Getting Into Hot Water — Part 4

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Monitoring data show that the Geyser heat-pump water heater didn't save very much electricity, while a Stiebel Eltron unit performed better

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I've now had a year with the Geyser heat-pump water heaterAn appliance that uses an air-source heat pump to heat domestic hot water. Most heat-pump water heaters include an insulated tank equipped with an electric resistance element to provide backup heat whenever hot water demand exceeds the capacity of the heat pump. Since heat-pump water heaters extract heat from the air, they lower the temperature and humidity of the room in which they are installed. (HPWH). With the exception of the puddle on the floor in July 2011, it has performed consistently.

Its performance has not been thrilling, though. In the summer, it was making hot water at about 0.13 - 0.15 kWh/gallon, with incoming water in the mid-60°Fs and basement air temperature around 70°F. In the winter, with basement temperatures in the low to mid 50°Fs, and incoming water at 50°F or a bit below, this consumption ratio increased to 0.25 kWh/gallon.

URL: http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/getting-hot-water-part-4