"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 4 to 6 gallons per cycle, while the average dishwasher uses 6 gallons of water per cycle. This number is a fraction of what it used to be; even fifteen 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 terms, the aftermath of a serious dinner party.
By some estimates, kitchen sinks spew about 2 to 5 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 2 minutes. And as one European study estimated, this number could be higher. After watching over one-hundred 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 4 gallons of water and wash your dishes in that. (This is how our founder Amanda Hesser insists is the best way to wash dishes.) NB: Many kitchen sinks have capacities of up to 4 or 5 times that. So just fill up as much as you need.
Estimate how much time it would take you to wash all of your dishes:
If it's 2 minutes or less for the entire batch: Hand wash.
If it's over 2 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.
EDITOR'S NOTE: This article originally ran in April of last year. We've decided to republish it in observance of World Water Day.
What are some of your favorite water-saving dishwashing strategies? Tell us in the comments below!