Dishwashers actually use less water than hand-washing.
You'll save even more if you don't pre-rinse the dishes before loading them. The key to getting dishes clean is using very hot water. Some dishwashers have a device that raises the temperature of the water coming out of your water heater. Another feature you'll like is a built-in food disposer. It grinds up food particles and flushes them out with the waste water.