The Dishwashing Debate

Power to the Peeples is an exclusive Earth911 series written by Bob Peeples, our resident chemical engineer and Program Manager of Earth911’s sister site Beaches911. Bob combines his extensive knowledge of the environment and how things work with an off-the-cuff sense of humor.

So people often wonder which is more eco-friendly: washing dishes after each use by hand or waiting for a full load and using the dishwasher. This is a big question, so let’s break down the factors at play and see if we can come up with a solution.

In what is called a “Life Cycle Assessment,” you would first consider the energy and pollution costs to the environment of manufacturing a dishwasher, but for argument’s sake let’s say you already have one.

So, it comes down to method in the end. Dish washing should avoid running water, so the answer is different if you don’t have two sinks. If you are like my mom, and nearly wash everything before placing it in the dishwasher, then you are doubling your impact.

If you have two sinks for hand washing and rinsing, and don’t wash your dishes before placing them in the dishwasher for “sterilization,” it comes down to two factors: comparing the dishwasher and water heater energy uses, and their water uses.

• Energy: If your dishwasher doesn’t use an on-board water heater, the hot water costs roughly the same (dishwashers do use slightly hotter water because their hands don’t scald). Figuring that as a minor factor, the dishwasher loses here—especially if you use the heater during the drying cycle. Either way, the pump eats up energy that your arms could otherwise provide.
• Water: This one should be a fairly easy math problem. If you have a relatively new dishwasher, you should be able to find the water use per cycle from the manufacturer. Balancing that against the number of sinks full of water it takes to do the same load gives you the answer. Hopefully, you don’t run the dishwasher for two cups of morning coffee.

That brings up another point: if you accumulate a small number of dishes each day, the hose from the discharge pump of the dishwasher to the sink drain sits stagnant that entire time. This can lead to the end of the wash cycle smelling up the kitchen like there is a feedlot in your sink. Life Cycle Assessment must also consider quality of life. While we are on the subject of quality of life, you would want to consider your time involved. Loading the dishwasher and sitting down to watch Heros not only uses more electricity to run a TV, but you forfeit that important “you wash and I’ll dry” quality time with other members of your household.

I know this sounds all too complicated. Please consider it an example of the elements that you need to consider in any of these studies, and how personal the results can become. Environmentalists like myself can pontificate all that they like, but the reality is that there is never a simple or universal answer—they are almost always personalized.

If you have ever asked this question in the first place, you are off to a good start because you are looking at it based on your own situation. No gross generalizations that I can share can do better than that.