Heat Pump Water Heaters (HPWHs)
Heat Pump Water Heaters (HPWH) first appeared on the market in the 1970s. Other HPWH products re-appeared in the 1990s and 2000s, and there are currently several manufacturers. Current products are more robust with better controls than the earlier appliances. The largest market for HPWH is in warmer climates in the south, where the unit is located in the garage. The unit pulls heat from a warm garage to heat water. HPWHs have Coefficients of Performance (COP) of well over two, cutting electric energy use in half. Energy savings from a HPWH are often similar to that from a solar water heater.
Several hundred thousand rural and suburban homes in New York do not have natural gas available, and electric water heating is expensive (about $400 per year). In this case, an HPWH located in the basement of a single family home can reduce water heating costs by up to half. In a conventional, un-insulated basement, heat can be extracted without any significant impact on the space heating load of the conditioned space above. Summertime HPWH operation also reduces dehumidifier loads and energy use.
Our field test showed an annual conversion efficiency around 1.4. A large scale, NYSERDA-sponsored field test of 40 HPWH units lead by EPRI for the Delaware County Electric Cooperative (DCEC) has looked at both first- and second-generation HPWH products and found similar results (report expected in 2015). The newest generation of HPWH products offers larger tanks and better controls that promise to provide even better performance.
HPWHs might not make sense in a well-insulated basement where heat extracted from the basement has a direct impact on the space heating load. The Building America Measure Guide for HPWHs provides additional guidance about when HPWHs make sense and how to apply them.
Findings from our research project are also available here:
NYSERDA DHW Report