The basic line is that from an environmental perspective, these machines have grown so energy- and water-efficient — especially Energy Star-certified models — that it is very hard to beat them through hand-washing (though, of course, you should first scrape off any food before putting dishes in the dishwasher, and you should run only full dishwasher loads).
The reasons for this are multiple, but they include the fact that dishwashers just keep needing less and less water (and energy) because of improving appliance standards, even as they get better and better at using it.
“While it may be possible to use less water/energy by washing dishes by hand, it is extremely unlikely,” Jonah Schein, technical coordinator for homes and buildings in the EPA’s WaterSense program, said in a statement. Schein was referring, in particular, to Energy Star-certified dishwashers, not all dishwashers.
“In order to wash the same amount of dishes that can fit in a single load of a full size dishwasher and use less water, you would need to be able to wash eight full place settings and still limit the total amount of time that the faucet was running to less than two minutes,” he said.
“Studies are showing more and more that, when used to maximize energy-saving features, modern dishwashers can outperform all but the most frugal hand washers,” adds the American Council for an Energy-Efficient Economy.
How well modern dishwashers conserve water and energy is not the same thing as how well they perform their cleaning task. And determining how clean is “clean enough” is somewhat subjective. But here, too, the machines have a number of advantages.
Modern dishwashers also often include an increasing number of high-tech features that are just better at cleaning than we are — the design of the racks, the spray of the water jets and other aspects have been tailored to improve performance.
The overall story here is a familiar one in the appliance world, and much like what has happened with refrigerators: Ever increasing standards have made dishwashers more and more energy- and water-efficient, even as they’ve also taken on new features, such as soil sensors, which detect whether your dishes are still dirty.
For instance, here’s a figure from a 2013 report by the American Council for an Energy Efficient Economy and the Appliance Standards Awareness Project, showing how dishwashers have become more energy- and water-efficient over time — and, simultaneously, cheaper to operate:
And that only runs through the 2010 standard. Yet another federal standard kicked in in 2013, requiring an additional 15 percent drop in energy use and 20 percent reduction in water use, according to the Energy Department.
Moreover, these are just the baseline standards. Highly efficient, Energy Star-certified machines use even less energy and water. They must use less than 4.25 gallons of water for each cycle, the Energy Department says.
Energy Star, too, keeps upping its game, with a new specification set to go into effect in January, whereupon a dishwasher that is Energy Star-certified “will use 12 percent less energy and 25 percent less water than a dishwasher that meets the federal minimum,” according to Melissa Fiffer, an Energy Star appliance product manager.
To compete with this by washing dishes by hand, you’d probably have to use a relatively small amount of water that is held in the sink with the drain plugged. And soak and scrub. Then you might come close or even outperform the machine — but as the quotation from the EPA’s Schein above indicates, it’s pretty hard to pull off.
And, of course, pre-washing dishes before throwing them in the machine in effect consumes water and energy twice (unless you use cold water, that is).
The worst approach for the environment — and energy and water bills — is pre-washing dishes in constantly running hot water and then running them in an ancient dishwasher that was not built to modern standards.
So then why do so many of us still believe in pre-washing our dishes?
The case seems analogous to one involving another largely outdated energy-related practice that still persists: idling your car for long periods to get the engine warm. That practice hails from the era of the carburetor, which has long since been replaced by electronic fuel injection.
Something similar could be said of the practice of pre-washing dishes.
“Old dishwashers, to generalize, didn’t get dishes very clean unless you pre-washed,” says Steven Nadel, executive director of the American Council for an Energy Efficient Economy. “The new dishwashers, that is not an issue. Almost all of them have what’s called soil sensors. Depending on how dirty the dishes are, they will wash more or less. They will get the dishes clean.”
Meanwhile, some dishwashers also have a “no heat air dry” feature, Fiffer explains. This saves even more energy.
“Clean dishes in a dishwasher will dry without added heat, although it may take longer,” she says. “Many dishwashers offer an energy-saving ‘no heat’ dry option, where the dishwashers use a fan to circulate air. Opening the dishwasher shortly after the cycle ends also helps dishes dry.”
But maybe none of this convinces you. Maybe water and energy aren’t precious to you, but even so, something else probably is — time.
The Energy Star program calculates that using one of its dishwashers — rather than hand-washing — also saves 230 hours, or nearly 10 days, per year. So, in sum, all ye eaters of food and washers of dishes: It’s probably time to give in, and let the machine win.
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