For a long time, I’ve idly wondered how dishwashers compare to hand washing. I don’t like washing dishes (the counters in our kitchen are low enough that my back starts to hurt after a while), but there are always some dishes that either just don’t fit or seem too dirty to clean automatically.
First, I should explain how I wash dishes. Like most people, I fill our sink halfway with warm water and toss some soap in. Anything that’s really dirty sits in the water as I fill the sink for some extra soaking. I plug the other half of the sink as well to capture rinse water, which I keep cold. I still usually have to use the tap to get more rinse water for pots and pans, but small items like utensils or plastic containers I can just dunk, which is faster anyway.
My extremely scientific method of measurement was to use a measuring cup to put the rinse water into the rest of the water, then dump all of the water down the drain using the same measuring cup. Finally, I subtracted the amount of rinse water from the amount of total water. Okay, it’s not super accurate, but it’s accurate enough to give a reasonable estimate. In this particular situation, I was cleaning four or five very dirty pots/pans as well as some miscellaneous smaller items. Together, they probably would have made up a dishwasher load, but only because pots take up so much space.
For the entire process, I used 26 cups (1 1/4 gallons) of warm water for cleaning and 14 cups (3/4 gallon) of cold water for rinsing. For comparison, I use about a cup of water to wash my hands (turning off the tap while soaping, naturally). I can’t figure out a good way to figure out how much electricity was used to heat the warm water, since it’s not all hot and the water heater runs all the time. It seems pretty negligible, though.
Washing dishes in the dishwasher also uses a small amount of electricity, about 0.56 kWh (or over a day of running a CFL) as long as you air dry. Using the heat dry setting increases that a lot. Since we air dry, I’d call the electricity difference a wash.
A modern dishwasher uses about 6 gallons per load, while older machines can use as much as 8-10 gallons. Our dishwasher uses three times as much water as I did. That also doesn’t take into account pre-washing. We rinse anything with food on it before putting it in the dishwasher, which would make the dishwasher even worse. A larger family could fill and run a dishwasher in a day or two, which would make pre-washing less necessary. Since we only run the dishwasher once or maybe twice a week, the scraps begin to smell if we don’t pre-wash.
On the other hand, this analysis also doesn’t take into account that I wasn’t washing the items that I normally put in a dishwasher. It would probably take me at least twice as much water to clean all of the plates, silverware, and cups that fit into one load. Washing all of that myself would also take much longer and require a lot more kitchen space for drying.
I always thought that dishwashers had gotten pretty efficient and would give hand-washing a run for its money, but that doesn’t appear to be the case. Although dishwashing is probably about as good as hand washing for lots of dishes, it’s worse for larger items or if you use heat drying.
I’ll keep using the dishwasher for most things because it’s much more convenient and, as Maggie will attest, I hate washing dishes. However, I’ll make sure that the dishwasher is always full and I’ll continue to wash our larger, dirtier items by hand.