Dishwashers are the way to go if you comply with two simple criteria. Run a dishwasher only when its full, and dont rinse your dishes before putting them in the dishwasher. So says John Morril of the American Council for an Energy-Efficient Economy, who also advises not using the dry cycle. The water used in most dishwashers is hot enough, he says, to evaporate quickly if the door is left open after the wash and rinse cycles are complete.
Dishwashers More Efficient Than Hand Washing
Scientists at the University of Bonn [pdf] in Germany who studied the issue found that the dishwasher uses only half the energy, one-sixth of the water, and less soap than hand-washing an identical set of dirty dishes. Even the most sparing and careful washers could not beat the modern dishwasher. The study also found that dishwashers excelled in cleanliness over hand washing.
Most dishwashers manufactured since 1994 use seven to 10 gallons of water per cycle, while older machines use eight to 15 gallons. Newer designs have also improved dishwasher efficiency immensely. Hot water can now be heated in the dishwasher itself, not in the household hot water heater, where heat gets lost in transit. Dishwashers also heat only as much water as needed. A standard 24-inch-wide household dishwasher is designed to hold eight place settings, but some newer models will wash the same amount of dishes inside an 18-inch frame, using less water in the process. If you have an older, less-efficient machine, the Council recommends hand washing for the smaller jobs and saving the dishwasher for the dinner partys aftermath.
Energy-efficient Dishwashers Save Money
New dishwashers that meet strict energy and water-saving efficiency standards can qualify for an Energy Star label from the U.S. Environmental Protection Agency (EPA). Besides being more efficient and getting the dishes cleaner, qualifying newer models will save the average household about $25 per year in energy costs.
Like John Morril, the EPA recommends always running your dishwasher with a full load and avoiding the inefficient heat-dry, rinse-hold and pre-rinse features found on many recent models. Most of the appliances energy used goes to heat the water, and most models use just as much water for smaller loads as for larger ones. And propping the door open after the final rinse is quite adequate for drying the dishes when the washing is done.
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