Introduction to DHW and Heat Pump Water Heaters
Domestic hot water (DHW) heaters provide hot water for a variety of uses including restrooms, dishwashing, and showers. Domestic hot water is typically heated in electric, natural gas, fuel oil, or propane-fired storage tank or instantaneous heaters and is stored at a temperature of around 130°F. Fossil-fueled DHW heaters typically operate with an efficiency ranging from 80 to 96%. Electric heat pump water heaters are up to 3 to 4 times more efficient than the standard electric water heaters.
How Heat Pump Water Heaters Work
Electric heat pump water heaters (HPWH) operate by transferring heat from the room air to an insulated water storage tank. The technology is very similar to a typical air conditioner except that it is rejecting heat to the water inside of a tank instead of outside. HPWH’s are more efficient than traditional water heaters because of their ability to use electricity to move heat from the surrounding air rather than generating it directly.
Average Lifespan: 8-20 years
Typical Payback Period: 5-10 Years
Eligible measure and technical standards:
| Heat pump water heater | ENERGY STAR, Energy Factor ≥3.0 |
| Indirect water heater – natural gas | Attached to ENERGY STAR boiler of ≥90% AFUE |
| Natural gas storage or condensing water heater | ENERGY STAR Certified, Thermal Efficiency (TE) ≥94% or Uniform Energy Factor (UEF) ≥0.86 |
| On-demand tankless water heater – natural gas |
ENERGY STAR, Energy Factor ≥0.94 with electronic ignition |
| On-demand tankless water heater – propane | ENERGY STAR, Energy Factor ≥0.82 |