Run your dishwasher only with a full load. Use the energy saving modes when available. Don’t use heat when drying your dishes.
In the dishwasher versus hand washing debate, using an automatic dishwasher to clean dishes generally wins for both water and energy efficiency.
Most conventional dishwashers installed in U.S. households today use 7-14 gallons per load and account for less than 2 percent of the water used in an average American home. Despite the small portion of overall water consumption by dishwashers, newer machines are substantially more water-efficient than older models. Today the most efficient (full-size) machines use a maximum of 7 gallons per load – and some as little as 4.5 gallons.
Energy savings also result from upgrading to an efficient dishwasher because fewer gallons of water need to be heated per cycle.
Excerpt from the Portland Water Bureau’s Dishwasher Fact Sheet