Where would I find reliable info on whether hand-washing dishes or using a dishwasher uses more water?
This study (Big PDF) from the University of Bonn is reliable and cited by both dishwasher manufacturers and conservation types as evidence that a modern, energy efficient dishwasher uses less energy and water than hand-washing on average.
But that result is based on the most efficient use of the machine versus the often inefficient methods of hand-washing that different people in the study used.
A very efficient hand-washing technique might be able to beat the most efficient machine in terms of energy and water use, but the average household among those studied used anywhere from 4 to 10 times more energy and water hand-washing due to inefficient practices.
For example in one part of the study 112 participants from 10 countries used an average of 103 liters of water to hand wash 12 place settings. This is far less efficient than a machine that cleaned the same number of dishes with an average of 12 liters. However, the individual results that produced that hand-washing average varied from under 20 liters to over 400 liters.
Thanks. My next-door neighbor says she won’t use her dishwasher because of the water bill. I only run it a few times a week (basically, when it’s full). I think laundry is probably a bigger water-usage culprit, and I’m not sure I can cut that down much while maintaining reasonable cleanliness (about 6-8 smallish washer loads a week).
I think you might be able to beat the dishwasher if you use a double bowl sink, fill one with soapy water and the other with clean water and not run water once you start. I don’t wash dishes that way and I don’t know anyone who does. And even so, in my house we run the dishwasher around every three days and I don’t think I can beat that.
For many years, I had one of those rolling portable full sized dishwashers that you have to roll up to the sink and hook a hose to the faucet. The washwater drains back up through a parallel hose and into the sink, where it goes down the drain.
Except when your drain stopper accidentally lodges closed before the drain cycle begins.
And that’s how I know that my dishwasher, which wasn’t particularly recent nor particularly high efficiency, still used less water than we used washing dishes by hand. It would fill to the brim, but not overflow, our sink when the stopper was closed. Since we filled the sink AND ran more water for rinsing when washing by hand, I knew we used more water for hand washing.
Just one tale, but maybe one that your neighbor will be able to grok as more concrete and immediate than scientists in a lab.
This is the nub of the question. If you wash the dishes etc under a continuously-running stream of water, a dishwasher wins very comfortably. If you use a bowl method, it’s probably a fairly close tie (although even then, only against a modern, efficient dishwasher)
The dishwasher probably is a clear winner there, but doesn’t that mean you have to own three sets of everything? (and have space to store it all)
When I put dishes into our dishwasher, I clean them pretty well before loading. How much you pre-clean should be considered.
Do you only own as many plates as people who live in your house?
I use the two-sink, no running water technique when I hand wash my dishes. Pretty sure this is quite efficient.
Also I don’t own a dishwasher. Never really understood the point of them.
“Three sets of everything” is probably a huge quantity for a large household that mostly eats sit-down meals. But between my wife and I, each day we probably use ~2 dinner dishes, 2-4 small plates or bowls for breakfast and snacks, 2 coffee cups, and 2 glasses each day. Add in a few pots and pans, and the dishwasher is filled over the course of three days. With ~12 of everything, there are plenty of clean plates even if we neglect cleaning for most of the week.
On the occasions I hand-wash dishes, I do the soapy-water sink for the wash, but don’t like the results of using a full rinse sink. Needs to be running water to get a rinse I consider acceptable.
As far as quantity of dishes, for a two-adult household plus the cat’s canned food twice a day, my ca. 12 place settings (we are missing an item or two) seems to be quite adequate for usually two or three days. It’s when I do a big cooking spree and wind up with pans and mixing bowls that it fills up faster :).
Well, I’ll pass it along, but her water bill is her concern. I’m busy enough with my own. 
We had a dishwasher like that when I was a kid (70s and 80s).
to use less water in the double sink, when hand washing, use plastic dish pans inside the sink. filling the naked empty sinks looses lots of heat to the sink, in order to have the water hot you need to refill or run water with the drain open to heat the sink. less space but better washing results. you don’t need to fill the suds side much either. dirty dishes to the right on the counter, dish rack in the left (with a drain pan underneath draining into the left sink), suds pan in the right sink, rinse pan in the left sink. right hand transfers from the right, left hand transfers to the left (this all for a normal right handed person as god intended).
the wash side should be hot and able to get your hands into. the rinse side can be hotter and allow you to dip the item before racking.
when using dishwasher you should run the hot in the sink until hot for most effective washing there. so you are running the water hot in either case so it’s a wash.
Now you do! Of course, I live alone and eat mostly fresh foods, no cookware. Somehow I haven’t ever gotten sick from using dirty dishes, so it must be effective.
Don’t they have high-tech “sinks” in Europe that vibrate the food off the dishes through ultrasound, no water at all?
No, but I don’t have three times as many, and certainly not three sets of everything other than plates that we’d use in a typical day (or room to store that many multiples)
I wear rubber gloves and I can use hot water straight from the tap (no cold added) - the extra heat really helps cleaning, and the gloves keep my hands from getting chapped from soaking.
In my case, by the time I start running low on any particular item, the dishwasher has generally accumulated enough contents to be worth running it.
No, this is wasteful.
According to tests by Consumer Reports, efficient modern dishwashers clean dishes equally well whether they are pre-cleaned & rinsed, or just put straight into the dishwasher. So in pre-cleaning them, you are wasting the water you use, and the energy used in heating it. Not to mention your time & effort. Don’t bother with that any more.
My high school boyfriend had a 1980s model dishwasher that wasn’t plumbed in so he used to sit the drainage hose in the kitchen sink. Once he left the plug in the sink by accident and ran the cycle; the sink didn’t overflow. I think the dishwasher is probably more efficient than me; I have to keep topping up the hot water as I wash.
It doesn’t matter how many people you have in your household. You just need as many dishes as will fill the dishwasher. Well, a few more, since you won’t always use the exact same dishes, and you might want to use some while the dishwasher is running. With fewer people it takes longer to fill it, and with more, it fills more quickly, but either way it’s the same number of dishes.
When I do the dishes by hand, I rinse with running water, but I start with little water in dishwater sink, and rinse into that sink until it fills up. Often all the rinse water goes into that side (although I’m not doing a full dishwasher worth of dishes when that happens).
I also use the cold “hot water” to pre-rinse the dishes, so I’m not just running water down the drain to warm it up.
ETA: Also, in cold weather, I leave the water in the sink to cool, so I reclaim some of the heat in the water.