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Automatic dishwashers are convenient but maybe the least essential household appliance. You could wash by hand, after all -- and some misguided energy-savers think that's the environmentally friendly approach. They're wrong. Modern dishwashers are the most efficient way to clean up after meals, and one of the most energy efficient and least costly appliances in the home.
Many modern dishwashers use only half as much water as you would washing by hand, according to the Association of Home Appliance Manufacturers. That can add up to thousands of gallons over the appliance lifespan -- about 11 years for most dishwashers. And the automatic part also saves you about four hours a week of boring and repetitive cleanup.
Because almost all dishwashers have booster heaters, you can usually reap further savings by reducing the temperature setting on your household water heater. It doesn't need to be set at a sanitizing and potentially scalding 140-plus degrees, and a setting of 110 to 120 degrees should be adequate for other uses.
As to overall efficiency, products made by U.S. manufacturers generally lag behind the imports. While about 80 percent of dishwasher sales are for well-known brands (General Electric, Kenmore, KitchenAid, Maytag, and Whirlpool), the most efficient models are not exactly household names. AHAM reports that Asko, Bosch, Haier, Ultraline, and Fisher & Paykel offer models that use at least 80 percent less energy than required under federal law -- and cost under $26 a year to run. At the top end, some Asko and Bosch models cost only $19 a year to operate. That's based on an electric rate of 10 cents per kilowatt hour, the average national price in 2006, and includes the electricity used to heat the water and the electricity used directly by the dishwasher.
Another way to shop: Look for the Energy Star label. All standard-size Energy Star dishwashers (foreign and domestic) have average annual energy costs no higher than about $35. European models often are a little smaller than typical American machines. But you can select "standard" size on the Web site (energystar.gov), which means the machines have enough capacity to handle at least eight place settings and six serving pieces.
And on most new models there's no need to waste time and water by pre-rinsing because built-in soil sensors detect just how much washing the dishes need. Once in a while, you can splurge and run a top-rated dishwasher with a partial load -- a no-no on most energy-saving tip lists. But some models even adjust cleaning to the amount of dishes you're washing.
A full-load cycle, selected automatically, is rated for 12-place settings, and provides an even distribution of water through three spray arms. But a zoned machine allows you to wash small loads using only the upper or lower baskets. (You do have to pack the smaller load in the right places.) The partial-load setting reduces water consumption by up to 20 percent and energy consumption by up to 10 percent. Some manufacturers, such as KitchenAid, provide customizeable racks that let you tailor the machine from light to heavy loads.
One practical feature for many households is a time-delay start. In the increasing number of households that pay different electric rates at different times of day, a delayed start lets you run the dishwasher at off-peak hours when rates are lowest. In older homes where running one water-using appliance causes pressure and temperature fluctuations in another, deferring the dishwashing can eliminate some unpleasant surprises, say, when you're in the shower. Or it just may be convenient (and more quiet) to hit the three-hour or six-hour delay button so the machine churns when your somewhere else.
To smother the sound, most modern machines have quiet-running motors, vibration-damped mounts on the motor and pumps -- a simple matter of some extra rubber washers -- and extra insulation. Together, these improvements reduce noise by about half compared to models produced 10 years ago. If sound output is crucial, check into insulation levels when you comparison shop. But even average-quality machines today are so quiet that only some manufacturers list noise ratings -- in decibels (actual noise) or sones (perceived sound).
Several manufacturers, however, offer increasing levels of quietness in more expensive machines. KitchenAid, for example, follows the old Sears' marketing slogan of good-better-best, and offers Whisper Quiet, Whisper Quiet Plus, and, one supposes, the nearly silent Whisper Quiet Ultima.