While there's a perception that hand washing dishes conserves water and electricity, according to EcoHome Magazine, the opposite is true. If you use an efficient dishwasher with a high Energy Star rating, you will, on average, use less water and energy than you would if you hand washed the dishes. In addition, dishwasher water temperature, which is generally hotter than tap water, does a better job of sanitising dishes.
According to the website Seventh Generation, the average Energy-Star-rated dishwasher uses 4 gallons of water; the average hand-washing dish washer uses 6 gallons. While a 2-gallon difference isn't much, if the average household runs the dishwasher once per day, the difference is 1,460 gallons (dishwasher) versus 2,190 gallons (hand washing) or 730 gallons. Based on that difference, you could run your automatic dishwasher each day for six additional months.
In a study conducted at the University of Bonn, 70 dishwashers each washed 12 place settings of dishes. Noting that an energy-efficient dishwasher uses 1 to 2 kWh per load, comparative results were significant. Usage among manual dishwashers ranged from 3.5 kWh up to 16 kWh based on personal styles and country of origin. According to the study, 1 kWh is the energy needed to heat cold tap water up to 15 Celsius, the temperature used to wash dishes. When a standard-sized, new-model Energy Star-rated dishwasher uses less than 324 kWh a year, it makes no sense to stand firm to the idea that hand washing dishes conserves water and energy.
Dishwashers manufactured before 1994 used on average 10 gallons per cycle, as reported by Energy Star. The perception that a dishwasher is a water hog perhaps stems from older, less conserving models. With this in mind, if you have an older dishwasher, it might make sense to upgrade to a more efficient model.
Increasing Dishwasher Efficiency
Use the dishwasher only when it's full but don't over fill it. To assist your dishwasher's cleaning effectiveness, scrape plates and allow the dishes to soak in a sink of soapy water. By pre-soaking in your sink, you can avoid using the "Pre-Rinse" cycle on the dishwasher. Finally, set your hot water heater to 48.9 degrees C. While a dishwasher's water temperature is optimal at 60C, you can still achieve sanitary cleaning at 48.9C and you save energy.
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- EcoHome Magazine: Dishwashers Combine Energy Efficiency, Water Conservation and Premium Cleaning
- Seventh Generation: Ask Science Man
- EnergyStar: Dishwashers
- Planet Green: Maximizing Hand Dishwashing Efficiency in 5 Easy Steps
- Consumer Energy Center: Dishwashers
- Slate: Is a Dishwasher a Green Machine?