Which Is Greener? Dishwasher Or Hand Washing?

Which is greener?  Using a dishwasher or hand washing the dishes?

Seems like a simple question, doesn’t it?

But it’s not.

Here are some of the elements in this discussion:

• How much WATER is used?
• How much POWER is used?
• Are your plates actually CLEAN?
• And, finally, though it’s not a green issue: How much TIME does it take?

On top of these, there are a few other matters that are harder to nail down:

• How much DETERGENT is used (because manufacturing cleaning products also has an ecological impact)?
• Are you factoring in the energy cost of manufacturing the dishwasher in the first place (then spreading it over, say, a ten-year life cycle)?
• What are you comparing the dishwasher to — manually washing your dishes under constantly running electrically-heated hot water or a cold water wash in a shallow sink?  It seems that most writers are thinking of the way that a typical household does things.  Sounds like a useful assumption, right?

Why dishwashing machines win out over hand washing in almost every circumstance

And that, by the way, is the conclusion of most studies, including the American Council for an Energy-Efficient Economy, Consumer Reports, the Environmental Protection Agency’s Energy Star Program, the Natural Resources Defense Council, and a study at the University of Bonn in Germany.

Reason 1: They use LESS WATER.
“You use up to 27 gallons of water per load by hand versus as little as 3 gallons with an ENERGY STAR-rated dishwasher.” [source: nrdc.org]

Reason 2: They use LESS POWER.
“A new ENERGY STAR certified dishwasher uses less than half as much energy as washing dishes by hand and saves nearly 5,000 gallons of water a year!” [source: energystar.gov]

Reason 3: They CLEAN BETTER.
And that’s for two reasons. Firstly, temperature. Your hands cannot take the high temperatures that many dishwashers are set to. 140-145° F is really hot but it gets dishes really clean.  And secondly, modern dishwashers have soil sensors. Nifty detectors that know how dirty your load is, and if it’s not so bad, they wash less.

The Guardian reported that there is “nearly 400 times more bacteria left on the dishes after [hand] washing”.  Ouch!

Reason 4: The TIME you save.
“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.” [source: washingtonpost.com]

Dishwashing tips to help save the planet (and money too)

• No need to rinse your dirty plates before loading them into the dishwasher.
• Scrape food off first, however.
• Only run the dishwasher when it’s full.  No half loads.
• Choose an energy efficient model next time you buy.  The higher the Energy Star rating, the better.
• For an even greener option, “use the timer setting to run the dishwasher in the middle of the night.  This way, you’ll be using the grid at a time of low demand, which means the least efficient and dirtiest power stations won’t be running and, as a result, each unit of power will have a slightly lower carbon footprint.” [source: theguardian.com]

Want to know more? For an easy-to-read discussion of the numbers behind this, you could do worse than reading this piece from TreeHugger.

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