Last fall I wrote about how 120 volt heat pump water heaters were just about to come out on the market. Well, they’re finally here! Rheem released its 120V ProTerra(R) Plug-in Heat Pump water heater (HPWH) in July and everyone is excited!
Ok, you may not geek out on heat pump water heaters as much as I do, but these bad boys are the unsung heroes of the climate movement with massive potential to save money and the planet at the same time. HPWH are the energy equivalent of 7 solar panels that cost ⅙ of the price. They use a quarter of the energy of a standard electric resistance or gas water heater.
What’s not to love?
Well, up to now, one potential challenge was installation. If you had a gas water heater and wanted to replace one with a HPWH (which you should do to decarbonize ASAP) you often had to run a new 240V electric line from your electrical panel to your water heater to have enough energy to power the heat pump water heater.
240 volts are required because even though the water heater sips energy with a heat pump most of the time, it’s equipped with high powered electric resistance rods that can kick in during rare periods of really high demand and those rods require a lot of juice. But the times you need those electric resistance elements are pretty rare. In my house for example, we run our HPWH exclusively on heat pump mode all year long and never use the backup electric resistance rods and never run out of hot water even with 3 showers.
120 Volt Plug-ins Hit The Scene
In 2019, the nonprofit-led Advanced Water Heating Initiative (shameless plug, pun intended, I work on this initiative) saw the need for a water heater that could be plugged into a typical outlet and avoid the electric panel upgrades to help people easily switch from gas to electric water heaters. Lots of organizations, from utilities to nonprofits (huge shoutout to Building Decarbonization Coalition) to manufacturers, began meeting regularly to dream and design this 120V HPWH into existence. Manufacturers then built demo products that are currently being tested in New Buildings Institute’s California field study.
Rheem became the first manufacturer to bring a product to market with its 120V ProTerra Plug-in that comes in two models — a dedicated circuit model (where the water heater is the only thing plugged into that circuit) and a shared circuit one.
How A Water Heater Can Work On 120 Volts
A couple of tricks can help heat pump water heaters work with just 120V. First off, heat pumps on their own produce about 10-15 gallons of hot water an hour. With a tank that stores about a day’s worth (60 gallons) of hot water, most families usually have plenty of hot water. This is why my home never runs out of hot water with a heat pump even with three showers.
Second, Rheem has added an integrated mixing valve into its 120V water heater. That means the ProTerra Plug-in water heater can store water at hotter temperatures (like 140 degrees instead of 120 degrees). The mixing valve then mixes cold water into the 140 degree water so it doesn’t scald you when coming out of the faucet. Setting a water heater at 140 degrees over the standard 120 degrees provides a up to a 34% increase in hot water available, so a 60 gallon water heater at 140 degrees will be equivalent to an 80 gallon water heater at 120 degrees.
A 120V HPWH Might Not Be For Everyone
There are a couple things to think about when deciding if a 120V Plug-in HPWH might be for you. First off, if you’re one of the 50% of American homes that has an electric resistance water heater, you don’t need to get a 120V plug-in heat pump water heater. Your electric resistance water heater is already running on 240V of electricity, so you could install a 240V HPWH (and probably should) because it’s nice to have that electric resistance backup.
Also, check to see what other plug loads would share the circuit with the water heater. If it’s another device with a big load like a furnace or vacuum, you could potentially cause your breaker to trip frequently when running the heat pump water heater, which would be annoying. If you have a dedicated circuit near your gas water heater, you could go for Rheem’s dedicated circuit 120V Plug-in HPWH which has a bigger compressor and heats water even faster. If your home was built after 2002 in CA, you probably already have this dedicated circuit.
The 120V ProTerra Plug-in water heaters are also designed for warmer climates. Rheem isn’t going to market or stock them in colder states. The reason for this is that the recovery rate will be slower with the colder ambient air temperatures in the Northeast and Midwest. I personally think these 120V models will work fine in the NE. We run a 240V HPWH in heat pump mode all year long in the basement of a rental property in Cleveland, OH, and have never had a complaint.
Several manufacturers are likely to come out with cold weather 120V HPWH versions in the next couple of years though, so you could also just wait for that one.
If you’re interested in buying the Rheem Plug-in ProTerra in CA or elsewhere, you have a couple options, but unfortunately, it isn’t too easy to get your hands on one just yet. Here are some suggestions; Either consult with your local plumbing contractor (https://www.rheem.com/find-a-pro) and see if they can order one through a national distributor with whom Rheem partners or go to the Prodesk of a Home Depot and have it special ordered — just make sure you have the model number (which you can find here). Unfortunately, you can’t order directly online at Home Depot yet, but if enough of us start demanding them, we might be able to change that.
Even if the 120V HPWH isn’t an option or available for everyone just yet, the arrival of the first Rheem 120V model is exciting. It offers more households an opportunity to move to vastly more efficient water heating and save money and energy and reduce emissions. With the Inflation Reduction Act’s rebates for heat pump water heaters, the upfront costs should also come down as well, putting advanced, 21st century water heating within reach for many more Americans.
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