Energy Cost Calculator for Electric and Gas Water Heaters

Vary equipment size, energy cost, hours of operation, and /or efficiency level.

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, FEMP 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.