In my experience, dishwashers use more water, not less. Growing up, we used a dishwasher regularly, and the process looked like this:

a) remove all bits of food with regular washing, stack next to sink

b) transfer from next to sink to dishwasher

c) (after running dishwasher) wipe off hard water residue from all glass dishes

d) put away dishes

When I moved out on my own, I discovered the joy of a simple wooden dish rack next to your sink:

a) remove all bits of food (and oil) with regular washing, stack next to sink

And the above is all one has to do! The dishes dry naturally, and putting them back into the cabinet is optional. Notice almost identical step a). How am I supposed to believe dishwashers save water? We used twice the water simply to get rid of oil! After my partner got tired of wiping hard-water residue, we abandoned our dishwasher and never looked back.