Disherwasher vs. hand washing

April 10, 2009 10:18 AM

Dishwasher vs. hand washing. Assuming we run the dishwasher only when it's full, which method uses less water and fuel?
posted by markcmyers to science & nature (11 comments total)

What's your hand-washing method?
posted by otherwordlyglow at 10:25 AM on April 10

It's hard to say.

Summary: the result seems to be that if both methods are done with maximal efficiency it's about a wash.

No, seriously, they two can be approximately the same in terms of water and fuel consumption. You have to factor in the costs of producing and installing the machine, but considering that they usually last about a decade, this adds very little energy use to each washing. The catch is that it's a lot easier to be inefficient if you're doing things by hand, and hand-washing takes a lot longer.
posted by valkyryn at 10:29 AM on April 10 [1 favorite has favorites]

It depends on how you wash the dishes by hand.
posted by torquemaniac at 10:29 AM on April 10

The U.S. Department of Energy says:

It's commonly assumed that washing dishes by hand saves hot water. However, washing dishes by hand several time a day can be more expensive than operating an energy-efficient dishwasher. You can consume less energy with an energy-efficient dishwasher when properly used and when only operating it with full loads.

posted by grouse at 10:30 AM on April 10

Slate's Green Lantern covered hand vs. machine washing awhile back. The gist is that when used most efficiently it is very hard to beat the machine (and the hand wash technique needed to come close is unlikely the one you deploy).
posted by mmascolino at 10:31 AM on April 10 [1 favorite has favorites]

Check out this Green Lantern article about this very issue.
posted by bluejayway at 10:32 AM on April 10

Valkyryn beat me to the link. Sorry for the repeat.
posted by bluejayway at 11:04 AM on April 10

Don't forget that your time is also worth something. You could be doing something that you want to do.
posted by Confess, Fletch at 11:13 AM on April 10

These studies are invariably funded by the dishwasher & detergent manufacturers, from a quick google VHK seem to fund a few - heres their client list (Bosch Electrolux, Unilever) I wonder if that gives them a slight bias?

Stamminger didn't examine the considerable amount of energy and materials required to make and transport the dishwasher. He also didn't consider the environmental impact of the detergents. For example, many dishwasher tablets use phosphates to help with anti-scaling which then contribute to the process of eutrophication, whereby over-production of algae in water leads to lack of oxygen for aquatic life.

The Bonn study assumes the dishwasher is always used with a full load, but theres no research done as to the typical use of a dishwasher (i.e. people may say they always do full loads but after a few weeks do they get lazy and start running a whole cycle for 2 plates?)

Similarly does the average family really leave their dirty dishes to air dry for two hours before hand washing? Thats enough time to watch an entire movie and then take the dog for a walk.

Everyone wants their favourite labour saving device to be green, but wanting isn't enough to make these studies ring true.
posted by Lanark at 2:26 PM on April 10 [1 favorite has favorites]

Lanark, in my experience "laziness" prompts people to run the dishwasher only after they have tried, and failed, to cram more dishes into it.
posted by Mars Saxman at 2:52 PM on April 10 [2 favorites has favorites]

^ just as long as the dishwasher isn't mostly filled with clean dishes.
It may seem crazy to open a dishwasher find it full of clean plates, add one dirty plate and run the whole cycle again, but I have seen people do exactly that!

I think the driver behind that kind of behaviour (in the UK at least), is the trend for very small kitchens designed with no storage space, a dishwasher and a tiny hand sink - too small to even get one plate in.
posted by Lanark at 3:13 AM on April 11