I have looked into this, and found a really interesting magazine called 'Go Green and Save money' which had an article about dishwashers.
It is definatly saving more water to fill up a dishwasher and do one load, then to hand wash after each meal. Research has found that most modern dishwashers use as little as 10 litres of water per wash, which is up to six times less than the average person uses to wash the same amount in the sink. These figures ofcourse change when there is a much older, non energy efficient dishwasher in use.
Some simple steps that you can take to get the best use out of your dishwasher and to save water are:
-Make sure the dishwasher is completely full, because the dishwasher uses the exact same amount of energy to run a full load as it does a half load.
-Dont rinse your dishes before you put them in the dishwasher.(unless ofcourse they are really dirty and require a bit of a scrub) Independant tests demonstrate that there is little difference in the final levels of cleaning between pre-washed and un-washed dishes.
-Scrape of any larger chuncks of food off the dishes, or maybe give them a wipe with paper towl rather then water.
- Set your temperature of the cycle to 'low'
-Make sure you reguarily clean out your dishwashers filter. It helps your machine run at maximum efficiency, getting more dishes clean for less energy.
For a list of the most energy efficient dishwashers out there, go to http://www.energyrating.gov.au
Hope this has helped.