Gas-Fired Water Heater Screening Tool

This calculator determines the energy consumption and payback period for standard commercial and ultra-efficient commercial condensing water heaters and compares them with consumption and payback for residential models. By necessity, this screening model makes simplifying assumptions, so use it for initial screening only. For more accurate performance predictions, conduct a more detailed analysis that includes additional factors such as actual usage patterns, hot water loads, and part-load performance of equipment.

The values already entered in certain cells are examples, generally using national average data. Replace them with values that correspond to your own situation (for instance, if you know it, enter your actual electricity cost in $/kWh).

Go back to the gas-fired tank water heaters topic.

Average daily draw (gallons)
Natural gas cost ($/therm)
Electricity cost ($/kWh)
Water heater type
  Residential (base case) Commercial Ultra-efficient
Thermal efficiency
Energy factor
Purchase price ($)
Annual gas consumption (therms)a,b
Annual gas cost ($)
Annual electricity consumption (kWh)c
Annual electricity cost ($)
Annual operating cost ($)
Annual operating cost savings ($)
Incremental equipment cost ($)
Simple payback period (years)

Notes: F = Fahrenheit; h = hour; kWh = kilowatt-hour; NA = not applicable.
a. Assumes that each water heater is properly sized to meet the loads; residential case features two 50-gallon tanks, 120,000-Btu/h burner; commercial case features one 37-gallon tank, 160,000-Btu/h burner; ultra-efficient unit features one 60-gallon tank, 125,000-Btu/h burner.
b. Annual hot water consumption based on operation six hours per day, 365 days per year, 100°F rise in water temperature.
c. Based on 500-W load, six hours per day, 365 days per year.

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