Q: Dishwasher or hand washing?
Asked by Kim Stone, JD ’96, Sacramento, Calif.
My mom recently splurged on a kitchen remodel. She installed granite countertops, a five-burner cooktop, a convection oven—and a dishwasher that sterilizes cutlery to near-surgical standards. Understandably, she gripes at me when I hand wash my dishes in her home. I've tried to explain that I'm accustomed to the balmy California climate, and thus require frequent contact with hot sudsy water when I return to the far north (Portland, Ore.) for a visit. But although it's bad news for my cold fingers, there are sound economic and environmental reasons for me to let Mom's beloved Bosch handle my cereal bowl.
The first reason is water use. Modern, efficient dishwashers use five to six gallons of water per full load of dishes, or about 1,000 gallons per year (assuming one load every one to two days). According to the federal government's Energy Star program, in order to hand wash all those dishes, you'd need another 5,000 gallons per year, or a total of around 30 gallons per load. In fact, just pre-rinsing your dishes in the sink before putting them in the dishwasher adds about 20 gallons per load. A standard bathtub holds roughly 24 gallons of water—so let the dishwasher handle the dirty dishes, and treat yourself to a weekly soak in the tub.
Heating water takes energy, which means that by cutting back your hot water use, your dishwasher also reduces the total energy consumed by your home water heater (see Nitty Gritty for more tips on improving water heater efficiency). An Energy Star-certified dishwasher uses around 300 kWh of energy per year or less, assuming that you run a full load every one to two days. Heating all the water required to hand wash an equivalent stack of dishes could consume up to 650 kWh of electricity per year. That 350 kWh difference is roughly equivalent to the energy demanded by a 60-watt light bulb left on for 14 hours a day, every day, all year long. In short, by switching from hand washing to a dishwasher, you'll achieve about the same energy savings as you do by turning the light out when you leave a room.
If you're currently hand washing and are interested in a good long-term economic investment, consider having a dishwasher installed. Energy Star estimates that making the switch from hand washing can reduce your utility bill by about $40 per year. Basic Energy Star dishwashers cost about $300, meaning that you could see complete payback in less than eight years—well within the machine's expected 12-year lifetime. As noted in the Nitty Gritty, your energy savings will also easily offset the energy used to manufacture the dishwasher, perhaps even before the financial investment is paid off. You might also think about upgrading an older dishwasher, since those built before 1994 are significantly less efficient than new models. In either case, visit the Energy Star website for product ratings, and note that the most efficient dishwashers on the market use about half the energy and one-fourth the water of models that just meet federal standards. More proof that Mom knows best—Bosch dishwashers score especially well on water and energy efficiency.
Keep other environmental impacts of dishwashing in mind, too. Many dish soaps and detergents contain phosphates, which can deplete oxygen levels and cause fish deaths in lakes and streams after they head down your drain. Phosphates will be listed as an ingredient on some dish detergents: Leave those on the shelf, and look for products that contain Zeolite, a more eco-friendly alternative used by some manufacturers. Also be sure to choose products free of chlorine, which is highly reactive and can have measurable negative effects on human and environmental health even in small quantities.
One final thought—your best option could be to create fewer dirty dishes in the first place. Just be sure to fill your dishwasher before you run it, or use a half-load setting to keep your water and energy use per dish low (see the Nitty Gritty for more on making the most of your dishwasher). Try serving food from the pots and pans you cooked in, and resist the urge to give everyone a separate salad fork. Better yet, take a trip back to childhood—throw everything in one bowl (pureeing optional), eat with your fingers, lick it clean and call it a day.
Kate Johnson, '10, plans to receive her master's degree in Earth Systems in 2011.
