The very first water-pressure dishwasher, patented in 1885, was invented by American socialite Josephine Cochran after she got tired of cleaning fine china by hand herself.
And who can blame her? Judged purely by the time we save on this chore, a dishwasher beats handwashing any day.
But there’s another debate happening in homes everywhere—and it’s not just who gets dish duty tonight. Since we’re all looking for ways to conserve water in the kitchen, the question becomes: is it more environmentally friendly to handwash our messy dinnerware or pop it into the dishwashing machine?
Cleaning dishes in an average American home takes anywhere from 6 to 27 gallons of water per load.
This decision matters.
How many gallons of water does it take to wash your dishes?
Cleaning dishes in an average American home takes anywhere from 6 to 27 gallons of water per load, according to estimates by the U.S. Geological Survey’s Water Science School.
It’s typically a daily task, too, so those gallons add up fast. Since it’s not obvious whether dishwashers save water versus hand washing, we rolled up our sleeves and dove into the research to see which method is best for an energy-efficient homes.
3 factors to consider when evaluating whether a dishwasher or hand washing uses more water
The difference between 6 and 27 gallons is pretty massive.
It may be tempting to assume handwashing is the less water-intensive option, while the dishwasher automatically lands on the higher end of this eco-spectrum. But the murky truth is: It depends.
1. Whether you have an energy-efficient and water-efficient dishwasher
First, it depends on the dishwasher. If you’ve had the same old appliance since before the fall of the Berlin Wall (circa 1989), it could be gobbling up as much as 16 gallons of water per typical cycle, not including the under-the-tap pre-rinse (more on that later).
In the mid-1990s, however, the EPA’s Energy Star program, launched to promote energy-efficient appliances and help consumers make better choices, was expanded to cover the dishwasher category.
How much water does an energy-efficient dishwasher use?
Some of the newest Energy Star models use as little as 2.36 gallons of water per cycle.
Today, choosing an Energy Star–certified dishwasher means it’s on average 12 percent more energy-efficient and 30 percent more water-efficient than a non-certified model. Some of the newest Energy Star models with clever eco-wash options use as little as 2.36 gallons of water per cycle.
Of course, there are more factors to consider than just water.
Unlike your arms, a dishwasher requires electricity—enough to heat the water (which you’d need for handwashing, too) and run the machine. The amount required, as it turns out, is relatively small.
How much CO2 does a dishwasher produce?
Let’s say your Energy Star appliance uses 4 gallons and 0.87 to 1.59 kWh per load. Using the EPA’s Greenhouse Gas Equivalencies Calculator, that works out to 1.4 to 2.5 pounds of CO2 per load. (For perspective, you probably exhale more carbon dioxide than that each day.)
IfOnce you factor in all of these water-wasting inefficiencies, it’s very likely that washing by hand is likely the more eco-friendly choice.
2. How efficiently you use your dishwasher
There’s another factor even the most diligent environmental scientist can’t measure: you. Or, more specifically, your potentially imperfect kitchen habits.
Do you run the machine half full? (Multiply all those numbers above by two, of course.) Do you run it on super-intense-extra-filthy-mode-plus-heat-dry when a quick cycle would do just fine? Do you leave the tap running while rinsing every plate as you load? (Oops.)
Once you factor in all those extras, you might be wondering, wouldn’t it be better to just do them in the sink the old-fashioned way?
3. Whether you use the two-basin method to hand wash your dishes
When washing by hand, there are plenty of ways to save water: avoid running taps, opt for scraping food residue over pre-rinsing. Most importantly though, is to follow the two-basin (or two-sink) method.
What is the double sink method?
The double sink method is when you fill one sink with hot soapy water; dirty dishes stay there for soaking and scrubbing. Sink two uses cool water for rinsing off, before a towel- or air-dry. Both drains stay plugged the whole time.
Dishwasher vs. handwashing: the verdict and best ways to save water
One study that looked at real-life dishwashing habits in homes across four countries (Germany, Italy, Sweden and the UK) found that households with a dishwasher used on average 50 percent less water and 28 percent less energy per cleaned item, compared with dishwasher-free households.
Another recent study published in the journal Environmental Research Communications also found that, on average, dishwashers save more water and also produce less greenhouse gases. (Full disclosure: This study was partially funded by Whirlpool.)
In this second study, they calculated that “typical manual washing” would, over the course of 10 years, equal 34,200 gallons of water going down the drain; a dishwasher in the same time would use 16,300 gallons.
In terms of greenhouse gases (related to heating water), typical handwashing produced 5,620 kilograms of CO2e over a decade compared to the dishwasher’s 2,090, based on washing four loads a week.
To be fair, the researchers’ definition of typical manual washing involved leaving the tap running the whole time—a convenient method that, admittedly, is probably quite common. They point out that washing by hand “has the potential to have the lowest GHG emissions”—if it’s done right.
That said, a properly executed two-basin routine is the most climate-friendly pick overall (when judged by lifecycle GHG emissions, since handwashing doesn’t require an appliance to be manufactured), but if you already have a dishwasher, particularly an efficient one, the machine might in fact be the more water-saving choice.
What’s the best way to wash dishes without wasting water?
As we’ve just seen, the difference when it comes to lowering carbon emissions (and your impact on climate change) isn’t black and white—the simple goal is to use as little energy and hot water as possible.
Whether you wash your dishes by hand or use a dishwasher, there are ways you can further reduce your water consumption to help reduce your impact on the environment.
1. Use the two-basin method when washing by hand
Not all of us have the luxury of passing dish duty over to a machine, or maybe you just have delicate dinnerware and cookware that need to be treated with extra care and washed by hand.
If that’s the case, then the best way to reduce your water usage is to stick with hand washing and to use the two-basin method.
2. Use full loads and skip the pre-rinse when using a dishwasher
Many people feel like they should pre-rinse dishes before putting them in the dishwasher. But it turns out that by skipping the pre-rinse and using a full load, you can significantly save on water and energy consumption.
3. Upgrade to an energy-efficient dishwasher when the time is right
When the time comes to replace your clunky, outdated machine, pick the most energy-efficient, modern model you can.
New washers have advanced technologies like soil sensors to adjust the cycle’s length, filtration systems to use and reuse the same water, and efficient jets that do more with less energy.
So you can just give your messy plates a scrape instead of rinsing, and let the dishwasher do the rest of the dirty work.
It truly can be a helping hand in our energy-efficient home.
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