EGEE 102
Energy Conservation for Environmental Protection

Energy Efficiency and Test Criteria


Energy Factor (EF) is the dishwasher energy performance metric. EF is expressed in cycles per kWh and is the reciprocal of the sum of the machine electrical energy per cycle, M, plus the water heating energy consumption per cycle, W.

Energy Factor (EF) = 1 / M + W

This equation may vary based on dishwasher features such as water-heating boosters or truncated cycles. The greater the EF, the more efficient the dishwasher is.

The EF is the energy performance metric of both the federal standard and the ENERGY STAR qualified dishwasher program. The federal EnergyGuide label on dishwashers shows the annual energy consumption and cost. These figures use the energy factor, average cycles per year, and the average cost of energy to make the energy and cost estimates. The EF may not appear on the EnergyGuide label.

Test Criteria for ENERGY STAR Qualified Dishwashers

Dishwasher manufacturers must self-test their equipment according to the new Department of Energy (DOE) test procedure defined in 10 CFR 430, Subpart B, Appendix C. This DOE test procedure was announced on August 29, 2003, and all models had to be tested using the new procedure by February 25, 2004.

This test procedure establishes a separate test for soil-sensing machines. Included in the final rule was a decision to add standby energy consumption to the annual energy and cost calculation, but not to the energy factor calculation. Also, the average cycles per year has been lowered from 264 cycles per year to 215 cycles per year. Energy Star dishwashers are at least 25 percent more energy efficient than minimum federal government standards.

The table below lists the standard and the ENERGY STAR approved dishwasher energy factors.

Energy Standards for Dishwashers
Product Type Federal Standard Energy Factor ENERGY STAR Energy Factor
Standard ( > 8 place settings + six serving pieces) > 0.46 > 0.58
Compact (< 8 place settings + six serving pieces) > 0.62 NA

The current ENERGY STAR criteria for dishwashers became effective January 1, 2001. This criteria of at least 25 percent above the federal standard and applies only to models manufactured after January 1, 2001. The previous ENERGY STAR criterion was 13 percent above the federal standard.