Homeowners
Save Energy
Energy Ratings for Water Heaters
Water heaters have two important certified ratings that tell you the capacity you need and how energy you could save: First Hour Rating and Energy Factor. Both of these ratings are certified through performance certification programs administered by the Air-Conditioning, Heating and Refrigeration Institute. These certified ratings are listed in AHRI’s Directory of Certified Product Performance.
The EnergyGuide, which is a big yellow sticker located on your water heater, has the unit’s First Hour Rating and compares the average yearly operating costs of different water heaters, using the same criteria for all models tested.
Understanding First Hour Rating
The First Hour Rating is an indicator of how much hot water a particular water heater model can provide. The rating, in gallons of usable (desired temperature) hot water is reached by combining the amount of usable hot water stored in the tank plus how many gallons of usable hot water the water heater can generate in one hour of operation.
For example, if a 40-gallon natural gas water heater stores 31 gallons of usable hot water and can deliver 41 gallons of usable hot water in the first hour, its First Hour Rating is 72 gallons.
Understanding Energy Factor
The water heater’s Energy Factor (EF) is an overall efficiency rating of the water heater. The EF is a number with a decimal point usually listed on a separate label beside the EnergyGuide. The higher the EF, the more efficient it is.
Water heaters with high EF ratings may cost more initially, but save energy and money in the long run. Eventually, they will pay for themselves through a lifetime of energy savings. Gas water heaters have energy factors between 0.5 to around 0.7. Electric models range from 0.75 to 0.95.
Replacing your old water heater can save you money because today's models are better insulated to reduce heat loss. As a result, most cost about 18 percent less to run than older models.