How much, if any, water do dishwashers save?
Many people claim that dishwashers save water over washing by hand. I found this hard to believe, so I did some research and some measuring.
What I found for sure, is that is depends on how you hand wash your dishes. If you do it by running the water (ie. not filling a sink) you will use much more water than a dishwasher (I’ve seen estimates of 75L). No surprise here… So don’t do that! Fill up a sink instead!
Based on my practise, with a double sink, where my wash is between 4.5 cm and 6 cm deep, and I rinse by turning on running water in batches once the second sink is full of dishes to rinse, below is my usage:
- Wash: 41.5 cm x 35.5 cm x 4.5 cm deep = 6.6L
- Rinse: estimate same height (probably less) = 6.6L
I found that Energy Star dishwashers use 4 gallons per load, or 15L. My total for hand washing is about 13L. So, that’s pretty comparable.
But, if you pre-wash or rinse your dishes before using the dishwasher, than hand washing wins. If you have an older dishwasher, then it won’t be as efficient. And if you use high temperature water or heat to dry dishes in the dishwasher, any advantage is also lost.
So, to me, the two ways are pretty even. If you prefer to have a dishwasher, get one that saves water and use it wisely. Make sure you buy dishwasher detergent without phosphate (see ranking of effectiveness of detergents and the nasty about phosphate). If you wash by hand, use as little water as possible and find a phosphate free detergent as well.
Comments(6)
hi crys,
thanks for the first-hand research. one possible missing link might be that a dishwasher can usually wash more dishes than one sink load…especially if they’re greasy. normally when I do a full counter top of dishes I have to use a couple sinkloads of water, where the dishwasher might only be one load. basically, there are SO many considerations in this debate, it would be hard to make one blank statement one way or the other, as you mentioned. and of course pots need to be washed by hand (at least, I would).
thanks for the research! -e
I was estimating that the dishes I did this am with that level of water would be close to a load, but maybe not. I agree, a dishwasher is comparable by my hand washing method.
We have a dishwasher which empties into the sink so I can put the plug in and see how much water it uses. It will almost fill the sink which I guess is about 15L. More water than I would use to handwash, but less if you have another sink full to rinse. You may also need to refill the washing up water if it gets really dirty. I reckon dishwashers use less, not to mention the arguments it saves!
Good reaserch Crystal
We have tested both methods and found similar results to yours. We have added Grey water systems and water tanks to our house to offset water wasteage from washing dishes ect. Our grey water is supplied by the bath and shower water and is distrubuted though drip irrigation thruogh out our garden. The rainwater tanks supply water for washing clothes, flushing toilets and watering pot plants and the like.
Question: How about the energy used to heat the water in the dishwasher? Our dishwasher rinses the water, holds the dishes while heating the water and then washes and dries the dishes. And that heating is on top of the water heater we already own.
Carla: That’s definitely another factor in the total energy use. It’s not just the total amount of water. I think too there are more options for environmentally friendly normal dish soaps than for dishwasher soaps.