Did you know that the average faucet flows at 2 gallons per minute? So if you can successfully wash and rinse eight place settings (plates, bowls, forks, knives, spoons, glasses, etc.) and about six serving dishes that your dishwasher can handle without running the faucet for more than 2 total minutes, then, you might be better off hand-washing. Assuming you’re washing 54 pieces of dishware (that’s 48 pieces of dishware, 6 pieces per setting, and 6 serving dishes), you’ve got about 4.4 seconds of wide-open tap water per piece, or about 9.5 ounces of water to wash and rinse each dish. The average dishwasher uses 6 gallons of water per cycle; the average Energy Star-rated dishwasher uses 4 gallons per cycle.
Although it is possible to be more efficient when hand-washing, it’s actually pretty tough. Can you successfully wash and rinse a soiled dinner plate in just over a cup of water? If you can keep the water use low, equal to an efficient machine, you’ll require less energy. However, doing an entire load of dishes in 4 gallons of water is roughly equal to doing them all in the same amount of water you use in 96 seconds of showering (using a showerhead that releases 2.5 gallons per minute).
So, as long as you don’t often run your dishwasher when it’s only half full of dirty dishes, run during peak hours (try running your dishwasher during off- peak hours- bedtime), or unless you are very miserly with your water use (or have an old, inefficient dishwasher), the automatic dishwasher is likely to be more efficient.
It’s better to pay a small price today than it is to pay a bigger price tomorrow.