Answer: A new Energy Star qualified dishwasher uses 4 to 6 gallons of water per cycle, while other models can use from six to 16 gallons depending on the age and model.

More Info: As of August 2009, Energy Star qualified dishwashers must use 5.8 gallons of water per cycle or less. A dishwasher bought before 1994 uses around eight more gallons of water compared to a new Energy Star qualified model. Newer models often have the option to use a shorter cycle for less soiled dishes or can be set to skip the pre-rinsing stage.

Here are a few water-saving tips for the environmentally conscious dishwasher:

• Fill it up... but not too full. Unless you are in a rush to have clean dishes, wait until the dishwasher is filled up but still has enough space around the dishes for proper cleaning.
  
  
• Instead of rinsing your dishes before putting them in the dishwasher, just scrape off the bigger scraps and let the washer do the rest. Some models even have a pre-rinse that uses far less water than by-hand rinsing if you are worried about hard-to-clean dishes.
  
  
• Saving energy is good too. Since the main energy cost when using a dishwasher is in heating the water, which is also needed when washing by hand, the more water-efficient your dishwasher is, the more energy it conserves. Consider letting dishes air-dry over night to save even more on that electric bill instead of using the dishwasher's drying cycle.