Efficient dishwashers can clean your dishes using less water and energy than if you try to clean them yourself. That's what the ENERGY STAR folks tell us. But is it really the truth?
I used to be skeptical. I can wash the supper dishes by hand using only four liters of water, while energy saving dishwashers use around 4 gallons to a load, plus all that energy to heat the water and slosh it around.
In this article I will share my techniques for washing dishes by hand using as little water and energy as possible. But don't forget that, for most of us, modern efficient dishwashers are a better choice than hand-washing, as long as you use the dishwasher properly.
If you observe a typical American clean dishes by hand, it's easy to see why an efficient dishwasher wins over washing by hand just about every time. Some people let the tap run continuously as they clean; some fill a sink with warm soapy water and then run cold water in the second sink for rinsing; some are continuously squeezing dish soap into a scrub brush. When you consider all the energy that is required for heating the water, manufacturing the dish soap, and even the energy for treating and pumping the water to your home, it can wind up being a lot more energy than you would guess.
When people think about the energy use of a dishwasher, they usually think of the electricity that pumps water around inside the dishwasher. They might think that they can save all that energy if they wash dishes themselves. In fact, pumping and draining uses less energy than heating the water - only 20% of the total, compared to 80% for heating when you consider the heating that takes place in your hot water tank and in the dishwasher proper.
You might think that hand-cleaning dishes would at least save you the remaining 20% of the energy used by the dishwasher. But since people usually use much more water than modern efficient dishwashers, the end result is more energy use in hand-washing than when using a recent-vintage dishwasher. (Older dishwashers use up to twice as much water as newer models, so you might outperform that old avocado-colored dishwasher!)
Energy efficient dishwashers can wash dishes with a very small amount of water by doing two things you cannot match when hand washing: Heating the water to a scalding 140F - too hot for your hands - because hot water is better at getting grease and other food residue off dishes; and circulating the water at high pressure, which blows waste off your dishes more effectively than you can hand-scrub it, consuming a very small amount of water in the process.
Where energy efficient dishwashers are less efficient is where people sabotage the energy saving features of the dishwasher, by rinsing before loading, maintaining too high a hot water tank temperature, choosing too long a cycle, using the rinse-and-hold or heated-dry features, running partial loads, and using too much dishwasher detergent.
You actually can outperform a dishwasher in terms of energy consumption. Whether it's worth your while is moot. Consider the fact that energy efficient dishwashers with an ENERGY STAR logo can do a load for the energy equivalent of at most 1.54 kilowatt hours (kwh) of electricity (including all the energy for mechanical and heat). At a typical cost of ten cents per kilowatt hour, and assuming you clean the dishes using cold water, the most you will save is around a dollar for every six loads.
And this is for a full dishwasher load - which is supposed to accommodate 6-8 complete place settings as well as 6 serving pieces. Assuming bread plate, dinner plate, bowl, cup and saucer, knife, fork and spoon, that's about 72 items cleaned, so you'll save about a cent for every five items if you wash by hand and use cold water.
But let's assume, for argument's sake, that you want to clean dishes yourself. I actually enjoy washing dishes; it's good contemplation time, plus it cleans my fingernails! How can you clean dishes by hand most efficiently? Here are my tips:
Never drain used water. After you've cleaned a load of plates by hand, or rinsed salad greens, leave the water to sit. Use this gray water to pre-rinse the dishes to remove the bulk of the food residue. That way, when it's time to wash, you'll need a lot less water.
Never let the tap run for extended periods. Turn it on for a few seconds at a time, only when you really need water.
Use aerators on your kitchen faucet. You can rinse dishes with much less water using a faucet aerator, which injects a stream of air into the water.
Use cold or just lukewarm water. Where I live in the tropics, no one cleans dishes in hot water, although of course the cold water comes out at a pleasant 70F. This just goes to show that you can, at the very least, clean in lukewarm rather than hot water.
Start with an inch of warm water in the sink. Wash dishes in that, and rinse in your second sink with cold water. Otherwise stack the dishes after cleaning, and then rinse them all in cold water when you're done the wash.
Just like your mom taught you, begin by cleaning the cleanest dishes - glasses, cups, cutlery, plates, and finally pots and pans.
Using these tips I can wash all the dishes from a four person meal in less than a gallon of fresh water. But is it worth all the effort? And how many people can actually outperform the efficiency of a good, late model dishwasher?
If you think you can outperform a new dishwasher, here's some research that modern efficient dishwashers not only clean dishes with less energy, water and detergent than people do, but also get the dishes cleaner.
A German study asked over 100 subjects to wash 12 place settings of dirty dishes. Each volunteer was given the run of a kitchen and observed by video; energy, water and dish soap use were tracked. The dishes were then inspected for cleanliness using an international standard for clean dishes. The same test was repeated with energy saving dishwashers.
The efficient dishwashers consumed 15 liters of water and 1-2 kwh of energy to clean 12 dinner place settings, while only two of the 113 subjects used under 20 liters of hot water. (Forty of the human subjects used over 100 liters of water each!). However, 70 of the subjects did manage to use 2 kwh or less of energy - and a quarter of the test subjects used 1 kwh or less.
The way I read the results of this study, it is possible to match the efficiency of modern efficient dishwashers, or even beat their performance slightly. But the energy saved is so small that the extra effort doesn't seem worthwhile. The human hand-washers took at least 40 minutes to do the load, while the energy efficient dishwashers needed only 15 minutes of human work for loading, starting, and unloading. Considering that the US government rates dishwasher efficiency assuming 215 loads per year, a typical hand washer would be adding about 89 hours of work to their year. That's more than two weeks of 9-to-5 work out of your life!
You are probably better off to save that time and look at other things you can do to conserve energy. Imagine how efficient your house would be if you set aside an extra 89 hours a year towards caulking, weather-stripping, insulating, sealing air leaks, and changing light bulbs to more energy efficient lights. Or how much more relaxed you'll be by using your energy efficient dishwasher. You just earned two extra weeks of free time!
Autor:
Robin Green Robin GreenLevel: Platinum
Robin Green has been obsessed with energy efficiency since he built a wind generator at the age of fifteen. He currently runs Green Energy Efficient ... ...
Robin Green runs Green-Energy-Efficient-Homes.com, a website that helps people save energy in their homes. For more on saving electricity while washing dishes, see Energy efficient dishwashers on Green Energy Efficient Homes
Added: March 20, 2009
Source:
http://ezinearticles.com/
Posts
