What Are Heat Pump Water Heaters?

(aka Hybrid Water Heaters)

How do you heat your hot water? If you answered on your oil, natural gas or propane furnace or boiler, you might want to consider a heat pump water heater.

A heat pump water heater (HPWH) is also an electric water heater; it can run in heat pump only mode, electric only mode, or hybrid mode.

A HPWH, like a mini-split heat pump, uses a condenser and evaporator to pull heat out of the surrounding air and release it as heat. In the case of the HPWH, it releases the heat into the water in the tank. Unlike a mini-split, currently these units are not "split", which means that the HPWH is drawing the heat out of the air immediately surrounding it. Which means that if it is in your basement, it is pulling the heat out of your basement to heat your water. This means that the temperature will be a little chilly in your basement.

Additionally, Heat Pump Water Heaters need a certain amount of free air space around them. The general rule of thumb is 1,000 cubic feet (think a 10' high x 10 wide x 10' long space). HPWHs won't work well in a small closet.

Some HPWH's are a little tall, and some have their maintenance done by removing their cowling from the top rather than from the side, so it is important to know the height of the place where you want to put the water heater.

For brands, we like the GE GeoSpring, the AO Smith Vortex, and Rheem. The most common size is 50 gallon but larger families or hot water needs may want an 80 gallon water heater.

Important things to note on Heat Pump Water Heaters are 1st hour capacity, and energy efficiency ratio.


Compare to Other Ways to Heat Your Hot Water

indirect hot water heater

Heat pump water heaters vs. On demand propane or electric hot water heaters

Despite what propane dealers will tell you, do not think that you are going to save money by using an on-demand propane water heater. How do we know? Well, up front and personal, Ann Goggin had one and measured the quantity of propane, and then got a HPWH and measured the energy consumption of that. Rough estimate: she is saving over $500 PER YEAR using the heat pump water heater, vs. the on-demand Rinnai propane water heater. (This analysis was confirmed by her propane supplier and the company that sold her the on-demand Rinnai). That said, on-demand water heaters are very useful if you have a seasonal property and turn off the heat at times; that way you don't have to worry about water freezing in your tank. They are also practical if you have a large family and / or use a lot of hot water and don't want to run out of hot water. But don't get the on-demand heater to save money or energy.

Oil-fired water heater diagram

direct coil water heaters

Direct coil means that you do not have a tank attached to your boiler but rather run the boiler whenever you need hot water. This is the MOST costly set up, and nearly any other hot water heating strategy is better than this one. Maine has a large number of houses with direct coil water heating, and if we could wave a wand we could get all of these homes off this system. If you don't have a water tank, or an on-demand water heater (which we also don't recommend but some people are happy with theirs),  PLEASE investigate an electric or heat pump water heater right away.

gas fired hot water heater

indirect oil or gas fired hot water heaters

An indirect oil or gas fired hot water heater is one that use the fossil fuel combustion to heat the hot water, but doesn't require the entire boiler to start up just to heat the hot water.

These can be relatively efficient, especially some of the newer equipment, but you are still locked into burning a fossil fuel for hot water.


I would like to find out more about a heat pump water heater.

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