Is handwashing your dishes better? New study says no

Washing dishes by hand takes longer and hurts the environment. A recent University of Bonn study (here) shows that hand washing dishes uses more energy, more time, and significantly more water than using a dishwasher. The German study settled on 12 place settings as the average number of plates cleaned in one day (a family of four that has three meals), including utensils and other cooking tools. These dishes were soiled and left out for two hours in order to approximate a difficult, but not overly complex cleaning job. To clean the dishes, appropriate test subjects and cleaning supplies had to be found. Tourists who were visiting Bonn from a total of seven countries volunteered for the study, and cleaning supplies from all over Europe were brought in to ensure that people were able to clean like they would at home. In order to properly quantify their results, the University of Bonn researchers broke “hand washers” down into three separate categories: super dishwashers, dishwashing economizers, and care-free dishwashers. The “super” dishwasher is focused mostly on the cleaning process itself, and therefore does not focus on conserving water or detergent. Dishwashing “economizers” focus on saving water or detergent at the expense of cleaning, though the study notes that attempts to conserve on resource usually results in the squandering of another. Finally, “care-free” dishwashers (a category that researchers didn’t expect) simply don’t care about cleanliness or conservation. This group is characterized by constantly leaving the tap running, even during the drying process. Here’s where things get interesting: the amount of water used by hand dishwashing varied quite a bit, but the average fell between 30 and 100 liters (about 8 and 26.5 gallons, respectively). Compare that to dishwashers, which average around 15 liters (around 4 gallons) per load and it is easy to see how quickly that discrepancy can add up over time. In terms of energy used, hand washing used 2.5 kwh (to heat the hot water) while a dishwasher only uses between 1 and 2 kwh. This study shows fairly conclusively that hand washing dishes can take its toll on the environment; especially if one is not careful with the amount of water and detergent they end up using.