“Always make sure the dishwasher is full before running it” is one of those mom-isms that subconsciously runs through my head each time I’m in the kitchen. It goes hand-in-hand with Don’t stand directly in front of the microwave and A watched pot never boils. But how much water do you really save by doing it?
With increasingly water-efficient dishwashers, how much water does dishwashing really take? What about compared to hand-washing? Is one more water-efficient than the other? Here’s what we found.
The average energy-efficient dishwasher uses four to six gallons per cycle, while the average dishwasher uses six gallons of water per cycle. This number is a fraction of what it used to be; even 15 years ago, dishwashers used around 13 gallons per cycle. While dishwashers vary in how many dishes they can fit and how efficiently they’re loaded, Energy Star defines a full-sized dishwasher as one that “has a capacity greater than or equal to eight place settings and six serving pieces” or, in layman’s terms, the aftermath of a serious dinner party.
Washing by hand
By some estimates, kitchen sinks spew about two to five gallons of water per minute. If you’re letting your sink run the entire time you’re washing dishes, you’ve already used the same amount of water as a dishwasher after two minutes. And as one European study estimated, this number could be higher. After watching over 100 participants hand-wash dishes, they discovered that people employed a variety of methods, but used, on average, about 13 gallons of water to wash the same number of dishes that could fit into a large dishwasher.
For hand-washing to be more efficient, you’d have to be able to wash everything in under two minutes with the water running the whole time, or fill your sink with about four gallons of water and wash your dishes in that. (This is what our founder Amanda Hesser insists is the best way to wash dishes.) Nota bene: Many kitchen sinks have capacities of up to four or five times that. So just fill up as much as you need.
A cheat sheet
Estimate how much time it would take you to wash all of your dishes:
If it’s two minutes or less for the entire batch: Hand wash.
If it’s over two minutes: Use the dishwasher.
The best option: If you have enough plates and cutlery to do so, put your dishes in the dishwasher each night, then run it when it’s completely full. Alternatively, fill your sink with a few gallons of soapy water and use that to wash all of your dishes.