water heating costs, estimates, and comparisons
Before you can choose and compare the costs of various models, you need to determine the correct size water heater for your home.
Calculating annual operating costTo estimate the annual operating cost of a storage, demand (tankless or instaneous), or heat pump (not geothermal heat pump) water heater, you need to know the following about the model:
Then, use the following calculations:
For gas and oil water heaters
You need to know the unit cost of fuel by BTU (British thermal unit) or therm. (1 therm = 100,000 BTU)
365 × 0.4105/EF × fuel cost (therm) = estimated annual cost of operation
Where the constant of 41045 BTU/day (0.4105 therm/day) is the average daily energy use of a standard gas or oil water heater.
Example: A natural gas water heater with an EF of 0.57 and a fuel cost of $0.00000619/Btu
For electric water heaters, including heat pump units
You need to know or convert the unit cost of electricity by kilowatt-hour (kWh).
Where the constant of 12.03 kWh/day is the average daily energy use of a standard electric hot water heater.
Example: A heat pump water heater with an EF of 2.0 and a electricity cost of $0.0842/kWh
Comparing costs and determining paybackOnce you know the purchase and annual operating costs of the water heater models you want to compare, you can use the table below to determine the cost savings and payback of the more energy-efficient model(s).
Comparison of two gas water heaters with a local fuel cost of .60 per therm.
Other costsIf you want to include installation and maintenance costs, consult the manufacturer(s) and a qualified contractor to help estimate these costs. These costs will vary among system types and sometimes even from water heater model to model.
Related category• HEATING TOPICS
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