Estimate U.S. household hot-water energy cost from either a transparent water-use scenario or annual energy data from an EnergyGuide label or product document. Use your actual electricity or natural-gas rate whenever possible.
Estimate hot-water running cost
Use a water-heating scenario or annual energy data from an EnergyGuide label or product document.
Energy rates
Which hot-water calculation method should you use?
Water-use scenario
This method estimates the heat required to raise a chosen number of gallons of water from an inlet temperature to a hot-water temperature. It can model electric resistance, a heat-pump water heater using a chosen COP, or natural gas using an entered efficiency assumption. Storage, standby, distribution and control losses can change actual use.
Annual electricity or natural-gas use
If an EnergyGuide label, ENERGY STAR listing or manufacturer document gives annual electricity use in kWh or annual gas use in therms, enter that value directly for a model-specific annual-cost estimate.
About UEF and heat-pump water heaters
ENERGY STAR describes Uniform Energy Factor (UEF) as the current overall-efficiency measure for water heaters. The water-use scenario asks for COP rather than treating UEF as an exact real-time COP, because heat-pump performance and operating mode vary with conditions.
Official U.S. references
- ENERGY STAR — Residential Water Heater Key Product Criteria
- ENERGY STAR — Heat Pump Water Heater Guide
- FTC — How to Use the EnergyGuide Label
- EIA — Energy units and calculators
- EIA — Residential electricity prices by state
Reviewed: 27 September 2026. Electricity state benchmarks use EIA July 2026 residential average retail prices.
Hot water running cost FAQs
Why does inlet-water temperature matter?
The larger the temperature rise between incoming water and the target hot-water temperature, the more heat is required for each gallon.
Can I use UEF as the heat-pump COP?
Not as an exact real-time conversion. UEF is an overall standardized efficiency measure, while heat-pump COP depends on operating conditions and mode.
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