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April 9, 2008
Energy Star Certified Water Heating
Energy Star has released information about the Energy Star Water Heater criteria that will take effect in January 2009. This is exciting news, as water heaters had not been Energy Star certified prior to this, and it will help people make informed decisions about products' energy efficiency and potential long-term cost savings. Depending on the type of water heater, choosing an Energy Star model is estimated to save 7.3 to 55% of typical annual energy use for water heating. This relates to $26 to $277 a year.
The criteria all relate to the Energy Factor (EF), with some added requirements as needed for each technology. The EF more or less relates to the overall efficiency of the unit and higher is better. The highest possible EF for electric resistance or gas heating is 1. The heat pump water heaters can see EF's greater than 1 because of they pull heat from their environment in addition to the electrical power input to produce more heat energy than the electrical energy input.
Most common here in the US are water heaters that utilize some sort of tank storage for the hot water. This allows for the burner or heating element to be smaller, but the tank loses heat to its environment continuously, lowering the efficiency. Most solar thermal systems for water heating of this type also use some sort of thermal storage tank, as do most of the heat pump water heaters I've seen. A lot of advantage can be gained by using an on-demand, or tankless, water heater. There are some disadvantages as well. Check out the Department of Energy's website dedicated to water heaters if you wish to learn more about the different technologies and their advantages/disadvantages.
Here is a rundown of the minimum Energy Factor levels required for Energy Star certification for residential water heaters in 2009:
* Gas storage water heaters: EF of 0.62
* Gas condensing water heaters: EF of 0.80 (plus some other performance caveats)
* Whole-home gas tankless water heaters: EF of 0.82 (plus some other performance caveats)
* Heat pump water heaters: EF of 2.0
Solar thermal water heaters have requirements of a minimum solar fraction of 0.50 and a Solar Rating and Certification Corporation (SRCC) OG-300 certification.
Check out the DOE press release and these two blog entries for details and other ways of looking at this:
DOE press release
groovy green
CleanTechnica
Posted by Eric Helton at 11:45 AM | Comments (6)
