Heat Pump Water Heater

This Evolving Technology Moves Into The Mainstream

Understanding if it’s right for your situation is the key – it’s not for everyone.

An evolving water-heater technology has been moving more mainstream over the past couple of years. This technology uses a heat pump (think air-conditioner or refrigerator working in reverse), to heat the water.

A Heat Pump Water Heater (HPWH) almost sounds too good to be true since it can be one and a half times as efficient as a standard electric resistance water heater. Certainly that increased efficiency can add up to big savings over time and for that reason it can be a great choice for many homeowners.

It’s not for everyone, however. In most cases, if you heat your water with natural gas it won’t make sense to switch to a HPWH. Many factors go into whether or not switching to a HWHP makes sense including gas and electric utility rates, usage patterns, and certainly climate.

These water heaters are often 50-gal tank size, but don’t always provide the capacity or the efficiency benefits for high-usage situations. A heat pump takes longer to make the water hot, so although they are efficient, they might not always be convenient. To compensate there is a standard heating element that you can use to speed things up in “high demand” situations. In fact, you can set it to standard mode and it will function just like a regular electric hot water heater, and cost the same to run.

Because of the compressor and fan, a HPWH does make some noise while it’s running—about the same as a full-size microwave. Given that water heaters are often in basements, garages, or otherwise isolated from the living space, this may not be an issue. The compressor on top makes the unit taller than a similar sized electric hot water heater so it won’t fit in some shorter spaces.

Here’s what is “cool” about HPWH’s. A heat pump pulls heat from the air and transfers it to the water using a compressor. It’s sort of like an inside out refrigerator cooling the air around it, not the stuff in it. This certainly is an added benefit in cooling climates and for sure there is some dehumidification in the process too. However, in heating climates where you’re paying to heat your home for much of the year and the water heater is often in the same space as the boiler or furnace, a HPWH only generates significant savings during the summer months when you’re not heating the home. The rest of the year it is stealing heat from the losses of the heating system in the same space cooling that very space you are inadvertently heating.

In the north the groundwater temperatures are also much colder which means more heat is needed to raise the water to temperature, and the current models may struggle with this. With the “hybrid” systems, this means that the electric resistance heating element will be kicking in, reducing your savings.

Bottom line: A HPWH can be a good choice in cooling climates in areas where you heat your water with electricity—especially where electric rates are high. But it wouldn’t be the best choice if you already heat with gas or live in a cold climate.