17

I am currently trying to buy a dish washer and just got a washing machine lately and I am really confused whether it is better to buy a machine which uses less water or one which uses less energy.

Example:

Dish Washer A:
Energy: 211 kWh/a
Water: 2520 l/a

Dish Washer B:
Energy: 220 kWh/a
Water: 1680 l/a

The cost for 1 kWh is 22,25 cents, the cost for 1000 l Water 1,85 eur, meaning the difference in annual costs is 2.0025 - 1.554 (delta_energy - delta_water) which is about 45 cents per year.

So it really comes down to: Do I want to save energy or do I want to save water?

(I do not live in an area with water or energy scarcity)

  • 7
    I suspect this depends on where you live. The answer should vary a lot between Las Vegas, USA and Bergen, Norway. – gerrit Apr 30 '13 at 23:49
  • Don't forget to account for the energy used to heat the water - Dishwashers (at least, in the USA) are connected to the hot water supply. – Johnny May 1 '13 at 21:39
18

Water takes energy to pump, filter and treat (and the treatment chemicals require energy to make), so it's likely a substantial part of the water cost goes to energy anyway.

Given that in your case you can save a massive proportion of water for very little extra electricity, I'd go with the water saving.

Secondly, it's often possible to run a lower temperature cycle, which will lower your energy use. The manual should have details. If you have the option on the model you purchase (and a suitable dwelling and climate, and some willingness), you may be able to skip the dry cycle and air-dry the dishes to save a substantial amount of energy.

If you have plastic items that go in the dishwasher, lower operating temperatures will increase the life of the plastic and may decrease any leaching of chemicals (eg Phthalates, BPA, which some believe contribute to cancer, endocrine disruption, etc).

If you ever want to collect your own water, it's a much more low-tech and thus more sustainable task than generating your own electricity, though @gerrit is correct that location does make a difference.

3

What if you take the situation to the extremes: Last drops of clean water on the planet - vs. the only left plant producing electricity. I would go for clean water in this case (I can find other sources of energy). If I won't have water, I will most probably die. If I won't have electricity I will not use my computer. See?

Would go for water in any case, actually. ("saving a massive proportion of water" vs "very little extra electricity"). When in doubt (like, counting small percentage variations of some method vs another), I prefer using common sense!

2

It depends on criteria and availability of energy and water around your area. If there is a scarcity of water there then you should not waste water and save it, so it depends on where you live.

Here there are many kinds of machines. Let me give one example; in an area around a river where lots of water is available there you can select a machine which saves more energy rather than water because energy is more precious than water, compared to other cases, an area of forest for example, where water is more precious.

  • 1
    What you've written is correct, and this would make a useful comment as it stands. It could be made into a very good answer, if you added specifics, examples or references about the conditions under which the best solution might switch between saving water and saving energy. – EnergyNumbers May 2 '13 at 18:15
  • @EnergyNumbers thanks man i edited my level best – Yadav Chetan May 3 '13 at 3:31
2

I don't believe anyone has mentioned the fact that most traditional electrical plants consume water. Additionally, this water is often evaporated and thus removed from the local water supply while--very unpalatability to think about--the water flowing through your plumbing may be taken from local surface water (i.e. a river or lake) and put back into local surface water (i.e. the same or different river or lake) as sewage.

http://spectrum.ieee.org/energy/environment/how-much-water-does-it-take-to-make-electricity

1

I am sure that washing machine is a waste of everything. You hardly ever need hot water and toxic washing substances to contaminate the sewage. But stupid machine does not understand that.

At first, you should live in a block of flats. This means that you consume 100 times less energy than individual cottage villager. Here we speak about 1 vs 100 energy (and other) savings is much more substantial than 211 vs 220, ok? But, you cannot afford for so much savings, right? This accounts for thermal electricity, which means that the power plants that produce electricity also heat your buildings and supply the hot water for free - you do not need neither additional heater nor heating in the washing machine.

Secondly, the machines are stupid. As human, you can see that most of the meals are not fat (yougurt is not fatty, just put your dish under the jet of cool water, help it with your had and see that the dish has cleaned up completely). Only pan after heavy fried pork needs some dishwashing liquids. Everything else (including yogurt) can be washed by the cool water, without dishwashing liquids. Such clean sewage is worth supplied on the fields, for crops growing as opposed to dishwashing liquid contaminated toxins and wastes 0 calories. The washing machines are expensive to produce, waste space and stupid - they do not see that 95% (and 100% for those who do not eat pork) of dishes do not need neither water contamination, nor energy. You just live your dishes in the water to soak for a while. The soaked dishes are easy to rinse with water to clean up. This is the same time you place the dishes into the washing machine and extract them afterwards. But machine is worse - it is stupid and treats all you dishes as absolutely fat. It wastes tons of electricity, dishwashing liquids and contaminates the waters.

Asking which dishwaser to use for sustainability is a mockery over the sustainability.

PS You need clean water only to wash the dirt away at the last stage of washing. The water is not clean anymore after you do that. However, you can reuse it to soak new dishes you want to wash later. (Remember, you need to soak in order the dirt to wash away effortlessly). I often do it. Additionally, I save my time. It takes time to wash and fill some container with water to soak. But, if I combine two processes, I save the environment and time simultaneously. Hardly, washing machine can reuse the gray water.

  • 1
    The part about 'you should live in a block of flats' is completely irrelevant here. There are always more extreme ways to reduce your footprint (e.g. become a homeless person and sleep under a bridge), but that is not the point here. – THelper Jan 7 '14 at 14:33
  • @THelper The point is that you can reduce the consumption orders of magnitude and fit into the ecological footprint without any sacrifice in comfort and sleep in your bed at optimal temperatures. The people, who struggle for every miserable improvement must know about it. – Val Jan 7 '14 at 16:20
  • @THelper In the second part, I have argued against using dishwashers. This means "to live under the bridge", in your terms - nothing different from what I argued in the first part. So, differentiating between the first and second part of my answer makes no sense! – Val Jan 7 '14 at 17:06
  • Arguing against using dishwashers in a question about using dishwashers is fine, though by community rules, possibly slightly off topic in this instance - I think it's still a helpful contribution. Telling people to change where they live is offtopic, and I'd argue not constructive. That kind of suggestion has its place, but telling everyone to jump to the extreme immediately tends to put people off of sustainability. Each solution needs to come in its own time and when a person is ready. – Nick Apr 18 '14 at 18:06
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    @Val, please don't get snarky. I'm not trying to prevent you from having a positive impact - I mostly agree with you on what real sustainability requires. When I refer to offtopic, I'm referring to the Q/A format of this site. If someone doesn't ask for help to the extent you're trying to provide it, then your suggestions won't be heard, and I think worse, will come off as nonconstructive. There are venues for those additional suggestions, but I don't think a question as specific as this one is one of them. – Nick Apr 20 '14 at 15:46

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