Most energy used by a dishwasher is for heating water; therefore, loading a dishwasher fully and properly before operating it can save energy. Overloading can lead to ineffective cleaning that can require rewashing, and half-empty loads can require operating the dishwasher twice as often.
Many dishwashers contain a built-in booster heater to raise the temperature of water entering the unit to 140 degrees Fahrenheit to ensure optimal cleaning. If a dishwasher has this feature, a water heater’s setting can be lowered to 120 degrees Fahrenheit, which is sufficient for other uses in the home. Up to 13 percent can be saved on a total water-heating bill for every 10 degrees Fahrenheit the water heating setting is lowered. No matter the type of dishwasher, the rinse hold setting will use an additional 3 to 7 gallons of hot water, which is especially inefficient when washing only a few dishes.
Air drying dishes saves energy. If there is no air dry setting, turn off the control knob after the final rinse and open the door slightly to facilitate drying. For best air-drying results, run the dishwasher in the evening and let dishes dry overnight before unloading.
If purchasing a dishwasher, look for an ENERGY STAR®-qualified model. ENERGY STAR-qualified dishwashers use at least 25 percent less energy than currently available standard models. They save energy by using less water than standard dishwashers; therefore, less water-heating energy is required. They also reduce water consumption, so water and sewer bills are lower. If a dishwasher is more than 10 years old, approximately 1,000 gallons of water per year can be saved with a new ENERGY STAR-qualified model.