Microwave ovens cook or heat food and beverages by converting electricity to microwave radiation to heat water molecules within the substance.
DOE issued microwave test procedures for standby and off mode in January 2013 and the first-ever efficiency standards for microwave ovens in June 2013. The new standard specifies a maximum standby power of 1.0 watt for microwave-only ovens and countertop combination microwave ovens and 2.2 watts for built-in and over-the-range combination microwave ovens. According to DOE, the standard for microwaves sold over 30 years is estimated to save 0.48 quads of primary energy and to generate $1.5- $3.4 billion in net present value savings. The standard will take effect in 2016.
According to the 2009 Residential Energy Consumption Survey (RECS) by the EIA, about 95% of U.S. households own a microwave. DOE identified four technology options that could reduce electricity consumption in standby mode: 1) lower-power display options; 2) cooking sensors with no standby power requirement; 3) improved power supply and control board options; and, 4) automatic power-down. While conventional cooking sensors (which tell the microwave when to shut off during a cooking cycle) consume 1-2 watts in standby mode, multiple sensor technologies are available that consume zero standby power. Adding an automatic power-down element, which turns off most power-consuming components after a certain period of inactivity, could achieve standby power levels of less than 1 W.