Energy factor

Water heaters

The energy factor metric only applies to residential water heaters, which are currently defined by fuel, type, and input capacity. Generally, the EF number represents the thermal efficiency of the water heater as a percentage, since it is an average of the ratio of the theoretical heat required to raise the temperature of water drawn to the amount of energy actually consumed by the water heater.

Test procedure

The energy factor for residential water heaters is determined using the results from the 24-hour simulated use test. During the test 64.3±1.0 gallons of water are drawn from the water heater in six equally spaced draws that begin one hour apart. The hot water flow rate for each draw is 3.0±0.25 gallons per minute. After the beginning of the last draw a standby period of 18 hours follows. During the test, the test conditions must be operated at a specified value and accuracy. Heat pump water heaters (HPWHs) have different values specified for ambient air temperature and relative humidity.

From the standard test procedure, the energy factor is defined as : EF=\sum\limits_{i=1}^6 \frac{M_i C_{pi}\left( 135^\circ F-58^\circ F\right)}{Q_{dm}}, where Q_{dm} is the modified daily water heating energy consumption (Btu), M_i is the mass withdrawn from the ith draw (lb), and C_{pi} is the specific heat of the water of the ith draw Btu/lb°F, evaluated at the midpoint between 58 and.

FOLLOWING SAYS IT IS THE EQUATION FOR Qdm, BUT IT IS NOT. IT IS THE EQUATION FOR Qhw, which is only a component of Qdm: The modified daily water heating energy consumption is defined as : Q_{dm}=\sum\limits_{i=1}^6 \frac{M_i C_{pi}\left( \overline{T}{del,i}-\overline{T}{in,i}\right)}{\eta_r}, where \overline{T}{del,i} is the average delivery temperature of the ith draw (°F) as measured during the test, \overline{T}{in,i} is the average inlet temperature of the ith draw (°F) as measured during the test, and \eta_r is the recovery efficiency of the water heater.

Uniform energy factor (UEF)

the Uniform Energy Factor (UEF) is newest measure of water heater overall efficiency according to the Department of Energy’s test method outlined in 10 CFR Part 430, Subpart B, Appendix E.

Energy conservation standards

Minimum federal energy conservation standards are defined by fuel, type, and rated storage volume. All standards are calculated as a function of the rated storage volume V in gallons. The current conservation standards are less efficient than the standards that go into effect in 2015.

Dishwashers

The energy factor for dishwashers is defined as "the number of cycles per kWh of input power ."

Clothes washers

The energy factor for clothes washers, is defined as "the cubic foot capacity per kWh of input power per cycle."

Clothes dryers

The energy factor for clothes dryers is defined as "the number of pounds of clothes dried per kWh of power consumed."

References

References

1. "Federal Tax Credits for Consumer Energy Efficiency: Definitions". [[U.S. Environmental Protection Agency]].
2. "Statutory Authorities and Rules". [[U.S. Department of Energy]].
3. "ESTIMATING COSTS AND EFFICIENCY OF STORAGE, DEMAND, AND HEAT PUMP WATER HEATERS". US Dept of Energy.
4. "Standards and Test Procedures". U.S. Department of Energy.
5. "Residential Water Heaters". U.S. Department of Energy.
6. (11 May 1998). "10 CFR Part 430 Energy Conservation Program for Consumer Products: Test Procedure for Water Heaters; Final Rule". Federal Register.
7. (16 April 2010). "10 CFR Part 430 Energy Conservation Program: Energy Conservation Standards for Residential Water Heaters, Direct Heating Equipment, and Pool Heaters; Final Rule". Federal Register.
8. (17 January 2001). "10 CFR Part 430 Energy Conservation Program for Consumer Products: Energy Conservation Program for Consumer Products: Energy Conservation Standards for Water Heaters; Final Rule". Federal Register.