不要把你的碗洗手!| HowStuffWorks

"The Bob," a mini-dishwasher and ultraviolet sterilizer, is presented at the Internationale Funkausstellung IFA international trade show for consumer electronics and home appliances on Sept. 3, 2020, in Berlin.TOBIAS SCHWARZ/AFP via Getty Images

The list of historic face-offs is long and storied.Batmanversus Superman. Kong versusGodzilla. Dishwashing versus hand-washing? OK, maybe the last isn't quite as action-packed as the others, but people still have strong opinions about who should win.

Many people hand-wash dishes when there's a perfectly gooddishwasheravailable. Often, this is because the modern convenience seem optional and wasteful. After all, dishwashers require lots of water and energy to run, right? So why not just DIY and feel good about yourself in the process?

Relax. This is one time when the easier alternative is actually the better one.

"There's a common misconception that the dishwasher fills up with water, so many people choose to wash dishes by hand instead of using the dishwasher because they believe it's more efficient," saysJill Franke, a senior scientist at Cascade (the automatic dishwasher detergent) in an email. "The reality is, according toENERGY STAR、认证洗碗机使用小于4加仑(15 liters] of water per cycle compared to hand-washing, which can use 4 gallons of water every two minutes."

You might not be surprised to see Cascade give a thumbs-up to dishwashers. But theNatural Resources Defense Council (NRDC)agrees.

"Today's dishwashers do a great job cleaning your dishes and only use 3 to 5 gallons [11 to 19 liters] of water to clean an entire load," says Noah Horowitz, senior scientist with the NRDC in an email.

Much of this energy-saving is thanks to advances made in dishwasher technology over the last decade. A standard ENERGY STAR certified dishwasher saves anaverage of 3,870 gallons(14,650 liters) of water over its lifetime. Plus, it only costs an average of $35 per year to operate.

This is despite relatively new regulations on faucet efficiency. "Per federal standards, new kitchen faucets may not use more than 2.2 gallons [8.3 liters] per minute. Efficient faucets only use around 1.5 gallons [5.6 liters] per minute," says Horowitz. "Even if you are super-fast, there is no way you can wash the equivalent of a dishwasher full of dirty dishes in under three minutes. If you leave the water running while washing your dishes you could easily consume over 20 gallons [26 liters] of water to clean the day's dishes."

So, 20+ gallons while hand-washing vs. 4 (or less) using the dishwasher? That's a pretty significant difference.

But, what about the related energy costs? Turns out the dishwasher is another clear winner there, too. "The dishwasher is actually far more energy-efficient than the sink, which uses energy throughout the dishwashing process to heat water," Franke explains. "In fact, the dishwasher is so much more energy-efficient that if you switch from handwashing to running your dishwasher just four times a week, you can save up to $130 a year on your energy bill – even if you have an older dishwasher!" (She adds that this figure assumes an electricity rate of 11 cents per kilowatt-hour.)

Using the Dishwasher Efficiently

So, now that we've seen that the dishwasher beats hand-washing, here are a few ways to save even more water and energy when using the appliance.

Fill 'er up.When possible, fill up the dishwasher completely before turning it on. This allows it to be the most efficient with your water.
Scrape. "Scraping off left-over foods from dishware allows the dishwasher to run more efficient cycles and consume less water within the overall consumption range," emails Chris Baum, director of dish care with Electrolux Major Appliances.
But resist the prerinse."You should trust your dishwasher to get those dishes clean, so you shouldn't need to spend the extra water to do a lot of prerinsing before you put the dishes in the dishwasher," Baum adds. Horowitz concurs that prerinsing your dishes is "a total waste of water and energy."
Upgrade.If your dishwasher is very old, buying a new energy-efficient one can save you money in the long run. Older model dishwashers use an average of10 to 15 gallons (38 to 57 liters) of waterper load. When shopping, "Look for one that has the blue ENERGY STAR label on it, which means it's an energy- and water-efficient model," Horowitz suggests.

If you must wash dishes by hand, the most efficient way to do it is to fill the sink up with hot, soapy water. Allow the dishes to soak, then rinse them off in another sink full of hot water (with no soap). Resist the urge to leave the sink running the whole time, as this is when massive amounts of water literally go down the drain.