Inefficient High-Efficiency Electric Water Heaters

High-efficiency electric water heaters with stated energy factors (EFs) of .93 or .94 may not be living up to their ratings.

High-efficiency electric water heaters may not be living up to their ratings. The Department of Energy (DOE) is investigating whether the energy factors (EFs) of .93 or .94 that some water heater manufacturers claim for certain models are accurate, or whether the real EF rating may be closer to .89. At a recent workshop on water heater energy conservation standards, DOE, the Oregon Department of Energy, and others questioned how 50-gallon electric water heaters could achieve EFs of .93 or higher when available data and DOE's engineering analysis indicate that EFs this high aren't achievable with current designs.

It is possible that the misreported ratings may be a result of manufacturers' failure to follow DOE certification regulations. These regulations require manufacturers to base their ratings on the results of tests run on two or more water heaters. DOE has asked water heater manufacturers for information to verify their ratings.

Consumers who purchase electric water heaters that are rated at .93, but have an actual EF of .89, will pay more in operating costs. The .04 EF difference can increase electric costs by roughly $10 annually, or $150 over the expected life of the appliance, depending on local electricity rates. While this increase may not amount to much on an individual basis, about 800,000 high-efficiency water heaters are sold annually, which translates to a potential $8,000,000 of unexpected electricity bills each year.

The problem of misreported ratings may have begun in the early '90s. One possible reason that manufacturers might overstate a water heater's EF would be to qualify for utility rebate programs. Several utilities have run rebate programs to subsidize the purchase of water heaters with an EF greater than .90. The programs rebated to the consumer as much as $150 to pay for more efficient water heaters. Water heaters that should have received an EF rating of .89 would not qualify for these rebate programs.

Traditionally, DOE has relied on self-certification by appliance manufacturers and has been remarkably successful in achieving compliance. As evidence of the success of self-certification, one expert noted that he had tested many refrigerators over the years and had found that the manufacturers typically overstated consumption. It remains to be seen whether water heater manufacturers may have spoiled this excellent record.

--Mary James

Mary James is the editor/publisher of Home Energy.

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