The Great Dishwasher Debate

As a baseline, remember that water flows out of your tap at a rate of anywhere from three to five gallons per minute. New Energy Star-qualified dishwashers use as few as 3 gallons of water and 1 kilowatt hour of energy per load. New machines not only use less water and energy, but they're also better at cleaning your dishes and manufacturers recommend against pre-washing dishes before running the machine. The numbers are higher than you might expect: Rinsing dishes before loading the washer can waste up to 20 gallons of water, while the machine's rinse cycle only requires 1 to 2 gallons. But if you must rinse your dishes beforehand, use cold water instead of hot.

Washing by hand is the runner-up in energy and water use, provided that the hand-washer uses efficient techniques. Installing an aerator in your faucet can save you 3 to 4 gallons per minute of running your tap. Scraping food off, soaking dishes in a bin of soapy water before getting started, and not letting the water run while you wash every dish are some of the best ways to save water and energy. And it's best to have two dishwashing basins to work in—one filled with hot soapy water, the other with warm water for a rinse.

Coming in third is using an older machine. Depending on how long you've had it, your dishwasher could use anywhere from 8 to 15 gallons per load and up to three times as much energy as a new machine. Still, running a full load is the best way to get the most out of your machine, since it will use the same amount of water and heat whether it's washing one saucer or a dinner party's worth. Skip the dry cycle and let your dishes air dry. Running your dishwasher at off-peak hours will decrease the overall demand on your electricity provider.

And finally, regular washing by hand can use a whopping 27 gallons of water and 2.5 kWh of electricity if you let the water run.

If you haven't replaced your dishwasher in over a decade, you may want to think about switching to a newer model. You'll get a return on your investment in a new machine: If your dishwasher is at least 10 years old, you can save between $25 and $35 a year on your energy bill and save 1,056 gallons of water by replacing it with an Energy Star model. Assuming a 12-year machine life span, that's $400 in savings! Check out the Energy Star website's list of models.

One of the advantages of energy efficient machines is that they use less hot water and have soil sensors to adjust the length of a wash cycle and water temperature depending on how dirty your plates are. That way, your dishwasher won't waste energy cleaning dishes more than they need to be cleaned. If your machine has a "light wash" or "energy-saving" mode, that's another way to save on water and power.

If you're debating between a compact-capacity and standard-capacity dishwasher, think about your usage habits. While compact-capacity washers appear more energy efficient, go for the standard machine if it means you'll only have to run it once a day instead of multiple times.

Finally—and this applies to dishwashers and hand-washers—find a brand of detergent that does not contain phosphates or chlorine. Those cleaning agents can damage the environment and encourage the growth of harmful algal blooms once they enter the water supply. Phosphate-free detergent, such as Seventh Generation's, will get your dishes just as clean.

Photo credit: mastermaq / CC BY-SA 2.0