The 120-volt plug-in heat pump water heater is here! The effort to bring these things to market began in 2018, and now they’re available to buy. This technology has some significant advantages over the standard 240-volt heat pump water heater. But it also has a drawback. Let’s take a quick look.
The big 120 V plug-in advantage
The 120-volt plug-in heat pump water heater requires, well, half the voltage of the standard models, like the one I have in my basement. Any electrical device that uses 120 volts can be plugged into a standard outlet whereas 240 volt devices need special wiring and connections. You can plug in a 240 volt appliance to an outlet with a special plug and outlet. Think electric clothes dryers. Most 240 V appliances, however, are hard-wired.
The thing about 240 volt appliances, though, is that you need more than just a different kind of outlet and plug. You may need three changes to make a 240 V heat pump water heater work in your home. First, a 240 V appliance probably needs two breaker slots in your electrical panel. That could mean you need a bigger panel or to have an electrician rewire things within.
Second, it also uses more electricity. That could mean having to upgrade the electrical service to your house. If you’ve got, say, a 100 amp (A) service, you may need to upgrade to a 150 A service to install a 240 V heat pump water heater. (See my second article on electrification, though, to find out more about panel upgrades.)
Third, you’re going to have run a new circuit from the panel to the 240 V heat pump water heater. This will require paying an electrician to open the panel, run the wiring to the water heater location, and set up the connection. When I electrified my 1961 home in 2019, I replaced the old fossil gas water heater with a 240 V heat pump water heater. The electrician charged me $600 to install the 240 V circuit.
So the big advantage of these new 120 V plug-in models is that they can save you thousands of dollars avoiding changes to the electrical system in your home.
The 120 V plug-in drawback
As you might expect, the lower voltage delivered to the plug-in heat pump water heater means less ability to heat water. That’s because it also gets less electrical power. The 240 V models are called hybrid heat pump water heaters because they have three ways of heating water.
They can use the heat pump. They can use electric resistance heating elements, the same kind you’d find in a standard electric water heater. Or they can use both the heat pump and the electric resistance.
With the 120 V plug-in models, you don’t get the big electric resistance heating elements that come with the 240 V models. Some don’t have the backup heating element at all. That’s great for efficiency, but it may limit your hot water.
I say “may limit your hot water” because the real difference between 120 V and 240 V heat pump water heaters is how much backup heat is installed. I have a 240 V model and keep it in heat-pump-only mode unless we have extra people staying with us and need faster water heating. That’s happened only once in four years though, but we do have the 80 gallon model.
Is a plug-in heat pump water heater right for you?
Heat pump water heaters use only a few hundred watts of power when they’re using only the heat pump. The highest I’ve seen mine go since I started monitoring my electricity last year is a bit above 400 W. Since I almost never turn on the electric resistance heat, I could have gone with an equivalent 120 V model.
What it comes down to is how much hot water your heat pump water heater can make and how much hot water you use. Well, I guess another factor would be how afraid you are of running out of hot water. We’ve had that problem only once with guests in the house.
If you have the electrical capacity already or are building new, you should be able to do it without adding much cost. In an older house that would require significant changes to your electrical system, the 120 V plug-in model can save you thousands of dollars.
Two ways to make 120 V plug-in heat pump water heaters go further is to get one with a larger tank or make the water hotter and then use a mixing valve to drop the temperature before use.
Heat pump water heater resources
There’s a lot of really good information available about both kinds of heat pump water heaters. See the related articles below for what I’ve written on this topic. Here are some other good resources:
- Canary Media published an article about the new plug-in models.
- The Advanced Water Heating Initiative (AWHI) has a lot of great info.
- The New Buildings Institute published an article about a 120 V plug-in heat pump water heater study and the report on that study. The study is title, Plug-In Heat Pump Water Heater Field Study Findings & Market Commercialization Recommendations and is available as a free download.
Today is Heat Pump Water Heater Day!
Finally, whether you’re interested in the new 120 V plug-in heat pump water heater or the standard 240 V models, you can celebrate Heat Pump Water Heater Day. So post a photo online of you hugging your heat pump water heater if you have one. Here’s mine:
The event is hosted by the Advanced Water Heating Initiative and there’s a full agenda for the day on their site, including webinars, resource drops, and more. Check it out!
Allison A. Bailes III, PhD is a speaker, writer, building science consultant, and the founder of Energy Vanguard in Decatur, Georgia. He has a doctorate in physics and is the author of a bestselling book on building science. He also writes the Energy Vanguard Blog. For more updates, you can subscribe to Energy Vanguard’s weekly newsletter and follow him on LinkedIn.
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