How does this heat pump water heater calculator estimate savings?

It estimates annual heat needed for hot water from gallons, days, and temperature rise. It then divides that heat by each water heater UEF or COP-like efficiency, multiplies by local energy prices, and compares annual operating cost.

What is UEF for a water heater?

UEF means Uniform Energy Factor. A higher UEF means less purchased energy is needed for the same hot-water service. Heat pump water heaters can have UEF values well above 1 because they move heat instead of only making heat with resistance elements.

Are heat pump water heaters always cheaper to run?

They are usually much cheaper than standard electric resistance water heaters, but comparison with gas depends on electricity price, gas price, gas water heater UEF, heat pump UEF, and installation conditions.

Should I enter full installed cost or upgrade premium?

For payback, enter the cost you want savings to recover. If you are replacing a failed water heater anyway, the incremental premium after rebates is often more useful than the full project cost.

Does this include space heating or cooling effects?

No. A heat pump water heater cools and dehumidifies the space around it. In conditioned rooms, that can affect heating and cooling loads, so use this as a screening estimate rather than a whole-home energy model.

No. The calculator runs locally in your browser and does not send your water use, cost, or utility inputs to a server.

Heat Pump Water Heater Savings Calculator

Estimate annual bill savings, CO2 reduction, incentives, and simple payback when switching to a heat pump water heater. Everything runs locally in your browser.

Last updatedJune 30, 2026

Core methodHot-water heat load x UEF and fuel rates

SourcesDOE, ENERGY STAR, EPA, and EIA labels

PrivacyNo server upload or input tracking

Inputs

Hot water demand

Mixed hot-water use (gallons/day) Temperature rise (deg F) Use days per year

Temperature rise is hot tank temperature minus incoming cold water temperature. Example: 120 F tank and 50 F incoming water gives 70 F.

Water heater efficiency

Current water heater Current UEF or effective efficiency Heat pump water heater UEF

UEF values on product labels are best. Heat pump water heaters often land around 2 to 4+ UEF depending on model and conditions.

Rates and CO2 factors

Currency Electricity price (per kWh) Gas price (per therm)

Grid CO2 (kg/kWh) Gas CO2 (kg/therm) kWh per therm

Use your utility bill for rates. Grid CO2 varies by location; gas CO2 here covers combustion, not unburned methane leaks.

Project cost

Installed cost or upgrade premium Rebates / tax credits Analysis period (years)

For payback, enter the cost you want operating savings to recover. If replacing a failed unit anyway, use the incremental premium after incentives.

Results

Enter your water heater assumptions, then calculate.

How the Savings Estimate Works

This calculator estimates the annual heat needed to supply your hot water, then compares how much purchased energy your current water heater and a heat pump water heater would use. Heat pump water heaters use electricity to move heat into the tank, so their UEF can be well above 1.

Annual gallons = gallons per day x days per year Hot-water heat = gallons x 8.34 lb/gal x temperature rise F / 3,412.142 Btu per kWh Current electric kWh = hot-water heat / current UEF Current gas therms = hot-water heat / current UEF / kWh per therm Heat pump water heater kWh = hot-water heat / HPWH UEF Annual savings = current annual energy cost - HPWH annual electricity cost

This is a screening calculator, not a contractor quote, utility rebate determination, or whole-home energy model. Real results vary with draw pattern, tank size, setpoint, ambient room temperature, ducts, backup resistance use, local tariffs, and installation quality.

Assumptions and Sources

DOE Energy Saver explains that heat pump water heaters move heat instead of generating heat directly and can be two to three times more energy efficient than conventional electric resistance water heaters.
ENERGY STAR notes that heat pump water heaters are also called hybrid electric water heaters and gives installation guidance such as 40 F to 90 F spaces and adequate surrounding air volume.
EPA greenhouse gas equivalencies documentation gives natural gas combustion emissions of about 0.0053 metric tons CO2 per therm, which this tool enters as 5.30 kg CO2 per therm.
EIA Electric Power Monthly tables are a source for current electricity price references. Your own marginal utility rate is usually better for purchase decisions.

References: DOE Energy Saver heat pump water heaters, ENERGY STAR heat pump water heaters, EPA greenhouse gas equivalencies references, and EIA Electric Power Monthly.

FAQs

What hot-water use should I enter?

If you do not have metered hot-water data, use a rough daily household estimate and test a range. Larger households, long showers, laundry, and dishwashing raise the load.

What UEF should I use?

Use the yellow EnergyGuide label, AHRI listing, manufacturer specification, or product finder value for the exact model when available. Defaults are editable starter values.

Why does gas sometimes look cheaper?

Gas can have a low price per delivered heat unit. A heat pump water heater beats gas on operating cost only when its UEF and electricity price overcome the gas rate and current gas efficiency.

Why is payback blank or "no simple payback"?

If annual savings are zero or negative, operating savings do not recover the entered net project cost. Try your real rates, a different UEF, or an incremental-cost comparison.

Should I include fixed utility charges?

Use variable energy rates for running-cost comparison. Include fixed gas account fees only if replacing gas water heating lets you remove gas service entirely.