A dishwasher uses less water than washing dishes by hand—here's why

If you're trying to save water through washing dishes by hand instead of running the dishwasher, we're afraid you've got it backwards. Studies show that automatic dishwashers use far less water than human hands scrubbing with soap and water.

We wanted to see for ourselves, so we cooked up a test in which we cleaned dishes by hand and measured how much water we used. Then, we did the same thing with an automatic dishwasher.

The result? When you hand wash, you're using 3.5 times as much water as a dishwasher uses. That's not even counting the energy used to heat hot water, or the time you could spend doing something else.

Here's how the test went down

We started by dirtying four standard place settings with common, representative food stains like dried-on meat residue and baked-on cheese. Then, we picked two common detergents for loosening up the grease and grime: liquid Joy for hand washing, Cascade for the dishwasher.

We installed our top-rated dishwasher—the popular Bosch 800 Series—for Team Dishwasher, and set it to run on a Normal cycle. For Team Handwash, we used two Reviewed employees who have each lived in apartments without automatic dishwashers. One cleaned using a basin of soapy water, while the other left the water running during the scrubbing and sponging.

We attached flow meters to measure how much water the faucet and the dishwasher used. And we inspected the dishes afterwards to see how clean they got.

These are the results

When it comes to washing dishes, there's no contest: Hand washing uses far more water, even if you're not filling up the dishwasher.

In our tests, we found that it took just over 12 gallons of water to wash four place settings by hand. If your faucet isn't as efficient as ours—which is rated at one gallon of water flow per minute—you might use even more water.

Hand washing used 5 times as much water as an efficient dishwasher, and 3.5 times more water as an average dishwasher

By comparison, our dishwasher used just 2.36 gallons of water to get dishes just as clean. And it's not a hyper-efficient outlier, either. In fact, the last 10 dishwashers we tested used just 3.4 gallons per wash.

In other words, hand washing used 5 times as much water as an efficient dishwasher, and 3.5 times more water as an average dishwasher. The more dishes you wash by hand, the more water you waste.

You can save some water by soaking dishes in a bin instead of rinsing them with fresh water throughout the cleaning process. But the resulting dishes were still dirty after cleaning.

Consider a dishwasher over hand washing, even if you have limited space

You might assume that a dishwasher fills up to the top with water, or sprays a constant stream of fresh water. But you'd be entirely wrong.

Modern dishwashers use an elaborate setup of pumps, filters, and spray jets that reuse water throughout the cleaning process. Clean water is only used at the very beginning and on the final rinse. During the wash, water gets filtered and heated up for maximum cleaning.

And that brings us to our final reason why you should stop hand washing: Instead of scrubbing the remains of dinner off your plates, a dishwasher can do the work while you do something else.

If you don't have a dishwasher in your home or apartment, and there's nowhere to install one, consider a portable model. They hook up to a sink so you don't have to make major renovations. Here are our picks for the best portable dishwashers you can buy.