DOE cooking up energy savings for ranges and ovens

Today, the US Department of Energy (DOE) issued a proposed rule for new standards for residential cooking products. The proposed standards are based on straightforward measures that would significantly reduce energy waste while maintaining all the features available to consumers today. In particular the proposed standards would cut standby power consumption.

Background

Today’s proposed rule addresses electric and gas cooking tops and ovens. (A range includes both a cooking top and an oven.) The current standard for gas cooking products is a prescriptive requirement which prohibits standing pilot lights. There are currently no efficiency requirements for electric cooking products.

Last year, DOE proposed standards for residential ovens. At that time, DOE did not propose standards for cooking tops because the agency was still working on a test procedure that could be used to test all cooking tops including induction products. In response to the 2015 proposed rule, DOE received comments from manufacturers raising the concern that “commercial-style” gas cooking tops and ovens have features (e.g. cast iron grates, heavier racks, thicker oven walls) that make them less efficient than conventional residential-style products. In response to these manufacturer comments, DOE recently proposed to repeal the test procedure for ovens and is now proposing a new approach for oven standards. DOE has also now developed a test procedure that can be used for all electric and gas cooking tops and is the basis for today's proposed standards for cooking tops.

Cooking tops

There are three general types of cooking tops: electric coil, electric smooth, and gas cooking tops. The proposed standards for electric coil cooking tops are based on improving the design (flatness) of the coil heating element. For electric smooth cooking tops, the proposed standards are based on improving the efficiency of the power supplies used to power the electronic controls and implementing an auto power down feature to power down the controls after a period of user inactivity. Both of these measures can significantly reduce the standby power consumption of electric smooth cooking tops. Finally, for gas cooking tops, the proposed standards are based on optimizing the burner and improving the grate design. DOE selected the efficiency level for gas cooking tops such that it can be met by commercial-style units including units with cast iron grates and multiple burners with high input rates.

Ovens

For ovens, DOE is proposing prescriptive requirements that would improve the efficiency of the power supplies and ignition systems used with ovens. Both electric and gas ovens would be prohibited from using a linear power supply. Switching from a linear power supply to a switch-mode power supply can significantly reduce standby power consumption. DOE found that multiple manufacturers are already transitioning to this option for their full product offerings. Switch-mode power supplies are also widely used in electronics such as cell phones, laptops, and digital cameras.

In addition to using a more-efficient power supply, gas ovens would also be required to use an improved type of ignition system to further reduce energy waste. Many gas ovens on the market today use a type of ignition system called a glo-bar (or hot surface) igniter. The problem with typical glo-bar ignition systems is that they remain energized throughout the period of burner operation, and DOE found that they consume about 300-450 watts (W). With the proposed prescriptive requirement, gas ovens could use one of two general types of more efficient ignition systems: (1) an intermittent/interrupted ignition system, where the ignition source is turned off after the main burner flame is ignited, such as an electronic spark ignition system, or (2) an intermittent pilot ignition system, where a spark lights a pilot flame to ignite the main burner and the pilot shuts off when the main burner shuts off, such as a battery-powered ignition system.

DOE found that multiple types of ignition systems meeting the proposed requirement are available in current products, and the proposed prescriptive requirements for gas ovens would allow for maintaining the features available in ovens marketed as commercial-style.

Savings from the proposed standards and next steps

DOE estimates that the proposed standards would save 760 trillion British thermal units (BTUs) of energy over 30 years of sales, which is equivalent to the annual energy consumption of more than 4 million US households. The net savings to consumers over the same time period would be $2.7-6.2 billion.

DOE is scheduled to finalize new standards for cooking products by the end of this year, and the standards would take effect 3 years after publication of the final rule.