Heat pump water heaters promise higher efficiency and lower energy costs than standard resistance-type electric water heaters, and a lower carbon footprint than water heaters that rely on natural gas. But as Ted Cushman notes in his 2017 JLC article Heat Pump Water Heaters, they have some limitations too. Heat pump water heaters (HPWH) work by pulling heat out of the room air where they’re located, so they need at least 800 cubic feet of space around them—and when they’re operating, they can cool that surrounding space by as much as 5°F to 10°F. The heat-pump motors aren't as quiet as other types of water heaters either, and it takes them longer to bring cold water up to their set temperature.
As part of a major overhaul of his own home's mechanical systems, Allison Bailes of Energy Vanguard replaced his gas hot water heater with a Rheem HPHW in 2019, and has been monitoring its performance ever since. In this recent article, he reports on its actual energy consumption and makes general observations about how the unit has (or hasn't) met his expectations.
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