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I've been considering a dishwasher, but there are a range of different opinions on if they save water (or even energy) or not. Do we have any sources one way or the other?

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    it depends on your usage – Yadav Chetan May 1 '13 at 12:03
  • From my experience I would say no. Most people "pre-wash" their dishes before putting them in a dishwasher. I would find more sustainable ways to hand-wash if you want to figure ways to save water in the long run. – Xarcell May 2 '13 at 23:20
  • How do you do the dishes now? How are you heating your water? – THelper May 3 '13 at 7:55
  • Also, there are many dishwashers that kick ass at washing dishes without rinsing. – Enjabain Feb 7 '14 at 23:30
  • I can only repeat my answer in sustainability.stackexchange.com/a/2422/476. The washing machine is a waste of water and energy (I am not even concerning the resources needed to produce these machines). Regarding the water, the stupid machine not only wastes but also contaminates the water (so that sewage is toxic and cannot be used even for watering the plants). – Val Feb 8 '14 at 0:10
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I disagree that dishwashers, compared to hand washing, will not save energy.

First of all, as with almost anything, it depends how it's done. If you run your dishwasher half full, that's going to be bad for energy and water use. Similarly, if you hand wash, with the hot water running the whole time, that's bad. So, either technique requires tuning the way you use it.

However, dishwashers have some inherent advantages, in that they're closed units. Being closed units allows them to build up heat and humidity. That helps the washing process. It also means that water sprayed on dishes in the upper rack can then filter down, and rinse dishes in the lower rack. The same goes for water that's sprayed horizontally.

Also, understand that a dishwasher is fundamentally different than a clotheswasher. A dishwasher doesn't need to spend a lot of energy physically moving around heavy clothes and a large tankful of water. Much of the energy a dishwasher uses is in heating the water. But, that happens with handwashing, too. Hopefully, you can intuitively see that if the issue is largely about heating water, it's easier to do so in an enclosed space.

Rather than try to reproduce a thorough analysis myself, I'll point to an article on treehugger.com. An important excerpt:

These numbers indicate that it's possible to be more efficient when hand-washing, but it's pretty tough. Can you successfully wash and rinse a soiled dinner plate in just over a cup of water? If you can keep the water use low, equal to an efficient machine, you'll require less energy, but doing an entire load of dishes in 4 gallons of water is roughly equivalent to doing them all in the same amount of water you use in 96 seconds of showering (using a showerhead that emits 2.5 gallons per minute).

So, as long as you don't often run your dishwasher when it's only half full of dirty dishes, or unless you are very miserly with your water use (or have an old, inefficient dishwasher), the automatic dishwasher is likely to be more efficient. That is to say, it's possible to use less water and energy by hand washing your dishes, but it's not easy.

I'll also address another point in the other answer.

When you automate things, you substitute electricity for manual energy.

"Manual energy" doesn't come from nowhere. It comes from the food we eat. Powering a human being involves converting sun, water, and soil into food, processing the food, then letting the human convert it into usable energy. The human body, combined with the agricultural inputs, do not represent an efficient "machine".

I'd also offer the somewhat economic argument regarding opportunity cost. The time you'd spend handwashing dishes might better be spent on something else. If you're interested in sustainability (yeah!), then consider what other sustainable projects you could work on with the X hours a month you'd spend handwashing dishes. Perhaps add some insulation to your attic? Add mulch to your garden? Brew biodiesel yourself?

All these things matter in the overall assessment of what saves energy, or makes energy usage more sustainable.

Anyway, if I had to be tied down to a short, simple answer, I'd say that yes, a dishwasher does (tend to) save water.

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    While it's true that humans are not efficient at turning food energy into work, I think that in today's society, most people tend to take in too many calories, and some even pay money and use expensive machines and electricity to burn off those calories. So expending more human energy to wash dishes is probably a net positive for sustainability (and physical fitness). – Johnny Jan 29 '14 at 2:09
  • @Johnny, what you are advocating is "spending" more calories because we're taking in too many. That's the wrong way to approach sustainability. The sustainable answer is to eat the right amount. Physical fitness is a topic for another site, and beyond the scope of this question. – Nate May 4 '16 at 3:57
  • Great answer, but even though the question focuses on water usage, the extensive answer should probably at least mention that we should keep in mind that the dishwasher's construction, repairs, recycling and disposal do require materials, energy and water, and the machine occupies a significant amount of space in your home. Furthermore, the time you save not washing dishes might also end up being used (at least in part) cleaning, troubleshooting, repairing and disposing of the dishwasher. – stragu Aug 17 '17 at 6:32
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First of all, dishwashers, compared to hand washing, will not save energy. When you automate things, you substitute electricity for manual energy. At best you are substituting fuel for food (but more likely you'd use that food anyway).

For water, there are a fair number of factors. These include how you wash dishes, how greasy the dishes are, how much water your dishwasher uses, and much more. For places which have separate irrigation water lines, I would actually recommend finding out whether the irrigation water is of sufficient quality to use for washing dishes (the required water quality to safely wash dishes is lower than that to drink). I would suggest that if the water is safe to play in (keep in mind kids, particularly, tend to ingest small amounts of water as they play), it is probably safe to wash dishes in. Here dishwashers have an advantage if they heat the water up to disinfecting levels and may allow you to use less potable water.

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    Do you have a source for your statement about dishwashers not saving energy? Because, based on what I've found, I would disagree. – Nate May 2 '13 at 12:11
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    While this may be correct if you wash in cold water and are careful to minimize water use, modern high-efficiency dishwashers are much more water and energy efficient than hand-washing with hot water (the standard practice in the USA). The energy efficiency comes mainly from water efficiency when washing with hot water, but that is important because almost everyone uses hot water to wash dishes. – Evan Johnson May 2 '13 at 18:15
  • At least where I am, I never run hot water all the time. Of course having only small hot water heaters in the showers only helps..... – Chris Travers May 3 '13 at 3:10
  • You don't have to wash manually with hot water, only because most Amis do that. It's a difference. Using washing machine, you have no option. – Danubian Sailor Jun 1 '13 at 11:34
  • Is it usual in the US to wash in hot running water? I usually have a tub of hot water, just wide enough for a plate and perhaps 150mm deep. – Flyto Jan 29 '14 at 9:13
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I live in Mexico and use only water collected from the roof during the 3 month rainy season - we soap the dishes first, no runnning water, then rinse them all at the same time. For two people, mixed diet (some meat and fish) this rarely takes more than 2 gallons at a time, often less for a day's worth of dishes. Dishwashers are way to costly (purchase cost wise) to consider and hard to get - I'd have to drive 40k to look at one, and in any case, a cash expenditure like that is a heavy opportunity loss on it's own.

I'd say stay with handwashing and practice getting to minimum water use using pre-soap and scrub method followd by rinse unless you have already spent the money on an up-to-date dishwasher.

I come to the US quite often. Here I see folks pre-rinse under running water more often than no, just because that's their habit (maybe from having earlier dishwahers??). And I think - hey dude - you should try living with 40.000 liters for the year and see what happens then! You'd be out of water before 4 months is up! And, consider this too - half your potable water goes down the toilet too!

So, I guess it is a little contextual, no?

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First you have to rinse the dishes before you put them in the dishwasher. This is like washing them without soap. We are whole food/plant based, which means no grease or oil. It's quicker and more efficient for us to hand wash our dishes.

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

  • Welcome to Sustainable Living! In what respect is handwashing more efficient? Time, money, energy usage? How do you know this? Also, I don't think rinsing before putting dishes in the dishwasher is necessary. I usually remove food left overs with a spoon and then place the dishes in the washer. – THelper Jan 29 '14 at 7:55
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Dishwashers will not save any type of energy. We live off grid and only have rain water and there is no ground water available either.

Wash your dishes in a small sink, and only when you have enough dishes to clean to use the water you use in the sink.

The dishwasher also uses power to heat the water, which also uses more power than either gas or solar heated water.

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    Welcome to Sustainable Living! How exactly do you know that dishwashers will not save any type of energy? It will be true in your case, living off the grid, but what if you consider other situations? – THelper May 3 '13 at 7:53
  • The answer will depend on every load you put into the dish washer and brand/capacity. Only way to know for sure is to measure the water the dishwasher uses for a wash, and compare it to the amount of water you put in your sink. And yes, the main concern for us is the energy used to heat the water. But this is the same for anyone with a solar hot water system. In general, dishwashers use cold water then heat it using electricity, but if you have an instantaneous gas or solar heated water, then washing in the sink will cost less heating the water. – Jason Pascoe May 3 '13 at 11:16
  • But when you normally do the dishes by hand with water heated by electricity, a dish washer might be more efficient (depending on the amount of water you heat and use). – THelper May 3 '13 at 11:46
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    I agree, but if you still have an electric hot water heater, then you should change it to at least gas if you cant change it to solar. Best option is solar with instantaneous gas with digital temperature adjustment for boost. – Jason Pascoe May 3 '13 at 12:19
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    This is incorrect (see my answer for support). Additionally, many dishwashers now let you choose whether to accept hot water from the hot water supply (which could certainly be provided by a solar heater), or also add extra heat at the dishwasher itself. Similarly, whether or not to provide heat to dry the dishes is commonly an option. I use a dishwasher, but do not select Water Heat and do select No Heat Dry. Also, natural gas water heat is not better, if you have the option to buy renewable electricity. I have an electric water heater, and buy 100% renewable electricity. – Nate May 3 '13 at 22:10

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