The 120-volt plug-in heat pump water heater allows homeowners to easily plug a highly efficient water heater into a standard outlet. This is transformational because it allows the 60 million U.S. homes with gas water heaters to easily and cheaply transition to a clean, efficient, cost saving heat pump option. We are among the first households in the country to buy and install one at a family home in Cleveland, Ohio, so we can now sing the praises of this innovative technology.
How A 120-Volt HPWH Works, & Why It Matters
Heating water is the second biggest energy use in the home (after space heating) but few of us think of our water heaters as a major opportunity to save money and help the environment. Water heating costs homeowners hundreds of dollars annually, and fossil fueled water heaters emit a lot of carbon dioxide.
The heat pump water heater solves these water heating woes. It’s incredibly efficient, typically costs around $100/year to operate, and reduces carbon emission by about 1 ton per year compared to fossil fuel water heaters. But until last year, all heat pump water heaters operated on 240-volts of electricity, essential to power their backup electric heating elements which kick on during rare periods of high demand (see image below).
240 volts of electricity is problematic for the half of homes in the U.S. that have gas water heaters. These homes often don’t have electricity nearby, so converting from a gas water heater to a heat pump requires a new 240-volt electrical wire. This is doable (our family has done it three times) but often requires an electrician, new circuit breakers, and sometimes a panel or even electrical service upsize. All this adds cost and complexity and makes it hard for people with gas water heaters to switch to heat pumps, especially if they’re in the most common replacement scenarios where a broken water heater needs to be fixed that day.
Enter the game-changing 120-volt plug-in heat pump water heater. Back in 2018, a number of organizations recognized the gas to heat pump conversion challenge and came together to develop a water heater that plugs into a standard outlet. In 2022, their work paid off as Rheem released the first model, and A. O. Smith just followed this year.
How Does a Water Heater Get All the Energy it Needs from a Standard 120-Volt Outlet?
- Heat pumps work wonders on very little energy. Heat pumps move heat with electricity and refrigerants instead of creating it. This is extremely efficient and thus requires very little energy (350-450 watts). 120-volt models (for the most part) only rely on heat pumps, eliminating the backup electric resistance heating elements by using the two strategies below.
- Water heaters store a lot of energy in their tanks. An average household uses 64 gallons of hot water per day. With a 65 or 80 gallon tank, there is plenty of hot water stored for a typical household even if it reheats more slowly. A common strategy with the 120-volt HPWH is to install a larger tank with more hot water storage. The early rule of thumb some installers are using is to go up two sizes from a gas model, so if you have a 40-gallon gas tank, install a 65-gallon heat pump water heater tank.
- 120-volt HPWHs have integrated mixing valves that allow water to store at higher temps. Heating water to 140 degrees instead of 120 creates approximately 32% more hot water. A mixing valve combines cold with hot water to avoid scalding, and the 120-volt heat pump water heater comes with one already installed on the tank. Thus, it’s easy to keep the water at a higher temperature on a 120-volt heat pump water heater, which results in more hot water.
These factors allow the 120-volt heat pump water heater to eliminate the electric heating elements and rely exclusively on the heat pump.
Our 120-Volt Experience
As heat pump water heater aficionados, we were excited to test the 120-volt option at a family duplex in Cleveland. On the south side of the duplex, we had already switched out the gas water heater for a 240-volt heat pump in 2021. We’ve run it in “heat pump mode” only (meaning the backup electric heating elements never kick in), which gave us confidence in the 120-volt plug-in.
On the north side, we opted for the new 120-volt technology to replace the gas water heater, which at 30 years old was at the end of its life. We highly recommend proactive replacements! We liked the plug-in because we avoided running a new 240-volt line from our small circuit breaker. After four months of stellar performance, we’re happy to share what it took to purchase and install this cutting edge product.
Step 1: Order the Water Heater. This was the hardest part of the process. Back in July, you couldn’t buy the water heater online (now it is available!) so we had to call Home Depot with the Rheem model number in hand and place a special order. It took seven days, and a couple 30-minute phone calls, to explain what we wanted to the kind Home Depot folks who placed a special order with suppliers. A week after placing the order, we received a call from Home Depot saying that Rheem recommended we not buy the water heater because it wasn’t designed for the Cleveland climate. With Joe being steeped in the latest research from his work on the Advanced Water Heating Initiative, we were confident in the technology’s ability to store plenty of water and recover on a heat pump mode, especially given our six years of experience running our home water heater in heat pump mode. We finally received the order 32 days after the initial phone call. This ordering process was pretty challenging, and we’re glad it’s now possible to order one online.
Step 2: Find a Plumber. Next we had to find a Cleveland area plumber to install it. Heat pump water heaters are still unfamiliar technology to many plumbers and contractors nationally. We identified a local company, Dunrite Plumbing, which was available and willing to do the work but had never heard of our favorite climate saving technology. We let them know that it was just like installing an electric water heater but without having to do any wiring because it plugs into a standard outlet. It also requires a condensate tube to drain water, but there was a drain nearby, which made this easy. Dunrite was a bit apprehensive, but agreed to show up on the designated day.
Step 3: Prepare for Installation. We had to pick up the water heater at Home Depot and make sure there was an outlet within 10 feet of its new home. We didn’t have a plug that close, but a recent kitchen remodel conveniently left a spare electrical wire to which we wired a 120-volt receptacle. We tested the circuit to confirm there weren’t any other large electrical loads on it.
Step 4: Install Water Heater. The installation was the easiest part, proving why so many are excited about this product. Even though it was a new technology for Dunrite, they removed the gas water heater and installed the new 120-volt heat pump water heater in just two and a half hours. This matches the time it usually takes to replace a standard gas water heater. The only difference was that the plumber had to cap the gas line, move the hot and cold water connections from the top of the old water heater to the sides of the new one, and add a condensate tube that emptied into a nearby floor drain.
Step 5: Plug In! This was as easy as plugging into the new outlet box and marveling at the quick operation. Four hours later, we had the 50-gallon tank at 140 degrees. The water heater has been humming along for four months without a peep from our Airbnb guests. It’s very quiet — a decibel reader showed only 43 from a couple feet away, which is equivalent to a quiet dishwasher. We monitor its performance through the Rheem app, and not only is it ridiculously efficient (using a mere 65 kWh in the first month) but it’s almost always completely full of hot water.
We paid a total of $3,258, including $2,533 for the water heater, $545 for the plumber, and $180 for parts. The product itself is admittedly expensive, but the installation costs were extremely low and on par (if not lower than) a standard water heater installation. The first 120-volt field study, by New Buildings Institute (Joe’s employer, for full disclosure), found that California installation costs ran between $2,600 and $4,600. Our Ohio installation was a quarter of that.
There are 30% tax credits for heat pump water heaters. If this was our primary residence, these tax credits would have lowered our total cost by $977 to a total of $2,281. That is remarkably close to the $2,000 average installation cost of standard gas and electric resistance water heaters as reported by Clear Seas Research. This brings the 120-volt heat pump water heater close to upfront cost parity with gas water heaters. Keep in mind the average operating costs for a heat pump water heater are $117/year compared to gas water heaters that average $325/year.
After following the development of the 120-volt plug-in heat pump water heater for a couple years, we had high expectations. Except for the ordering process, you might say we were blown out of the water. Our experience proves that there is now a heat pump water heater option that’s easy to install, runs exclusively on heat pump mode, plugs into a standard outlet, and of course heats all the water you could want. It allows almost anyone to easily remove a gas water heater from their home and paves the way towards a cleaner, more efficient, cheaper, decarbonized home.
This article is part of a series called Decarbonize Your Life. With modest steps and a middle-class income, our family has dramatically reduced emissions and is sequestering what remains through a small reforestation project. Our life is better for it. If we can do it, you can too.
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