Hey Mr. Green
I’m trying to convince my husband that using the dishwasher is more efficient than washing each dish separately. I intuit that this is the case, but I haven't figured out how to articulate it to him. –Gabrielle in Oakland, California
Although it shatters the code of macho solidarity, Mr. Green is duty bound to report that you are right and he is wrong.
A typical manual dish-washing stint averages about twice the water and energy of a modern dishwasher. This has been verified by German research, which, as we all know, is impeccable. And, according to the EPA, a dishwasher will typically save 5,000 gallons of water, $40 in utility costs, and 230 hours of your time in a year.
Of course, we're talking about a full load in the machine. If you put only a few dishes in and run it through a cycle, hand-washing could win. Or, if the hand-washer is atypically efficient, he or she might outdo the machine. Also, we’re assuming that water isn’t wasted by unnecessary rinsing of dishes before placing them in a dishwasher. Scraping crud off with a spatula or lightly rinsing is all you need to do, provided you don’t delay and let stuff dry out and glue itself to the utensils.
OK. I probably didn’t need a study by scholars with umlauts in their names to make my point, as much as I admire their work. Contemporary dishwashers use only six gallons of water per load, while the EPA’s Energy Star models require only four. Even the older dishwashers used only around 12 to 15 gallons.
To scientifically determine if your husband is one of those very special guys who can outperform a machine, you should challenge him to wash the equivalent of a machine-load of dishes, keeping the sink drains closed, and measuring the total amount of water consumed during the operation. Please note, however, that this procedure is not entirely reliable because it will depend on an honest effort to duplicate his customary dishwashing technique. Since he will know that his efficiency is under scrutiny, he may attempt to get by with far less water than he normally would. So you may never be able to accurately determine his water consumption. But think of the new dimensions of mystery this might create in your relationship.