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Heat Pump Water Heater Calculator
Tell us who lives there, what heats your water now and where the new tank would go. Get the tank size you need, the yearly cost now against a heat pump at your state's electric rate, the payback, a fit check for the space, and the heat pump water heaters that match.
Updated Oct 24, 2026
- Answer a few questions
- See the math behind every number
- Get models that actually fit
Every heat pump water heater this tool can recommend
Sorted by tank size. UEF and first-hour ratings are from each listing, maker spec sheet or ENERGY STAR certification.
Senville 50-gallon hybrid heat pump water heater
- ENERGY STAR
- electric
- 50 gallons
- 69 gal first hour
+2 moreFewer
- 4.5 kW backup element
- UL and AHRI certified
A 50-gallon ENERGY STAR heat pump water heater with a 3.75 UEF and a 69-gallon first-hour rating, for small to medium households.
- 3.75 UEF, ENERGY STAR certified
- 69 gallons first-hour rating
- 10-year compressor warranty
- 7-year parts warranty
- Maker does not list the water connection size on the listing
$1,000 to $2,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Rinnai REHP50 50-gallon heat pump water heater
- ENERGY STAR
- electric
- 30 A of breakers
- 50 gallons
+3 moreFewer
- 73 gal first hour
- 240V / 30 A
- 10-year tank and parts warranty
A 50-gallon ENERGY STAR heat pump water heater with a 3.75 UEF and a 73-gallon first-hour rating, for households of 3 to 4 replacing an electric tank.
- 3.75 UEF, ENERGY STAR certified
- 73 gallons first-hour delivery
- Runs on a 240V, 30 A circuit
- A tank, so it needs floor space
- 1-year labor warranty
$1,000 to $2,000, live price on Amazon
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ACiQ 50-gallon hybrid heat pump water heater with Wi-Fi
- electric
- 50 gallons
- 69 gal first hour
- 49.5 dBA
+1 moreFewer
- Wi-Fi
A 50-gallon heat pump water heater with a 3.75 UEF, Wi-Fi control and a 49.5 dBA sound rating, for households of 3 to 5.
- 3.75 UEF, 69 gallons first-hour rating
- 49.5 dBA, Wi-Fi app control
- 12-year tank and parts warranty with online registration
- Maker asks for 700 to 1,000 cu ft of air around it
- Not for unheated spaces that drop below 37 F
$1,000 to $2,000, live price on Amazon
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Stiebel Eltron Accelera 220 E 58-gallon heat pump water heater
- electric
- 15 A of breakers
- 58 gallons
- 50.3 gal first hour
+2 moreFewer
- 240V / 15 A
- 1 in. NPT connections
A 58-gallon heat pump water heater that runs on a 15 A, 240V circuit, for one or two people with modest peak demand.
- Needs only a 15 A, 240V breaker
- 52 dB(A) at 3.3 ft (maker spec)
- Condenser wraps the outside of the tank, no direct contact with potable water
- 50.3 gallons first-hour rating, low for its size
- 3.115 UEF, below the other heaters here; 27 1/8 in. wide
Over $2,000, live price on Amazon
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Show all 6 modelsShow fewer
Rinnai REHP65 65-gallon heat pump water heater
- ENERGY STAR
- electric
- 30 A of breakers
- 65 gallons
+3 moreFewer
- 80 gal first hour
- 240V / 30 A
- 10-year tank and parts warranty
A 65-gallon ENERGY STAR heat pump water heater with an 80-gallon first-hour rating, sized for households of 4 to 5.
- 3.9 UEF on its ENERGY STAR listing
- 80 gallons first-hour rating
- Runs on a 240V, 30 A circuit, 3/4 in. NPT connections
- The Amazon title says 4.00 UEF; the ENERGY STAR listing says 3.9
- 1-year labor warranty
$1,000 to $2,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Rinnai REHP80 80-gallon heat pump water heater
- ENERGY STAR
- electric
- 30 A of breakers
- 80 gallons
+3 moreFewer
- 91 gal first hour
- 240V / 30 A
- 10-year tank and parts warranty
An 80-gallon ENERGY STAR heat pump water heater with a 4.0 UEF and a 91-gallon first-hour rating, for households of 5 or more.
- 4.0 UEF on its ENERGY STAR listing
- 91 gallons first-hour rating
- Runs on a 240V, 30 A circuit, 3/4 in. NPT connections
- About 25.7 in. wide and 74.6 in. tall (maker spec)
- 1-year labor warranty
Over $2,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Some of these links pay us a commission and some do not; each card says which. Commissions do not affect which models the tool picks or how it ranks them. See our disclosure.
How this calculator works
- Peak hour. The DOE "Sizing a New Water Heater" worksheet: 10 gallons a shower, 4 for sink use, 6 for a dishwasher load, 7 for a clothes washer, in your busiest hour. A heater's first-hour rating (on its EnergyGuide label) must be at least that.
- Tank size. Makers' household charts (Rinnai: 50 gallons for 3 to 4 people, 65 for 4 to 5, 80 for 5 or more), stepped up when your peak hour is beyond a class's typical first-hour rating.
- Daily use. The DOE Uniform Energy Factor test (10 CFR 430, Subpart B, Appendix E) draw patterns: 38 gallons a day for one person, 55 for two or three, 84 for four or more. You can type your own number.
- Energy. Gallons a day x 8.24 lb x 67 F rise (58 F in, 125 F out, the test conditions) x 365, divided by UEF. Heat pump UEFs come from each heater's ENERGY STAR listing or spec sheet.
- Your heater now. A new 50-gallon tank at the federal minimum UEF for your draw pattern (10 CFR 430.32(d)): about 0.92 to 0.93 electric, 0.50 to 0.63 gas and propane. Older tanks do worse, so real savings are usually higher.
- Cost and payback. Electricity at your state's EIA average residential rate; gas at 100,000 BTU a therm and propane at 91,500 BTU a gallon at the prices you enter. Payback = (heater price + your install quote - rebates) / yearly savings. The federal 25C credit no longer applies to installs after 2025.
- Fit. About 700 cu ft of air, a space that stays above about 40 F, a drain for condensate, and a 240V circuit. These are the makers' installation requirements; the installation manual for your model is the final word.
Worked examples
Family of four replacing an electric tank, US average rate
- 4 people; 2 showers, sink use and the dishwasher in the busiest hour
- Electric tank, 17.3 c/kWh
- 1,200 cu ft basement that stays above 50 F, floor drain
A 50-gallon heat pump tank. About $923 a year now, $229 with a heat pump: $694 saved.
Peak hour: 10 + 10 + 4 + 6 = 30 gallons, well under the 69 to 73-gallon first-hour rating of a 50-gallon heat pump tank. On the DOE high-use pattern (84 gallons a day, 67 F rise) the water takes about 4,961 kWh of heat a year. A new electric tank at the federal minimum UEF of 0.93 uses 5,334 kWh ($923); a UEF 3.75 heat pump uses 1,323 kWh ($229). The existing 240V circuit carries over, so at $1,000 to $2,000 for the heater the payback is roughly two to three years.
Couple with a natural gas tank in Ohio
- 2 people; 2 showers and sink use in the busiest hour
- Natural gas at $1.50 a therm, Ohio rate 17.0 c/kWh
- 800 cu ft basement, 40 to 50 F in winter, no floor drain
A 50-gallon heat pump tank saves about $148 a year, so payback is about a decade on the heater alone.
Peak hour is 24 gallons. On the DOE medium-use pattern (55 gallons a day) a gas tank at the federal minimum UEF of 0.563 burns about 197 therms ($295 a year). A UEF 3.75 heat pump uses about 866 kWh ($147). The $148 a year is real but slow, and the switch needs a new 240V circuit plus a condensate pump. Gas to heat pump pays off fastest with cheap electricity, expensive gas, or an old tank well below today's minimum.
Six people on propane in Vermont
- 6 people; 4 showers, sink, dishwasher and a warm wash in the busiest hour
- Propane at $2.80 a gallon, Vermont rate 22.9 c/kWh
- Basement, above 50 F
An 80-gallon heat pump tank. About $826 a year on propane, $284 with a heat pump: $542 saved.
Peak hour: 40 + 4 + 6 + 7 = 57 gallons, and six people put it in the 80-gallon class (91-gallon first-hour rating). At 84 gallons a day a propane tank at UEF 0.627 burns about 295 gallons ($826). A UEF 4.0 heat pump uses about 1,240 kWh ($284), even at Vermont's high rate. Propane is expensive heat, which is why the switch pays here.
Frequently asked questions
What size heat pump water heater do I need?
Add up the hot water in your busiest hour (DOE uses 10 gallons a shower, 6 for a dishwasher load, 7 for a clothes washer, 4 for sink use) and pick a heater whose first-hour rating is at least that. Rinnai's chart puts 3 to 4 people on a 50-gallon tank, 4 to 5 on 65 gallons and 5 or more on 80; 50 gallons is also the smallest common size, so one or two people land there too.
How much does a heat pump water heater save?
ENERGY STAR estimates a certified heat pump water heater saves a family of four about $550 a year over a standard electric tank. Our method gives $694 at the 17.3 cent US average rate: about 4,000 kWh a year less, worth about $550 at roughly 13.7 cents. Savings over gas or propane depend on your fuel price.
Is there still a tax credit for heat pump water heaters?
Not a federal one for new installs. The 25C credit (30% of cost, up to $2,000) ended for property placed in service after December 31, 2025, under the One Big Beautiful Bill Act. State HEAR rebates (up to $1,750 for income-qualified households, where your state has launched the program) and utility rebates are still offered in many areas.
How much space does a heat pump water heater need?
Most makers ask for about 700 cubic feet of air around it, for example a 10 x 10 ft room with a 7 ft ceiling, or a louvered door or duct kit to borrow air from next door. It cools and dries the room it sits in, which suits a basement or garage and is a drawback in a small closet.
Can a heat pump water heater go in a cold garage?
Only where the space stays above roughly 40 F. The Rinnai units run the compressor down to about 37 F and the Stiebel Eltron Accelera down to 42 F; below that they heat with the electric element at standard-tank cost. A garage that freezes can damage the tank and pipes.
Does a heat pump water heater need a special circuit?
Standard models run on a 240V circuit, usually 30 A (the Stiebel Eltron Accelera 220 E uses 15 A), so replacing an electric tank usually reuses the existing circuit. Replacing gas or propane means running a new 240V circuit, or choosing one of the newer 120V plug-in models from Rheem, A.O. Smith or GE.
Do heat pump water heaters need a drain?
Yes. The heat pump pulls moisture out of the air and drips condensate whenever it runs, so it needs a floor drain, laundry sink or a condensate pump. It also needs the usual pan and relief valve line, and an expansion tank on most homes with a backflow preventer or pressure-reducing valve.
What does UEF mean on a water heater?
Uniform Energy Factor, from the DOE test procedure: the heat delivered to the water divided by the energy the heater used, over a simulated day of draws. A standard electric tank is about 0.92, a standard gas tank about 0.56 to 0.63, and heat pump tanks 3 to 4, meaning three to four units of heat for each unit of electricity.
Marcus Reed
Founder and Editor, CrunchYourDollars
Marcus Reed builds the sizing tools on CrunchYourDollars. He is a software engineer with a long-running PC hardware and power supply habit, which is where the watts, watt-hours and surge math on this site comes from. Product specs are pulled from manufacturer data sheets, electricity rates from the U.S. Energy Information Administration, and water chemistry rules from the Water Quality Association. He is not a licensed electrician or plumber: the tools show the math and the matching models so you can make the call, and anything involving your electrical panel should be checked by a licensed pro.
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