It's easy to use a dishwasher efficiently. Be sure to scrape your plates into the Green Bin instead of rinsing them. Run full loads, and use the water/energy saving mode.
When buying a new dishwasher, think about buying a water-saving model. Energy Star dishwashers a use less than 16.1 litres of water per cycle.
Washing dishes by hand can use a lot of water if you leave the water running to rinse each item. Fill a sink with rinse water to prevent waste.