24 June 2014
Heat pump water heaters (HPWHs) extract thermal energy from their
surroundings to make hot water with two to three times better efficiency than conventional electric resistance water heaters. But, how much does HPWH placement influence its
performance? This paper summarizes performance metrics of two 189 L (50 gallon) HPWHs– one placed within conditioned space, and the other placed in the garage of two separate,
but similar research houses – each delivering approximately 208 L/d (55 gallons/d) hot water under simulated occupancy conditions. Both houses had space conditioning set points of
24.4°C (76°F) and 21.7°C (71°F) in Summer and in Winter, respectively, and hot water temperature setting of 48.9°C (120°F). Performance metrics are compared on a monthly
basis for 2011. Performance is also compared to that of three HPWHs installed in occupied homes.