Heat pump
120V Plug-In Heat Pump Water Heaters
A 120V heat pump water heater plugs into an ordinary outlet, so it can replace a gas tank without a new 240 V circuit, but it recovers slowly and is usually bought two sizes larger.
Compiled by the Tank & Tankless desk · Revised
On this page
- What is a 120V heat pump water heater?
- How is a 120V model different from a 240V heat pump?
- Does a 120V heat pump water heater need its own circuit?
- Why are 120V heat pump models sized larger?
- How fast does a 120V heat pump water heater recover?
- Is a plug-in heat pump a good gas replacement?
- Frequently asked
At a glance
- ENERGY STAR's installer guide says 120V units typically go up two sizes from the gas tank they replace, for example 40 gallons to 65.
- ENERGY STAR certifies 120 V, 15-amp integrated models at a UEF of 2.20 or more, against 3.30 for standard integrated units.
- Rheem's shared-circuit ProTerra plug-in draws 395 to 440 watts and recovers 12 gallons per hour at a 60°F rise.
- Rheem's dedicated-circuit 50-gallon plug-in lists a 15-amp breaker, 1,100 watts, UEF 3.0 and 29 gallons per hour at a 60°F rise.
- DOE's 2024 rule was written to allow "continued development and innovation with 120-V heat pump" tanks (Federal Register).
- Some 120V models need more than 700 cubic feet of air, per ENERGY STAR.
- 2.20Minimum UEF for ENERGY STAR 120 V / 15 A heat pump unitsENERGY STAR
- 40 → 65 galTypical upsizing from a gas tank to a 120V unitENERGY STAR
- 12 gphRecovery of one shared-circuit 120V model at a 60°F riseRheem
- 15 ABreaker listed for 120V plug-in modelsRheem
What is a 120V heat pump water heater?
A 120V heat pump water heater is an integrated heat pump tank with a factory power cord that plugs into a standard household outlet instead of being wired to a 240 V circuit. ENERGY STAR describes them as "plug-in 120V heat pump water heaters specifically designed for retrofit replacement of gas water heaters" (ENERGY STAR install guide). The point is to skip the panel upgrade and long wire run that a gas-to-electric swap often needs.
The heat pump itself works like any other: a compressor moves heat from room air into the water (how heat pump models work). What changes is the power budget. A 15-amp, 120 V circuit cannot feed the 4,500-watt elements a 240 V tank uses, so these units lean on the compressor and a bigger store of hot water.
How is a 120V model different from a 240V heat pump?
A 120V heat pump model differs from a 240 V one in power draw, backup heat, recovery speed and usually tank size. Rheem's 240 V ProTerra units specify a 30-amp breaker, 4,500-watt backup elements and a recovery rate of 26 to 27 gph at a 90°F rise. Its 120 V plug-in versions list a 15-amp breaker, run in heat-pump mode (plus a vacation setting) and recover 12 to 29 gallons per hour at a gentler 60°F rise (Rheem 120V shared-circuit sheet).
Efficiency is close. ENERGY STAR's Version 5.0 criteria set the floor at UEF 2.20 for "Integrated HPWH, 120 Volt / 15 Amp Circuit" models and 3.30 for standard integrated units (ENERGY STAR key criteria). Rheem's own 120 V models list UEF 2.8 to 3.46, against 3.83 to 4.07 for its 240 V line.
| Model type | Breaker | Average or element wattage | UEF | First-hour rating | Recovery |
|---|---|---|---|---|---|
| 120V shared circuit, 40–80 gal | 15 A | 395–440 W | 2.8–3.46 | 45–84 gal | 12 gph at 60°F rise |
| 120V dedicated circuit, 50 gal | 15 A | 1,100 W | 3.0 | 51 gal | 29 gph at 60°F rise |
| 240V hybrid, 40–80 gal | 30 A | 4,500 W elements | 3.83–4.07 | 60–87 gal | 26–27 gph at 90°F rise |
Does a 120V heat pump water heater need its own circuit?
It depends on the model: some 120V heat pump water heaters need a dedicated circuit and others share an outlet with other loads. ENERGY STAR flags this as one of the ways 120V models "can differ," along with air space. Rheem sells both: its dedicated-circuit 50-gallon model lists a 15-amp minimum breaker and 1,100 watts on average, while its shared-circuit line "plugs directly into a standard wall outlet" at 395 to 440 watts (Rheem dedicated-circuit sheet).
The manual decides, not the plug. Where a time-delay fuse protects the circuit, Rheem calls for that type. An electrician can confirm whether the outlet near an old gas tank is on a circuit with spare capacity, and whether local code wants a GFCI or other protection there.
Why are 120V heat pump models sized larger?
120V heat pump models are sized larger because they make hot water slowly, so the tank has to hold more of it. ENERGY STAR's guide says "120V units need to be sized-up two sizes from a gas water heater (40-gallon gas to a 65 gallon)." A gas burner refills a tank quickly; a small compressor on a 15-amp circuit takes hours to do the same.
Makers stretch the stored volume in two ways. One is the bigger tank. The other is a hotter tank with a built-in mixing valve: Rheem's shared-circuit units store water at 128 to 140°F and blend it down at the outlet, which is how its 80-gallon model reaches an 84-gallon first-hour rating. A mixing valve at the tank also cuts scald risk from the hotter stored water (temperature setting and scalds).
The larger tank needs floor space and air. ENERGY STAR notes that "Some 120V models designed to replace gas units require more than 700 cubic feet," so a closet that held a 40-gallon gas tank may not suit a 65-gallon plug-in. The space and climate page covers room checks.
How fast does a 120V heat pump water heater recover?
A 120V heat pump water heater recovers at roughly 12 to 29 gallons per hour at a 60°F rise, depending on whether it is a shared- or dedicated-circuit design. Rheem's shared-circuit models list 12 gallons per hour with a 4,200 Btu/h compressor; its dedicated-circuit 50-gallon model lists 29 gallons per hour with a 12,000 Btu/h compressor. For context, DOE's sizing worksheet counts 20 gallons of hot water per shower, meaning a run of back-to-back morning showers draws mostly on what is already in the tank (DOE Energy Saver (archived)).
That is why the first-hour rating matters more than tank size when shopping. DOE says to pick a model whose first-hour rating at least matches the household's peak-hour demand. The worksheet is on the water heater sizing page.
Is a plug-in heat pump a good gas replacement?
A plug-in heat pump is a good gas replacement when the room is large enough, the household's peak use fits the first-hour rating, and running a 240 V circuit would be costly. It removes the flue and gas combustion from the house and needs only an outlet, a condensate drain and the usual tank plumbing. DOE notes that a heat pump unit "might have lower energy costs than a gas-fired conventional storage water heater" even where gas is cheaper per unit of energy (DOE Energy Saver (archived)).
It suits fewer homes when demand is heavy or the space is tight. Large families with simultaneous showers, cold garages and small closets push toward a 240 V model or a different fuel. The broader trade-offs are in gas vs electric.
Money changed in 2026: the federal 25C credit is gone for units placed in service after 2025, per the IRS. HEEHR rebates (capped at $1,750, run by states) and utility programs, often $300 to $1,000, are what remain.
Sources and scope
Sources: ENERGY STAR's 2024 installer guide and Version 5.0 key criteria, three Rheem ProTerra spec sheets (120V dedicated, 120V shared, 240 V, 2025 forms), the 2024 DOE final rule, archived DOE Energy Saver selection and sizing pages, and the IRS 25C notice, checked October 2026. Rheem is used because its sheets list both 120V types; other makers' figures differ. Not used: retailer listings, reviews and owner forums.
Frequently asked
Can a 120V heat pump water heater run on an extension cord?
Makers' plug-in designs are built to plug directly into a wall outlet; the Rheem sheets describe direct plug-in. Follow the manual, which is the document a warranty claim will be checked against.
Do 120V heat pump water heaters have backup heating elements?
The Rheem plug-in sheets list only heat-pump and vacation modes, unlike its 240 V hybrids with 4,500-watt elements. Check the spec sheet of any model considered, since that is where backup heat is listed.
What size 120V heat pump replaces a 50-gallon gas tank?
ENERGY STAR's rule of thumb is two sizes up, which would point to about 80 gallons for a 50-gallon gas tank. A peak-hour calculation against the model's first-hour rating is the better test.
Is a 120V heat pump water heater eligible for ENERGY STAR?
Yes. ENERGY STAR has a separate category for integrated 120 V, 15-amp units with a minimum UEF of 2.20.
Will a 120V unit trip the breaker on a shared circuit?
Shared-circuit models are designed to sit on an outlet with other loads, at roughly 400 watts. A dedicated-circuit model drawing about 1,100 watts needs its own 15-amp circuit, per its maker.
Does a 120V heat pump need a condensate drain?
Yes. Rheem's plug-in models have 3/4-inch condensate connections, and the water must reach a drain or a condensate pump.
Related reading
Start over at the water heater type index · more in Heat pump