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Heat Pump Water Heater Basics

Heat pump water heaters are a relatively new technology. Most units extract heat from the surrounding air and use it to heat water in a storage tank that is often taller than a conventional storage tank. In some cases, heat can be pulled from the ground (ground source or geothermal heat pumps) to heat a home’s space and then an additional unit called a desuperheater uses gases from the heat pump’s compressor to heat water for domestic uses.

In theory, ‘air source’ heat pump water heaters can have Energy Factors between 2.0 and 2.5, but in practice this can vary widely based on climate, the conditions of the room in which the unit is installed, and other factors. A caution in regards to air source heat pump water heaters is that pulling heat from the air of the surrounding room will cool the space. Because Colorado homes have more heating needs than cooling needs, this can add to the energy needed for space heating which offsets some of the benefit of the heat pump water heater. And because heat pump water heaters require backup electric resistance heat when the surrounding air is less than 40 degrees F, they will not function efficiently in rooms that tend to be cold. These units are more expensive to purchase than electric storage water heating units but save money in operating costs.

Heat pump water heaters with tanks are sized in the same way other storage hot water heaters are sized. Consult with a contractor if you are interested in integrating water heating to a heat pump that currently provides only space heat. Because the technology is relatively new, little is definitively known about the lifetime of these units.