Your water heater’s efficiency is measured in EF (efficiency factor), which is determined by the amount of hot water produced per unit of fuel consumed over a typical day. For example a gas water heater with an EF of .67 is using 67% of the gas fuel to heat the water. The other 33% is being wasted. The higher the energy factor, the more efficient the water heater.
The location of the water heater is also important. Interior closets are best; water heaters located in unconditioned spaces like garages and attics should be wrapped with insulation to lessen the impact of cold air.
According to ENERGY STAR, “the average household spends about $400-$600 per year on water heating – making it the second largest energy expenditure behind heating and cooling.” See below for the different types of water heaters.
Our Energy Report Card will show you the types and locations of your water heaters, including their EF. We’ll also note whether the water heaters are insulated or not.
Solar water heaters are the most efficient type of system with a EF range of 1.2-1.8.
Electric tankless water heaters have an EF range of .96-.99.
Electric with a tank has an EF range of .95-.96.
Gas tankless water heaters’ EF range from .90-.93.
Gas with tank has a EF range of .67-.77.
- If you’re considering upgrading your water heater, Energy Star has some good resources to compare initial cost to energy savings over time.