Dishwasher versus handwashing for multiple small loads: efficiency pros and cons...

[hlthe2b]

Ok, during the week and for the indefinite future, I am working at home and sole member of the household--weekends are quite different.

But for weekdays, I tend to just hand wash all my dishes throughout the day--it is relatively quick and usually includes pieces I use daily that would make including in batched dishwasher loads a bit self defeating.

But, what do you think? While I try not to waste water, is this really LESS energy efficient than using the dishwasher? (I do have an energy-saving air dry feature on the dishwasher, but it is more than 10 years old and probably not all that efficient).

What do you think?

[intaglio]

1. As I understand it dishwashers are far less efficient than handwashing

They use far more water, and electricity. Oddly, for anything more than single items clothes washers use less water than hand washing and may be electrically more effective. Tumble dryers are energy vampires, air dry if at all possible; in the UK is is actually cheaper to use launderette dryers than home dryers.

[Manifestor_of_Light]

2. Tap water is not hot enough to kill the germs.

From the Arizona Dept. of Health Standards:

Hot-water sanitizing -- through immersion (small parts, knives, etc.), spray (dishwashers), or circulating systems -- is commonly used. The time required is determined by the temperature of the water. Typical regulatory requirements (Food Code 1995) for use of hot water in dishwashing and utensil sanitizing applications specify: immersion for at least 30 sec. at 77°C (170°F) for manual operations; a final rinse temperature of 74°C (165°F) in single tank, single temperature machines and 82°C (180°F) for other machines. Many state regulations require a utensil surface temperature of 71°C (160°F) as measured by an irreversibly registering temperature indicator in ware washing machines.

The recommended highest temperature for tap water to prevent burns is 120 degrees Fahrenheit.

That is far lower than the specs for sanitation of dishes. This is why I always use a dishwasher.

[hlthe2b]

4. Yes... especially during cold & flu season... or in a commercial kitchen a madatory...

But, like washing hands with regular soap, the point for routine dish-washing is to reduce bacteria to a low level, not to necessarily "sterile." And, since they are all going to get the dishwasher on the weekends, I'm not sure that argues for routine use. Dishsoap is also antimicrobial, and I frequently do a 100% white vinegar spray rinse just to remove soap scum. So I think I'm fine for routine purposes...(We all survived our mothers/grandmother's hand-washing of dishes, after all)...

[Manifestor_of_Light]

7. My mother and grandmother had dishwashers in the 1950s.

My mother insisted on having one, built-in under the counter, to kill the germs.

She considered them a necessity and I do too. I took microbiology and have a biology degree. You do not have to have a biology degree to know about germs, but it doesn't hurt.

The first one I remember was a Hotpoint brand. Then it was a Frigidaire.
Now I live in my grandmother's house, and am using a Kitchenaid that was installed in the 1990s probably.

I've gotten food poisoning from eating food at someone else's house who probably didn't wash her counters off.

[hlthe2b]

8. No one is saying they aren't a good idea.. Food handling practices are just as likely

to be the cause for the food poisoning... Leaving food out, failure to bring food to and hold at a high enough internal termperature, cross contamination and failure to cook thoroughly, etc., etc. Not to mention that one can sterilize dishes and utensils on a continuous basis, but all it takes is one pair of unwashed hands among household members (and some circulating Norovirus) to render that all meaningless. Studies have shown that the average American, even many health care professionals, does not wash hands regularly nor thoroughly, even after using the restroom.

I can assure you, after a decades long career in infectious disease research and prevention, I do appreciate your point, but one can hand wash dishes and do so in a safe manner, even adding a bleach water rinse during cold/flu season when necessary. Dishwashers afford far more protection, I grant you, but it is not absolutely necessary.

[Kaleva]

13. Dishwashers use tap water.

Residential dishwashers are supplied by the same hot water line that feeds the kitchen sink faucet.

I've installed many dishwashers and I've never had one where the instructions said to hook up the supply line directly to the output of the water heater and before the mixing valve (if one is installed).

To do what you say, one would have to have a dishwasher with a booster heater and those are very expensive and mostly used in commercial applications.

http://www.acemart.com/equipment/plumbing-supplies-dishwashers/dishwashers/undercounter-dishwasherbooster-heater-hoblxih-3/prod8221.html

[SeattleVet]

3. Our new dishwasher is extremely efficient

It uses ~2 gallons per load, and the estimate is about $15 electricity per year (off the low end of the EPA scale, which starts at $19). I can't wash a pot with 2 gallons, so pretty much everything goes in. Even small loads are a savings overall.

(This is a Fischer-Paykel drawer model.)

[Curmudgeoness]

5. I hand wash and

do not think that it uses as much energy or water as a dishwasher. But I don't really know. But really, is it a significant difference? I don't think it is. My opinion of the this-or-that being more efficient arguments is that it often is only a small savings one way or the other, and can be affected by things like how you do it. I wash a small amount of dishes in about an inch of hot water with dish soap, and I think that is not normal---so how do they factor things like that into their statistics? To me, it is just easier and part of that reason is what you said about things you use all the time.

As to whether the tap water is hot enough, I am at a loss as to whether that can be factored in----doesn't the dishwasher hook up to the same water supply as the faucet?

[Manifestor_of_Light]

6. Yes, but dishwashers have a heating coil in the bottom to get the water hotter.

You can also set it to heated dry, which means that steam comes out the front vent.

There is a big difference between tap water at maximum 120 degrees F., and the 170 degrees recommended for sterilizing dishes. Soap won't make up for that. Just because it burns your hands does not mean it will kill germs.

[Curmudgeoness]

9. OK, I did know about the heat drying, but

the OP said that his/her dishwasher has air dry. I assumed that meant it did not steam the dishes. I did not know about heating the water also.

But with that said, I suppose that I don't worry as much about germs as many people do. I don't obsess, I don't bleach and sterilize everything all the time. As a science major in college, I am aware of sterilization techniques, but I don't think that anything in my house has ever been sterilized. And still I am alive, healthy, and have been sick from work twice in the ten years I have worked there. I guess that people who are very worried about germs should not listen to my suggestions.

[Kaleva]

14. No. They are used to help keep the water hot and to dry

Their purpose is not to get the water hotter.

"The heat coil aids in keeping the wash water hot, as well as in drying the dishes. "

http://www.ehow.com/how_12092870_replace-heat-coil-ge-profile-dishwasher.html

Many dishwasher installation manuals suggest setting the temperature of the water heater to 140 degrees for optimum cleaning performance. However, they also warn that temperature can cause scalding.

[cbayer]

10. I am lucky to have a saltwater pump.

I wash and rinse dishes using saltwater, then final rinse with fresh.

I don't really think it's important to sterilize eating and cookware. If you use an antibacterial soap and get all the food off, why should you have a problem?

[Flaxbee]

11. Treehugger discusses the issue here:

http://www.treehugger.com/kitchen-design/built-in-dishwashers-vs-hand-washing-which-is-greener.html


I don't have a dishwasher; haven't since 2004 --- but it's only me and my husband 99.999% of the time so there isn't a big volume of dishes. I'd still like one, though. I have some rubber gloves I use and make sure the water is very hot when rinsing. The soap you use should kill any bacteria ... then a good rinse would be fine.

But then again, we don't prepare or eat much meat, so our germ load does tend to be lower than people who touch/prepare raw meats.

[hlthe2b]

12. Thanks, that article was what I was looking for...

Seems like if I just hand wash the items I use daily and put the rest in the dishwasher to run as a "batch", I might be best off. I'm so used to just doing them by hand, but I probably do use more water than I should, even though I am fairly careful Dishwashers are a "God-send" for big families, but when it is just one or two, it hardly seems worth it.

[RebelOne]

15. I do not even own a dishwasher

and hand wash all my dishes. I live in a mobile home and there is no room in the kitchen for a dishwasher. Fortunately, it is only me I cook for, so there are not many dishes. But I do save a lot on water and electricity.

[yardwork]

16. I usually live alone, and the only reason I use my dishwasher is to wash the cat food bowls

[jade3000]

17. Doesn't vigorous scrubbing matter?

In addition to temperate and soap, doesn't vigorous scrubbing have an impact on germs? Surely some of the little buggers must get killed when a scrub brush or rag or rubbing up & down the surface of a dish or utensil.