Ef is determined by the department of energy s test method outlined in the 10 cfr parts 200 to 499 edition revised as of january 1 2014.
95 energy factor water heater.
As of september 1 2010 a water heater needs to have an energy factor of 0 67 or higher in order to qualify.
Due to inconsistent unreliable interpretations of high efficiency ef ratings across national brands all water heating manufactururers are now required to comply with the new doe testing procedures and rating standards.
An older measure of water heater overall efficiency that is being phased out due to new test methods for water heaters.
The best electric resistance storage water heaters achieve an energy factor of 0 95 and the best electric resistance tankless water heaters achieve an energy factor of 0 99.
Beginning june 12 2017 ef ratings will be replaced with the new industry standard for measuring energy efficiency in water heaters called uniform energy factor uef.
This means that between 75 and 95 percent of the energy used to heat the water ends up being delivered to your taps as usable hot water.
This will give you the annual operating cost for a heat pump water heater.
The typical energy factor for a gas water heater is between 0 5 and 0 7.
What s a good water heater energy factor.
The energy factor ef indicates a water heater s overall energy efficiency based on the amount of hot water produced per unit of fuel consumed over a typical day.
Gas powered water heaters typically have an energy factor between 0 5 and 0 7.
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For example a high bin water heater with a uef of 0 95 does not perform exactly the same as that of a low bin water heater with a uef of 0 95.
2016 manufacturer s certification statement high efficiency water heater models.
The higher the ef value is the more efficient the water heater.
The energy star water heater with heat pump has an energy factor of 2 5 250 more energy efficient the doe calculator won t take a number above 95 so divide the standard standard electric water heater s annual operating cost by 250 use the key.
The perfect electric resistance water heater could not exceed an energy factor of 1 0 due to this technology s physical limitations.
Electric water heaters typically have energy factors between 0 75 and 0 95.
The uniform energy factor for residential and certain commercial water heaters refers to its efficiency when run under standardized conditions for a 24 hour period.
Expressed as a decimal the uniform energy factor is determined by running a department of energy specified simulated use test sut.
One good way to determine whether or not a water heater is energy efficient is to look for the energy star label.
Use the energy factor to determine the energy efficiency of a storage tankless or demand type water heater or heat pump water heater.
The uniform energy factor.
