Does a dishwasher use a lot of electricity?

It depends. Not all dishwashers use the same amount of electricity. You can get a more accurate idea by locating the manufacturer's date plate or sticker, usually affixed to the door jamb of your appliance. It will show voltage and current used, It will show something like, motor 1 A heat 9 A. That means when just the motor is operating it's about 1 amp and when the heating elements come on the total will be 10 amps.

Look up US Department of energy stats, it will tell you average wattage that appliances uses, as well as the cost to use them.