Save money with the water heater built into your dishwasher The appliance that typically requires the hottest water in the house is the dishwasher at 140 degrees.  If your dishwasher has its own built-in heater – and most modern dishwashers do – you can reset the household water heater thermostat to 120 degrees.  Heat controls on water heaters are often inaccurate, so measure the temperature with a cooking thermometer and adjust the thermostat as necessary.  NOTE: This idea won’t work if you have a water heater that’s too small for your requirements.  Then it will pay to keep the water temperature higher, lowering it with cold water as needed for laundry, showers, and washing dishes.

Rely more on your dishwasher to save hot water
Not only do automatic dishwashers clean dishes and flatware more thoroughly than hand washing, they can save 6 or more gallons of hot water per load compared to washing the same dishes by hand.  If you run the dishwasher once a day, you can save the cost of heating more than 2,000 gallons of hot water a year.

Don’t rinse dishes before you put them in, just scrape them
Rinsing dishes before you put them in the dishwasher wastes water and the energy used to heat it.  New dishwashers clean better, eliminating the need for pre-rinsing unless food is baked or dried onto plates or pans.

Use your dishwasher’s energy saver feature or air-dry your dishes
Modern dishwashers allow you to turn off the heated drying cycle.  Doing so halves the energy used for a load of dishes.  If this energy-saving feature is absent, stop the machine during the cycle after the final rinse, and open the door partway to air-dry the dishes.

Run the dishwasher only when it’s full
A dishwasher consumes the same amount of energy to wash one dish as to wash a full load, so fill the dishwasher before running it.  However, do not overfill. Dishes stacked too close together shield each other from the water spray inside the dishwasher and are likely to remain soiled when the washer stops.