This energy cost calculator for electric and gas water heaters is designed as a screening tool that estimates a water heater's lifetime energy cost savings at various efficiency levels.

Input the following data (if any parameter is missing, calculator will set to default value). Defaults
Type of Water Heater    Electric
Average Daily Usage (gallons per day)*    gallons 64*
Energy Factor†    0.92 (electric)
0.61 (gas)
Energy Cost  $ /  $0.06 per kWh
$.60 per therm
Quantity of Water Heaters to be Purchased    unit(s) 1 unit
* See assumptions for various daily water use totals.
† The comparison assumes a storage tank water heater as the input type. To allow demand water heaters as the comparison type, users can specify an input EF of up to 0.85; however, 0.66 is currently the best available EF for storage water heaters.

Performance per Water Heater Your
New Energy Factor             
Annual Energy Use             
Annual Energy Costs $<> $ $ $
Lifetime Energy Costs $ $ $ $
Lifetime Energy Cost Savings $ $ $ $
Lifetime Energy Cost Savings for Water Heater(s) $ $ $ $

Your selection of a water heater using gallon(s) per day will have a $ energy cost savings per water heater over an estimated 13 year life expectancy compared to the model.


  • "Base model" has an efficiency that just meets the national minimum standard for gas and electric water heaters.
  • Lifetime energy cost is the sum of the discounted value of the annual energy costs based on assumed water heater life of 13 years.
  • Future electricity price trends and a discount rate of 3.2% are based on Federal guidelines.
  • $0.09 per kWh for electricity is the Federal average price in the U.S.
  • $0.93 per therm for gas is the Federal average price in the U.S.
  • Hot water usage estimates:
    • Average shower (8 minutes) = 10 gallons of hot water
    • Average clothes washer (one load) = 7 gallons of hot water
    • Average dishwasher (one load) = 6 gallons of hot water
    • Average kitchen faucet flow = 2 gpm
    • Average bathroom faucet flow = 0.5 gpm
    • Average daily usage = 64 gallons of hot water.


This cost calculator is a screening tool that estimates a product's lifetime energy cost savings at various efficiency levels. Maintenance and installation costs do not vary significantly among the same product having different efficiencies; so, these costs are not included in this calculator tool. For a detailed life cycle cost analysis, the Federal Energy Management Program has developed a tool called Building Life Cycle Cost (BLCC). This downloadable tool allows the user to vary interest rates, installation costs, maintenance costs, salvage values, and life expectancy for a product or an entire energy project.