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Can you explain how dish washers are more efficient than hand washing? Is it about water use? What if you don’t run the water while you soap your dishes and onl

Can you explain how dish washers are more efficient than hand washing? Is it about water use? What if you don’t run the water while you soap your dishes and only rinse them in a rinse tub?

spijdar 5y ago
I haven't watched this video in a while so apologies if it's not specifically elaborated on, but I believe it's covered here: https://youtu.be/_rBO8neWw04 https://youtu.be/_rBO8neWw04 From memory yes, it's partially about water usage, but dishwashers are in general just pretty good overall about efficiently using energy to maximize "food grime removed" per unit of resources fed in. Even if you're careful with water usage while hand washing, I think a decent dishwasher will beat you. Another advantage is the dishwasher heats its own water, whereas with hand washing either you need to use a house-wide water heater or preheat water in a kettle or something, which will have its own energy wastes. This of course depends also on how your house's water is heated. One page I found googling elaborates on these ideas, concluding that you could potentially be more efficient hand washing, but only with a lot of effort: https://www.treehugger.com/built-in-dishwashers-vs-hand-washing-which-is-greener-4858791 https://www.treehugger.com/built-in-dishwashers-vs-hand-wash...
- Ichthypresbyter 5y ago
  >Even if you're careful with water usage while hand washing, I think a decent dishwasher will beat you. I once ran the dishwasher with the outlet hose in a bucket because the drain pump was on its way out. I expected to have to empty it several times, but at the end of the cycle there was less water in it than I would use to fill a washing-up bowl to do the dishes by hand (and the amount of dishes it cleaned might have required more than one bowl).
- nielsbot 5y ago
  Thanks. I read the treehugger link—pretty convincing overall. Not sure why my question was downvoted tho. (Not accusing you)
  - hutzlibu 5y ago
    In my observation unfair downvotes come, when people are angry at something and looking at anything that looks like a scapegoat to direct that anger, which can be anyone not expressing the same mindset they have. Which was you by asking that question that apparently was enough to mentally puts you in the "stupid treehugger camp". I would not worry about it too much and try to not take it personal. Their rational explanation is probably "how you can be so stupid for not knowing that common knowledge". And well, even though I am indeed a treehugger, I also knew about the efficency of dishwashers before and also assumed it to be common knowledge, but I would never downvote someone because of a genuine question adding to the conversation.
  - spijdar 5y ago
    I didn't downvote -- it's fair to be skeptical that a machine that spends hours making loud whirring noises would be more efficient than just scrubbing some dishes in the sink. And I don't want to careful about making unequivocal statements like "dishwashers are always more efficient", I've just heard some convincing reasons why dishwashers in particular are pretty cool and (unintuitively) efficient.
- hoseja 5y ago
  And it's disgusting and water where I live is cheap and plentiful. Hate water austerity imposed on everyone because of megacities and people living where people shouldn't live.
  - lovemenot 5y ago
    Large human population is an issue. But if you accept that as a premise, Megacities are more efficient in terms of resource usage than equally-sized but geographically dispersed populations. As for water usage, think first of agriculture, then industry. Only after that do cities come into play. Cities are relatively small water consumers.
    - bluGill 5y ago
      See my other post: agriculture water is not heated or treated. Thus cities use as much energy for their water despite only using a fraction. In all of the above water itself is not the issue as it isn't lost, just moved downstream until the water cycle (rain - which has always been non-uniform) brings it back.
    - throwaway0a5e 5y ago
      A city may be more efficient than lower population density on a per-capita basis but that is only tangential to the problem. A city in the California desert is not a good reason someone in NYC should have to endure a washing machine and dishwasher that are so stingy about water usage they are frequently ineffective at their primary task. >As for water usage, think first of agriculture, then industry. Only after that do cities come into play. Cities are relatively small water consumers. Where do those agricultural products get sold and eaten? <insert screeching about "taxing muh negative externalities" here>
    - ashtonkem 5y ago
      Typically even within residential areas the issues isn't people per se, it's lawns and golf courses. And those are absolutely not evenly distributed or used.
  - bluGill 5y ago
- hippari 5y ago
  You have to heat water to wash your dishes ? What kind of gravy sauce are you cooking in your pot.
JohnWhigham 5y ago
If you're careful about water usage and use cold water, you'll always beat a dishwasher. Another thing people often forget about dishwashers: you're supposed to pre-scrub the hard shit off the dishes. Well, you just did half the mechanical work yourself, why not finish it? I think part of it can also be (at least for me) upbringing. We always handwashed our dishes, and only used the dishwasher a couple times per year for big events.
- dijit 5y ago
  I grew up handwashing too but I disagree with your assertion. Firstly, you can't wash with cold water because soap doesn't activate with cold water, hot water also kills bacteria and helps cut through grease. Fats themselves are hydrophobic and without activated soap you wont get them off... enjoy your "filmy" dishes. Second, humans expend a lot more energy than you think. The act of standing and using our arms releases varying amounts depending on physical fitness but averages somewhere in the 1kg/h ballpark. https://www.jstage.jst.go.jp/article/jjphysiol/50/2/50_2_199/_pdf https://www.jstage.jst.go.jp/article/jjphysiol/50/2/50_2_199... Dishwashers use about 1800 Watts and are commonly run for 30 minutes, the average co2 in the USA is 0.92lbs per kWh. Meaning it's _basically_ the same. Then there's the freshwater usage, which is the real kicker, because dishwashers use significantly less freshwater, and freshwater filtering is the largest environmental impact of washing dishes (not the direct co2 output).
  - jamincan 5y ago
    Humans are expending energy regardless of whether they're washing dishes or not. The question is how much extra energy they expend when washing dishes over whatever they might do otherwise.
  - hippari 5y ago
    Human body will have to expense energy regardless whether you do it with house chores, or going to the gym, or a walk in the park.
  - ClumsyPilot 5y ago
    That energy use is likely an overestimate - thats mostky the heating element and it doesnt run the entire washing cycle or the water would boil
throw0101a 5y ago
> Is it about water use? What if you don’t run the water while you soap your dishes and only rinse them in a rinse tub? Yes: if your dishwasher has the Energy Star rating then it must use ≤15L of water using the normal cycle per the EPA. This is half the volume of a small sink and a one-third or less of larger ones. Most people run the water. In the US the average flow rate of a kitchen faucet is 8 L/min (2.2 gpm), so you can quickly use up 15L even just rinsing.
- bluGill 5y ago
  Most people use as much water rinsing their dishes to almost clean before putting them in the dishwasher.
- throwaway0a5e 5y ago
  Very few people are running the faucet anywhere near full blast when dish-washing. My faucet is very slow, about ~1gpm (I timed it once upon a time because I wanted to be able to put a number to how slow it is). When hand washing I run at maybe 1/4 or less of that. Everyone else in my household runs it at less.
AngryData 5y ago
Dish washers do reuse the same water far more than most humans would because it looks like you are washing dishes with filth. Most usually only run 3 small batches of water through them I believe. Not sure if it actually makes them more resource efficient versus mindful hand washing, but I wouldn't consider them inefficient at all.

Can you explain how dish washers are more efficient than hand washing? Is it about water use? What if you don’t run the water while you soap your dishes and only rinse them in a rinse tub?

spijdar 5y ago

I haven't watched this video in a while so apologies if it's not specifically elaborated on, but I believe it's covered here: https://youtu.be/_rBO8neWw04 https://youtu.be/_rBO8neWw04 From memory yes, it's partially about water usage, but dishwashers are in general just pretty good overall about efficiently using energy to maximize "food grime removed" per unit of resources fed in. Even if you're careful with water usage while hand washing, I think a decent dishwasher will beat you. Another advantage is the dishwasher heats its own water, whereas with hand washing either you need to use a house-wide water heater or preheat water in a kettle or something, which will have its own energy wastes. This of course depends also on how your house's water is heated. One page I found googling elaborates on these ideas, concluding that you could potentially be more efficient hand washing, but only with a lot of effort: https://www.treehugger.com/built-in-dishwashers-vs-hand-washing-which-is-greener-4858791 https://www.treehugger.com/built-in-dishwashers-vs-hand-wash...

Ichthypresbyter 5y ago
>Even if you're careful with water usage while hand washing, I think a decent dishwasher will beat you. I once ran the dishwasher with the outlet hose in a bucket because the drain pump was on its way out. I expected to have to empty it several times, but at the end of the cycle there was less water in it than I would use to fill a washing-up bowl to do the dishes by hand (and the amount of dishes it cleaned might have required more than one bowl).
nielsbot 5y ago
Thanks. I read the treehugger link—pretty convincing overall. Not sure why my question was downvoted tho. (Not accusing you)
- hutzlibu 5y ago
  In my observation unfair downvotes come, when people are angry at something and looking at anything that looks like a scapegoat to direct that anger, which can be anyone not expressing the same mindset they have. Which was you by asking that question that apparently was enough to mentally puts you in the "stupid treehugger camp". I would not worry about it too much and try to not take it personal. Their rational explanation is probably "how you can be so stupid for not knowing that common knowledge". And well, even though I am indeed a treehugger, I also knew about the efficency of dishwashers before and also assumed it to be common knowledge, but I would never downvote someone because of a genuine question adding to the conversation.
- spijdar 5y ago
  I didn't downvote -- it's fair to be skeptical that a machine that spends hours making loud whirring noises would be more efficient than just scrubbing some dishes in the sink. And I don't want to careful about making unequivocal statements like "dishwashers are always more efficient", I've just heard some convincing reasons why dishwashers in particular are pretty cool and (unintuitively) efficient.
hoseja 5y ago
And it's disgusting and water where I live is cheap and plentiful. Hate water austerity imposed on everyone because of megacities and people living where people shouldn't live.
- lovemenot 5y ago
  Large human population is an issue. But if you accept that as a premise, Megacities are more efficient in terms of resource usage than equally-sized but geographically dispersed populations. As for water usage, think first of agriculture, then industry. Only after that do cities come into play. Cities are relatively small water consumers.
  - bluGill 5y ago
    See my other post: agriculture water is not heated or treated. Thus cities use as much energy for their water despite only using a fraction. In all of the above water itself is not the issue as it isn't lost, just moved downstream until the water cycle (rain - which has always been non-uniform) brings it back.
  - throwaway0a5e 5y ago
    A city may be more efficient than lower population density on a per-capita basis but that is only tangential to the problem. A city in the California desert is not a good reason someone in NYC should have to endure a washing machine and dishwasher that are so stingy about water usage they are frequently ineffective at their primary task. >As for water usage, think first of agriculture, then industry. Only after that do cities come into play. Cities are relatively small water consumers. Where do those agricultural products get sold and eaten? <insert screeching about "taxing muh negative externalities" here>
  - ashtonkem 5y ago
    Typically even within residential areas the issues isn't people per se, it's lawns and golf courses. And those are absolutely not evenly distributed or used.
- bluGill 5y ago
hippari 5y ago
You have to heat water to wash your dishes ? What kind of gravy sauce are you cooking in your pot.

JohnWhigham 5y ago

If you're careful about water usage and use cold water, you'll always beat a dishwasher. Another thing people often forget about dishwashers: you're supposed to pre-scrub the hard shit off the dishes. Well, you just did half the mechanical work yourself, why not finish it? I think part of it can also be (at least for me) upbringing. We always handwashed our dishes, and only used the dishwasher a couple times per year for big events.

dijit 5y ago
I grew up handwashing too but I disagree with your assertion. Firstly, you can't wash with cold water because soap doesn't activate with cold water, hot water also kills bacteria and helps cut through grease. Fats themselves are hydrophobic and without activated soap you wont get them off... enjoy your "filmy" dishes. Second, humans expend a lot more energy than you think. The act of standing and using our arms releases varying amounts depending on physical fitness but averages somewhere in the 1kg/h ballpark. https://www.jstage.jst.go.jp/article/jjphysiol/50/2/50_2_199/_pdf https://www.jstage.jst.go.jp/article/jjphysiol/50/2/50_2_199... Dishwashers use about 1800 Watts and are commonly run for 30 minutes, the average co2 in the USA is 0.92lbs per kWh. Meaning it's _basically_ the same. Then there's the freshwater usage, which is the real kicker, because dishwashers use significantly less freshwater, and freshwater filtering is the largest environmental impact of washing dishes (not the direct co2 output).
- jamincan 5y ago
  Humans are expending energy regardless of whether they're washing dishes or not. The question is how much extra energy they expend when washing dishes over whatever they might do otherwise.
- hippari 5y ago
  Human body will have to expense energy regardless whether you do it with house chores, or going to the gym, or a walk in the park.
- ClumsyPilot 5y ago
  That energy use is likely an overestimate - thats mostky the heating element and it doesnt run the entire washing cycle or the water would boil

throw0101a 5y ago

> Is it about water use? What if you don’t run the water while you soap your dishes and only rinse them in a rinse tub? Yes: if your dishwasher has the Energy Star rating then it must use ≤15L of water using the normal cycle per the EPA. This is half the volume of a small sink and a one-third or less of larger ones. Most people run the water. In the US the average flow rate of a kitchen faucet is 8 L/min (2.2 gpm), so you can quickly use up 15L even just rinsing.

bluGill 5y ago
Most people use as much water rinsing their dishes to almost clean before putting them in the dishwasher.
throwaway0a5e 5y ago
Very few people are running the faucet anywhere near full blast when dish-washing. My faucet is very slow, about ~1gpm (I timed it once upon a time because I wanted to be able to put a number to how slow it is). When hand washing I run at maybe 1/4 or less of that. Everyone else in my household runs it at less.

AngryData 5y ago

Dish washers do reuse the same water far more than most humans would because it looks like you are washing dishes with filth. Most usually only run 3 small batches of water through them I believe. Not sure if it actually makes them more resource efficient versus mindful hand washing, but I wouldn't consider them inefficient at all.