Dishwashers are one of the greatest kitchen conveniences. They themselves don't use that much energy. More than 80 percent of the energy used by a dishwasher is for heating the water they use, so most of the measures you apply to improving your hot water efficiency will benefit dishwashing energy efficiency as well, like lowering tank temperature. Dishwashers generally use between 8 and 14 gallons of water for a wash cycle. The range can be varied depending on which setting you select, from light rinse to pot-scrubber mode.
Some people keep their home's water heater temperature set at 140°F because their dishwasher requires this temperature to break down powdered dish soaps. However, most dishwashers have built-in heaters to boost water temperature up to 140°F to 145°F, the temperature range recommended by manufacturers for best dish washing performance. Having a booster heater allows you to turn your water heater thermostat down, which will reduce water heating costs.
Use your dishwasher's lightest wash setting that will do the job. Heavy duty or pot scrubber setting use more water and therefore cost more. And easy way to save money on the dishwasher is to use the “no-heat dry” option, then, open the door and let the dishes dry rather than allowing the electric heating element to come on. And try to only run the dishwasher when it has a full load.
When looking for a new dishwasher, look for the EnergyGuide label that tells how much electricity, in kilowatt-hours (kWh), the dishwasher will use in one year. But read carefully to be sure that the number of cycles and the normal settings are what you will use in a year. Also look for the EnergyStar logo indicating the dishwasher exceed federal standards by at least 13%.
Look for energy efficient features that will reduce hot water use and required settings like booster heaters and smart controls. Check to see how many gallons of water the dishwasher uses during different cycles. Dishwashers that use the least amount of water will cost the least to operate.