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 the ROI calculation works

1. 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.
2. 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×.
3. 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.
4. 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.