Tankless Water Heater ROI Calculator
Estimate your annual energy savings and payback period using your state's actual gas and electricity rates from the U.S. Energy Information Administration.
How does the ROI calculation work?
- State energy rates. Your ZIP maps to a state, which pulls the EIA 2024 average residential rate for natural gas ($/therm) and electricity (¢/kWh). Hawaii and California consistently run 2–3× the national average — the calculator reflects that.
- Baseline usage. The DOE/ENERGY STAR baseline is 258 therms/year for a gas tank heater serving a family of four, or 4,500 kWh/year for an electric tank. Household size scales this linearly from a single-person factor of 0.45× to a 5+ person factor of 1.30×.
- Efficiency factors. Standard tank gas = 0.67 EF. Tankless gas = 0.95 UEF. Electric tank = 0.92 EF. Tankless electric = 0.99 UEF. Heat pump water heater = 3.50 UEF (DOE-certified). The calculator divides baseline usage by EF to get actual energy consumed.
- IRA 25C credit. The Inflation Reduction Act (2022) provides a 30% federal tax credit, capped at $600 for qualifying tankless gas heaters and $2,000 for heat pump water heaters, through 2032. This is deducted from the installation premium before calculating payback.
What affects real-world payback?
Installation cost varies by home. Gas tankless units need a larger gas line (often ¾" or 1") and dedicated venting — homes with older 3/8" gas supplies may face an additional $300–600 pipe upgrade. Heat pump water heaters need 1,000+ cubic feet of ambient air space and an available 240V circuit. Both factors can extend the payback period beyond this calculator's premium estimate.
For methodology and data sources: methodology page.
What else do people ask about tankless ROI?
Where do the energy rates in the calculator come from?
Your ZIP maps to a state, which pulls the EIA 2024 average residential rate for natural gas and electricity. Hawaii and California consistently run 2-3 times the national average, and the calculator reflects that.
How does household size affect the savings estimate?
The DOE/ENERGY STAR baseline usage (258 therms/year for a gas tank heater, or 4,500 kWh/year for an electric tank) is for a family of four. Household size scales that baseline from a factor of 0.45x for a single person up to 1.30x for a household of five or more.
What is the difference between EF and UEF efficiency ratings?
EF (energy factor) rates standard tank units, such as 0.67 for gas and 0.92 for electric. UEF (uniform energy factor) rates tankless and heat pump units, such as 0.95 for tankless gas, 0.99 for tankless electric, and 3.50 for a DOE-certified heat pump. The calculator divides baseline usage by the relevant factor to estimate energy consumed.
Does the calculator include the federal tax credit?
Yes. It applies the IRA Section 25C federal tax credit, a percentage of cost subject to per-unit caps for qualifying tankless gas and heat pump water heaters through 2032, deducting it from the installation premium before calculating payback.
What could make the real-world payback longer than the calculator estimates?
Homes with older, smaller gas supply lines may need a larger gas line and dedicated venting for a tankless unit. Heat pump water heaters need at least 1,000 cubic feet of ambient air space and an available 240V circuit. Both factors can extend the payback period beyond the calculator's premium estimate.
Sources
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