As of August 11, 2009, ENERGY STAR qualified dishwashers are required to use 5.8 gallons of water per cycle or less. Older dishwashers use much more water than newer models. A dishwasher purchased before 1994 uses more than 10 additional gallons of water in each cycle compared to a new ENERGY STAR qualified model. Use the ENERGY STAR qualified dishwasher product search to learn the specific gallons of water per cycle for all ENERGY STAR qualified dishwasher.
If you want to save even more water: scrape don't rinse. Pre-rinsing dishes before loading the dishwashers can use up to 20 gallons of water. Just scrape food off the dishes and load. ENERGY STAR qualified dishwashers and today's detergents are designed to do the cleaning so you don't have to pre-rinse. If your dirty dishes are going to sit overnight, use your dishwasher's rinse feature. It uses a fraction of the water needed to hand rinse.
Also keep in mind, washing dishes by hand uses much more water than using a dishwashers. Using an ENERGY STAR qualified dishwashers instead of hand washing will save you annually 5,000 gallons of water, $40 in utility costs, and 230 hours of your time.