energy or less than standard electric models. Heat pump water heaters are the same size and use the same connections as standard models, so they offer a drop-in replacement for most electric water heaters.

Federal agencies should consider heat pump water heaters over all other types due to their high efficiency. However, to function properly and achieve this higher efficiency, heat pump water heaters must be installed in spaces that meet the following requirements:

  • Air Volume: Heat pump water heaters need a heat source of 500 to 1,000 cubic feet of air volume. Unconditioned spaces, such as basements and garages, are preferred. Exhaust air is cooler and drier than intake air, which is a benefit in hot/humid locations as heat pump water heaters can cool and dehumidify the air. This, however, could be a problem in cold climates.

  • Clearance: Heat pump water heaters draw ambient air into their refrigeration systems, extract heat, and then exhaust the cooler air. Obstructions to this airflow, such as being too close to a wall or low ceiling, negatively impacts this heat transfer and lowers unit efficiency. Each manufacturer has a different recommended location for the air intake and exhaust. Buyers must select the heat pump water heater that works best in their specific location.

  • Air Temperature: Heat pumps are designed to operate in ambient air temperatures between 40°F and 120°F. When the temperature is outside this range, the water heater operates in electric resistance mode, which lowers its efficiency. Avoid installing heat pump water heaters in locations with ambient air temperatures outside this range for extended periods of time.

  • Drain: Like other refrigeration technologies, heat pumps generate condensation that must be drained. The installation space must have access to a drain line. If a drain line is not close by, a pump can be installed with condensate removal.

Consider using a high-efficiency, electric resistance, storage-type water heater if conditions do not meet the installation requirements discussed above or the manufacturer requirements for heat pump water heaters.

Water heaters must be sized properly. Oversized products cost more to buy and use more energy due to excessive cycling and higher standby power losses. A water heater should be selected based on its FHR, not storage capacity. The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) offers a worksheet for estimating FHR.

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 ENERGY STAR-qualified and 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 below cost effectiveness example or the water heater energy and cost calculator.

Products meeting FEMP-designated efficiency requirements or ENERGY STAR performance specifications may not be life-cycle cost effective in certain low-use applications, such as when a device is being purchased for backup purposes and will remain in off mode for most of its useful life. For most other average or high-use applications, purchasers will find that energy-efficient products have the lowest life-cycle cost.

The table below provides energy and cost savings for heat pump water heaters. The efficiency of the base model is the minimum allowed by DOE appliance standards for an electric resistance, storage-type water heater with a 50-gallon capacity and FHR of 67 gallons. The required model is an ENERGY STAR-qualified heat pump water heater with a 50-gallon capacity and FHR of 67 gallons. The best available model is the most efficient model ENERGY STAR-qualified heat pump water heater available with a 50-gallon capacity and FHR of 63 gallons.

Energy and Cost Savings Example
Performance Base Required Best Available
Energy Factor 0.90 2.00 2.35
Annual Energy Use 4,879 kWh 2,195 kWh 1,856 kWh
Annual Energy Cost $440 $198 $168
Lifetime Energy Cost $4,510 $2,035 $1,720
Lifetime Energy Cost Savings $2,485 $2,800


In the example above, the required model is cost effective if priced no more than $2,485 above the base model. The best available model is cost effective if priced no more than $2,800 above the base model.

Annual energy use is based on DOE test procedure (10 CFR 430). The assumed rate of electricity is $0.09 per kWh, the average at U.S. Federal facilities. Lifetime energy cost is the sum of the discounted valued of annual energy cost with an assumed water heater life of 13 years. Future electricity price trends and a 3% discount rate are from the Price Indices and Discount Factors for Life-Cycle Cost Analysis.

User Tips: How to Use Products More Efficiently

Heat pump water heaters have advanced controls and interface modules that allow users to easily turn the unit on and off, switch modes, and change temperatures. When used properly, these features can deliver additional savings. Below are brief descriptions of the different operating modes:

  • Efficiency: Only the heat pump operates regardless of demand for hot water. The electric resistance elements are not used except when the air temperature is too cold (45ºF or less) or too hot (110ºF or greater). The energy factor will be 2.30 or higher, and energy use will be the lowest. Note that there may be periods when hot water demand is not met. Without the use of electric resistance elements, recovery times will be longer and FHRs lower. In smaller households or households that spread hot water use throughout the day, this mode will provide sufficient amounts of hot water in the most efficient manner.

  • Electric Resistance: The heat pump is shut off and the unit functions like a conventional water heater by using only the electric resistance elements. The energy factor in this mode will be around 0.90, so it should be used sparingly. To limit time spent in this mode, some products automatically reset to previous settings within a week or two. This mode is useful during the winter if the exhaust air makes the space too cold.

  • Hybrid: A combination of efficiency and electric resistance modes. The general concept is to maximize heat pump use and minimize electric resistance element use to match the hot water output of standard electric water heaters. Hybrid mode, which has an energy factor of 2.0 or greater, is the default setting for most heat pump water heaters and should meet hot water demand while using substantially less energy than standard electric water heaters.

  • High Demand: For higher than average usage (e.g., when hosting out of town guest). The electric resistance elements are used more so the heat pump water heater can recover more quickly. More energy is used to satisfy the higher demand for hot water. Not all products have this mode.

  • Vacation: Used during periods of extended absences when the water heater sits idle. The water temperature is allowed to drop well below the set point to minimize standby losses. Any standby losses are made up with the heat pump so energy use is minimized. Typically, the user inputs the number of days away. Approximately 12 hours before this period ends, the heat pump water heater is reset to its previous mode to heat the water prior to user return.

Set heat pump water heaters to the mode that best meets hot water demand, which is typically efficiency or hybrid. Other modes, like vacation or high demand, are very useful in specific situations. Due to its low efficiency and high operating cost, electric resistance mode should only be used when necessary.

Vapors from gasoline, paint thinner, and some other products are extremely flammable and can easily ignite. Do not use or store any flammable liquids or highly combustible materials near heat pump water heaters. The electrical contacts used in heat pump water heaters can ignite vapors and cause explosions or fires that result in property damage, injury, or death. In addition, vapors from products like bleach, fabric softeners, and detergents can be corrosive and damage heat pump water heaters. Do not use or store any corrosive products near heat pump water heaters. This could be problematic when water heaters are located in utility rooms that also contain clothes washers and dryers.

Unlike standard products, heat pump water heaters have a filter that must be cleaned regularly. Some models have an alarm that lets the owner know when to perform this maintenance. Check the owner's manual for more information on when and how to clean the filter.

For most residential applications, set the temperature at 120ºF. Under certain conditions, Legionella pneumophila, the bacteria known to cause Legionnaires Disease, can grow in water heaters. The Unified Facilities Criteria (UFC), the master specification used by the U.S. Department of Defense (DOD), requires users to "set service water heater (SWH) storage temperature set point for not less than 140ºF (60ºC) to limit the potential for growth of Legionella pneumophila." At this water temperature, bacteria can survive for less than a minute. Water temperature this high poses a risk of scalding, especially for young children and the elderly. Because of this, the UFC requires a "balanced-pressure-type tempering valve" to be installed downstream of the service water heater storage tank to provide anti-scalding protection. For residential applications, set the temperature on this device, also known as a mixing valve, to 120°F.

Do not wrap heat pump water heaters with insulation blankets. These products are well insulated and the blankets could impede airflow into or out of the units, which reduces efficiency and could void the warranty.

Federal Supply Sources

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.