- "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.