Ariston ARIHPWH-80

It holds 73 gallons in the test, 7 gallons less than its 80-gallon sold size. It delivers 87 gallons of hot water in the test's first hour. Its tank holds 73 gallons, so reheating adds 14 gallons during the first hour. Among 481 heat pump models, 71 have a higher first-hour rating. The median heat pump model gives 72 gallons in the first hour of the test.

It is ENERGY STAR certified under its single model number. In the test, it gives 4.01 units of hot water energy per unit it uses (its UEF). A UEF above 1 is possible because it moves heat from the air into the water. Its test ran at the high level of daily hot water use. Of 237 heat pump models with the same draw pattern, 68 have a higher UEF and 167 a lower one. For its type and draw pattern, the UEF runs from 2.85 to 4.95. While it reheats, the water gains 443% of the energy it uses (its recovery efficiency).

All of its test figures are shared by one other basic model. That one is listed under the AMERICAN STANDARD WATER HEATERS brand. For the full group, see the AMERICAN STANDARD WATER HEATERS ARIHPWH-80.

It may qualify for 20 rebate programs. Another 7 rebate programs may accept it if it meets their other terms.