As with the Clothes Washer, the Dish Washer uses hot water and that is the big cost. Our house is super insulated and the water is solar heated so we save a lot more money then the normal home owner. The experts say:

http://www.energystar.gov/index.cfm?c=dishwash.pr_dishwashers

 Dishwashers

Replacing a dishwasher manufactured before 1994 with an ENERGY STAR qualified dishwasher can save you more than $30 a year in utility costs.

 Earning the ENERGY STAR means a product meets strict energy efficiency guidelines set by the US Environmental Protection Agency and the US Department of Energy.

• ENERGY STAR qualified dishwashers use at least 41 percent less energy than the federal minimum standard for energy consumption.
• ENERGY STAR qualified dishwashers use much less water than conventional models. Saving water helps protect our nation’s water supplies.
• Because they use less hot water compared to new conventional models, an ENERGY STAR qualified dishwasher saves about $90 over its lifetime.

Remember, saving energy prevents pollution. By choosing ENERGY STAR, you are helping prevent global warming and promote cleaner air without sacrificing the product quality and performance you expect.

You may also be interested to know that you can save extra energy while washing dishes, whether with a standard or an ENERGY STAR model:

• Run your dishwasher with a full load. Most of the energy used by a dishwasher goes to heat water. Since you can’t decrease the amount of water used per cycle, fill your dishwasher to get the most from the energy used to run it.
• Avoid using the heat-dry, rinse-hold and pre-rinse features. Instead use your dishwasher’s air-dry option.

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More over: 

http://www.aceee.org/consumerguide/dishwashing.htm

To find the most efficient products, download a list of qualifying products from the ENERGY STAR Web site (link to excel file in the upper-right). Sort by “Size” and “Energy Factor” to see which meet our recommendations (below). You may need to also check product literature or with your utility for further specifications. For a quick search by manufacturer, here’s a direct link to the list in html.

When buying a new dishwasher, consider the following:

1. High Energy Factor
ACEEE recommends that you consider dishwashers that have an Energy Factor (EF) of at least 0.65, or an estimated energy use of less than 340 kWh/year. This is about 40% better than the federal standard. You can find which products meet this requirement on the showroom floor by looking on the yellow EnergyGuide label on each product.

Energy Factor measures the number of cycles that can be run with 1 kWh of electricity, and, unlike clothes washer efficiency ratings, does not take into account water use; although high-efficiency models are more likely to incorporate improvements to the spray arm, sump geometry, and/or pump design to reduce water requirements per cycle.

2. Low Water Use
To find the most water-efficient models, you must look beyond ENERGY STAR and EnergyGuide. Some ENERGY STAR models use half as much water as others, saving hundreds of gallons of water each year. Check the manufacturer’s literature or contact your local water utility. In some states, electric and water utilities offer rebates for the purchase of models that are exceptionally efficient.

3. Wash Cycle Options
Most dishwashers have several different wash cycle selections. The more options you have, the better you can tailor the energy and water use needed for a particular load. Look at the manufacturer’s literature for total water use with different cycles.Some dishwashers on the market today use “soil sensor” technology to automatically adjust water use depending on how dirty the dishes are in each load. There are highly-efficient dishwashers with and without this feature.4. Energy-Saving “No-Heat” Dry
An electric heating element is generally used to dry dishes at the end of the final rinse cycle, consuming about 7% of dishwasher energy use. Most new dishwashers offer an energy-saving no-heat drying feature. At the end of the rinse cycle, if the feature is selected, room air is circulated through the dishwasher by fans, rather than using an electric heating element to bake the dishes dry.

Whether you are buying a new dishwasher or using an existing one, you may be able to save a considerable amount of energy by changing the way you operate it.

• Avoid Hand-Washing
  Studies are showing more and more that, when used to maximize energy-saving features, modern dishwashers can outperform all but the most frugal hand washers.

• Scrape, Don’t Rinse
  Studies show that most people pre-rinse dishes before loading them into the dishwasher, even though dishwashers purchased within the last 5–10 years do a superb job of cleaning even heavily soiled dishes. If you find you must rinse dishes first, get in the habit of using cold water.

• Follow Manufacturer Instructions
  Completely fill the racks to optimize water and energy use, but allow proper water circulation for adequate cleaning.

• Wash Only Full Loads
  The dishwasher uses the same amount of water whether it’s half-full or completely full, so nothing will save more energy than waiting to run your dishwasher. If you find that it takes a day or two to get a full load, use the rinse and hold feature common on newer models. This will prevent build up of dried-on food while saving time and water compared to pre-rinsing each item. The rinse feature typically uses only 1 to 2 gallons of water.

• Use Energy-Saving Cycle Options
  Pay attention to the cycle options on your dishwasher and select the cycle that requires the least amount of energy for the job. Use the no-heat air-dry feature on your dishwasher if it has one.

• Turn Down the Water Heater Temperature
  Since the early 1990s, most dishwashers in the U.S. have been sold with built-in heaters to boost water temperature to 140–145°F, the temperature recommended by manufacturers for optimum dishwashing performance. The advantage to the booster heater is that you can turn down your water heater thermostat to 120°F (typically half-way between the “medium” and “low” settings

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AND The Winners Are:

http://products.pricerunner.com/results/query?q=energy+efficient+dishwashers