Ariston ARIHPWH-50

It holds 45 gallons in the test, 5 gallons less than its 50-gallon sold size. Starting full, it gives 68 gallons of hot water in its first hour of use. Its tank holds 45 gallons, so reheating adds 23 gallons during the first hour. In the first hour, 285 of the 481 heat pump models give more hot water. Among heat pump models, the median first-hour rating is 72 gallons.

Its single model number, ARIHPWH-50, is ENERGY STAR certified. In the test, it delivered 3.75 units of hot water energy for each unit used (its UEF). It moves heat from the air rather than making it, so its UEF passes 1. The daily hot water use in the test, called its draw pattern, was medium. Among 226 heat pump models on its draw pattern, 59 have a higher UEF. A UEF of 3.68 is the median for its type and draw pattern. While it reheats, the water gains 430% of the energy it uses (its recovery efficiency).

Its test figures match those of one other basic model. That one is listed under the AMERICAN STANDARD WATER HEATERS brand. You can find the whole group on the page for the AMERICAN STANDARD WATER HEATERS ARIHPWH-50.

In 20 states, 21 rebate programs may accept it. Another 7 rebate programs may accept it if it meets their other terms.