There are big developments happening in the world of water heaters. 120 volt heat pump water heaters are set to hit the market (most by early next year) allowing homeowners with gas water heaters to easily switch them out for heat pump water heaters without expensive panel upgrades. This opens up the world of efficient water heating to many more households, because they won’t have to rewire their homes to make the switch.
In previous, pre-climate catastrophe times, news about a new type of water heater might be laughable. Until relatively recently, no one thought much about the big tube-like machines with pipes and wires sticking out of them that sit in our closets, basements, or garages, which somehow provide all the steamy showers we could ever want.
However, how we heat water matters greatly in our efforts to decarbonize. Water heaters are the second biggest energy user in a typical household in the US, and a clean version of this boring technology might help save the day and our planet. With the right water heater we can have our cake and eat it too: we can have all the hot water we need and save money and not pollute.
Heat Pump Water Heaters Are Game-Changing
Image courtesy of New Buildings Institute
Heat pump water heaters are a rare example of a silver technological bullet. They clean up the way we heat our water, and reduce — and potentially eliminate — CO2 emissions from water heating. I’ve already written a full CleanTechnica article on the topic, in which I called them game-changing machines (this happened to be my best read CT article ever, and editor Zach Shahan laughed that an article on water heaters was the top read for the week). Heat pump water heaters are orders of magnitude more efficient than polluting natural gas and old electric resistance water heaters, which means families will save hundreds of dollars a year in energy costs and literal tons of CO2 emissions.
120 Volt Versions Make Gas Switch-Outs Easier
The lowest hanging fruit to more efficient water heating is to replace every inefficient, electric resistance water heater with a heat pump water heater. Both use 240 volts of electricity, so making the transition is relatively easy.
But what about the other 54% of water heaters across the nation, the 64 million (mostly natural gas-powered) machines that are heating the nation’s water?
The newest development in heat pump water heating is the production of a 120 volt version. Until now, heat pump water heaters have only been available with 240 volt electrical connections. 240 volts of electricity is needed to power both the efficient heat pumps (which sit on the top of the unit), as well as the electric resistance backup rods. These rods are the same technology used in standard electric water heaters and require a lot of electricity. Heat pump water heaters only use electric resistance backup when there is a lot of hot water demand and they can’t keep up, but this is rare.
The new 120 volt heat pump water heater gets rid of the electric resistance element. It only has a heat pump to heat your water, so it needs less electricity supply (but it still is able to provide all the hot water you’ll need — see below).
An estimated 50% of gas water heaters have an electrical line running to their ignitor switch to ignite their flames. Since they already have an existing supply of electricity, it’s easy to switch them out for the new 120 volt heat pump water heaters.
Before this 120 volt version of heat pump water heaters, it was necessary to up-size the wiring to a 240 volt wire to your electrical panel in order to swap from gas to heat pump water heaters. My family did this in our Accessory Dwelling Unit (apartment attached to our house). It’s doable, but adds additional work and expense. With this new version of the heat pump water heater, half the nation’s gas water heaters with a 120 volt electricity supply can easily be replaced with heat pump water heaters without running a new electrical line.
Can 120 Volt Heat Pump Water Heaters Still Heat All the Water I Need?
Image courtesy of New Buildings Institute
Even though they don’t have the electric resistance backup, 120 volt water heaters are still able to deliver all the hot water heater necessary, especially for households with 2-4 people in them.
In a recent webinar, Geoff Wickes from NEEA described how for every 10 degrees you turn up your water heater above the standard 120 degrees, it’s as if you get an extra 10 gallons of hot water storage. For example, in the winter I turn my family’s 50-gallon heat pump water heater from 120 to 140 degrees and this extra 20 degrees allows the water heater to act like a 70 gallon water heater because it has more hot water to mix with cold water. This strategy means you have to be more careful with the hotter water and have anti-scald devices on your faucets so the hotter water doesn’t hurt you or your kids.
120 volt heat pump water heaters come with an electronic mixing valve integrated into the water heater itself. This mixing valve allows owners to keep their water at a higher temperature and as the water leaves the tank, the valve will mix in “the exact amount of cold water needed to ensure the water comes out of the faucet at precisely the desired temperature selected by the homeowner.” (Source) Homeowners will thus get to store their water at a higher temperature and the water heater will make sure it’s still safe. This higher temperature will provide more hot water and thus the 120 volt water heater will be able to keep up with demand even though it has a slower recovery without the electric resistance backup.
Even though my family has a 240 volt heat pump water heater, we leave it exclusively in “Heat Pump Mode” so that we’re heating water more efficiently and never relying on the electric resistance backup. In essence, we’ve been living with a 120 volt heat pump water heater for four years now, and our first hand experience is that it recovers plenty fast and supplies all the hot water needed for a family of four plus an Airbnb rental.
When Can I Get My Heat Pump Water Heater?
These water heaters are just coming to market. I asked water heater expert Amruta Khanolkar, from New Buildings Institute, when they should be ready for purchase. She responded, “The Rheem models are market ready and the dedicated circuit one is available for sale already. The rest of the manufacturers and models are expected to be production ready by Q1 of 2022.”
The table below provides all brands available for both 240 volt and 120 with the 120 volt versions noted as “emerging.”
Image courtesy of New Buildings Institute
So start making a plan to switch out your gas hot water heater for a 120 volt heat pump water heater, especially if you’ve got a gas water heater with an electrical line. 120 volt heat pump water heaters open up efficient, electric water heating to millions of more homes, providing a major tool to individuals to reduce their emissions and fight climate change.
Huge thanks to Geoff Wickes and Amruta Khanolkar for sharing their expertise in this article. Check out a recent webinar I co-hosted for the nonprofit Electrify Now where both Jeff and Amruta presented on this game-changing technology. Amruta’s organization is part of the Advanced Water Heating Initiative, an initiative studying and promoting efficient water heating. To learn more, read here.
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