Smarter Living: Energy

Wash by hand or run the dishwasher? Spouses and roommates have long been divided over the question of which uses more water and electricity. And it's just complex enough to make for a good argument among those inclined to debate the issue. The short answer is that running a new Energy Star dishwasher loaded to capacity is the best, most efficient method of doing the dishes. It's also the least time-consuming. But efficient hand-washing is a close second in terms of electricity and water use, particularly if your only other option is to use an older machine. And whether or not you own a dishwasher, you can clean your plates more efficiently by scraping rather than rinsing. Read on for the full details.

As a baseline, remember that water flows out of your tap at a rate of 3 to 5 gallons per minute. New Energy Star-qualified dishwashers use as little as 3 gallons of water and 1 kilowatt-hour of energy per load. New machines not only use less water and energy but are also better at cleaning dishes, and manufacturers recommend against rinsing dishes by hand before loading a washer. This practice can waste up to 20 gallons of water, while the machine's rinse cycle requires only 1 to 2 gallons. But if you must rinse your dishes beforehand, use cold water instead of hot.

Water Electricity
1. New Energy Star machine

3-5 gallons

1 kWh

2. Efficient hand-washing

Up to 8 gallons

1 kWh

3. Older machine

Up to 15 gallons

2-3 kWh

4. Regular hand-washing

27 gallons

2.5 kWh

Washing by hand is almost as good as using a new machine, provided that the hand-washer uses efficient techniques. Installing an aerator in your faucet can save 3 to 4 gallons for every minute that your tap is running. Scraping food off, soaking dishes in a basin of soapy water before getting started, and not letting the water run while you wash every dish will help you save water and energy. And it's best to have two 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. In any event, 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.

Regular washing by hand takes last place; it can use a whopping 27 gallons of water and 2.5 kWh of electricity if you let the water run the whole time.

If you haven't replaced your dishwasher in more than a decade, think about switching to a new model. You'll get a return on your investment: If your dishwasher is at least 10 years old, you can save $25 to $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 Web site'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 the water temperature according to 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 "energysaving" 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 have to run it only 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.

Learn More

Salvage or Scrap: Dishwashers

last revised 11/9/2011

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