This post is about water heaters, but I didn’t think a photo of a water heater would garner much attention, so I opted for the pretty-woman-in-the-shower picture. The news here is important, though, and worth attracting some attention—in the last few years heat pump technology has made two areas of household energy use dramatically more efficient. One of those areas is space heating, with the advent of affordable and highly efficient cold-climate heat pumps (also known as “ductless mini-splits”), and the other area is water heating. Heat-pump water heaters are now available that are two to three times more efficient than standard resistance-element heaters, and could save the average family $300 a year or more. As one would expect, they’re more expensive than standard models, but heating water is one of the larger energy demands in most houses, and because of this the units can pay for themselves in just just a few years. And after they’ve paid for themselves, it’s money in your pocket every month, and far better for the planet, too. Like I’ve said before, efficiency really is the goose that lays the golden egg.
There’s a short video on this Consumer Reports page that gives a good overview of these heaters. Basically, the units use heat pumps, similar to those in refrigerators or air conditioners, to pull heat from the air and put it into the water, and this takes only about a third as much energy to accomplish as creating that heat with a resistance element. Now, while these heaters are probably a wise investment for the vast majority of homeowners, there are a few factors to be aware of before deciding to make a switch. Among them:
— The heaters produce dehumidified air as they operate, which is a side benefit for most people. But, unlike a standard water heater, they need to be installed where there is access to a drain for the condensate to drip into.
— The units are a bit taller than standard water heaters, because the heat pump portion typically sits on top of the tank, so you need to have space for that. Here’s a picture of the Whirlpool model I bought as part of my current net-zero project, and you can see how it’s taller–
— Because heat pump water heaters pull heat from the surrounding air, they operate more efficiently if they have a bit of extra space around them. In most installations this isn’t a problem, but if your current water heater is in a very tiny closet, it might be an issue. Related to this, they cool the air around them as they operate. If you live in hot climates, then this can be another benefit. In colder climates, you might see less overall efficiency gains in the winter if the building has inefficient space heating, and the water heater forces that system to work harder.
— Because the price of solar PV panels has come down so dramatically, it is now cheaper to heat water with a heat-pump water heater and electricity from PV, than it is to install a thermal solar water heating system. This path to hot water requires far less maintenance, too.
— The units do make some noise, unlike standard electric water heaters. I don’t have mine installed yet, but the water heater we’re replacing is a direct-vent propane model, which has a blower fan, and I actually expect the new one to be quieter.
So, these heat-pump water heaters might not work for everyone, in every situation. If I had to generalize, though, I’d say that the vast majority of everyone out there with a standard resistance-style electric water heater could come out way ahead by switching to a heat pump model. For those people who get hot water from a fuel-oil furnace, it might enable them to turn off their furnace in the summer, when they might otherwise have to keep it running. And for people who heat water with natural gas, the units might not save enough to pay for themselves. Though, if you could switch from natural gas to heating with renewable electricity, then it would still be a big win for the planet, even if your pocketbook didn’t see a difference.
I know two people right now who have switched, and both seem to be thrilled with the performance of their new models. I’ll have ours in soon, and I’ll do a post about it in a month or so.