by gg3 » Fri 07 Jul 2006, 09:14:18
I've been working on appliance efficiency issues for a while; good to see you starting topics on this.
Energy Star ratings are useful for competitive comparisons, but they embody certain assumptions that may not match your actual usage patterns. For certain appliances, the unit is on continuously all year, for example refrigerators, so the ratings will more closely match actual results for all users. For others, washers and dishwashers among them, energy and water usage can vary widely depending on how you use them, so the ratings are best used for competitive assessments.
For example, in washing machines, length of cycle, water temperature, whether or not you use the sanitize function (if it has one), and of course how many loads you wash each week.
What I find more useful for washers and dishwashers is, energy and water consumption per dry pound of laundry and specifying the cycles and settings. This figure automatically takes into account the differences in sizes of the various machines, so you have an apples-to-apples comparison. It also requires that you measure the actual power usage, for example with a Kill-A-Watt power monitor (about $35 retail).
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Washing machines, interestingly enough, are not big energy consumers, as long as you're not using the internal water heater (if your machine has one). The internal water heater is of course useful for sanitizing, by raising water temperatures to (depending on the model) somewhere between 160 and 200 degrees Fahrenheit. This is a good option to have for families with kids and for shared households with more than two adults, but it's not essential (e.g. in a bird flu pandemic you can wash your whites with bleach and then dry everything at high temps in the dryer).
The largest energy consumer for househould laundry is the dryer, so if you can either reduce drying time or use a clothes line, you've automatically saved a large amount of the total energy consumption for laundry. The way to reduce dryer time is by using a washer that has a high-speed spin option: the faster the spin the better, since removing water from fabric via centrifugal force (spinning) is far more efficient than removing it via heat (tumble drying).
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The most efficient washer I've seen, and I have one, is the Danby DTT-420 twin-tub. This comes in at 0.01 to 0.02 KWH per pound of laundry, with figures toward the lower end more common. For example a 6 pound load will typically register 0.07 to 0.08 KWH: about the same as a 60-watt incandescent light bulb left on for a little more than an hour. (Standard top-loading washers can come in at about twice this figure, or the equivalent of that light bulb left on for a little more than two hours. As you can see, washing clothes, in and of itself, consumes amazingly little power considering the amount of "hard work" that's being done by the motor instead of by your muscles washing by hand.) This unit is not Energy Star rated because every cycle option is controlled by a windup timer, so there is no "standard cycle" that will run automatically from start to finish.
The way the twin-tub works is, there is one compartment with an agitator for washing and rinsing, and another compartment with a high-speed spinner for spin drying. You move the load manually from one to the other a couple of times during the cycle. Machines of this type were at one time highly popular in the UK and Europe, and are still popular in Asia, the Pacific Islands, the Middle East (water efficiency), and Australia (ditto).
For example, wash for 6 minutes, drain the wash water, move the load to the spinner (maximum 4-1/2 lbs. at a time), spin for 2 minutes, re-fill the wash compartment with clean water, rinse for 6 minutes, move the load to the spinner, spin for 5 minutes, done.
The higher electrical efficiency is because a) the cycle is not automatic, each function is controlled by a manual switch or windup timer, b) there is a separate motor for each function which is matched to the task, for example the agitator motor uses about 275 watts, the spinner motor uses about 150, and the water pump motor uses about 26, and c) the agitation function uses a clever intermittent action (clockwise, pause, counterclockwise, pause, repeat) that takes advantage of the inertia of the moving water and clothes as part of the cleaning function.
Water usage can be comparable to a front-loader if you're careful. For example, you can do more than one load in the same wash water (this was how people used wringer washers when those were common, and is still done in Australia): first wash the whites in the hottest water, then the sturdy colors as the water cools, then the bright colors as the water cools further. This is not a sanitary hazard as long as you don't have clothes with poo on them (e.g. diapers) or germs from someone who has a contagious illness.
What I do is save the final rinse water for use as wash water for the next load. Since spinning occurs in the separate spin compartment, there is no need to discharge the water from the wash compartment first. Thus, the final rinse water can stay in the wash compartment for a few days until there's another load to wash. And of course final rinse water is sanitary since it's just clear water with a little bit of lint and a little detergent (though usually I'll add a teaspoon of bleach to be sure it stays sanitary for the few days between loads).
Last but not least, the spin function is high-speed (about 1400 rpm) so clothes come out nearly dry, reducing drying time in the dryer by about half. Though in my case I use indoor clothes lines for final drying, thereby saving the very large amount of power that the tumble dryer would use.
Danby DTT-420 is available via online shopping, typically about $300 plus shipping. In some places you can get these at regular appliance stores, for example New York and Los Angeles. Maximum load size is rated at 10 lbs, but as with many top-loading compact washers, actual capacity is usually less; I find that a 6-lb. load is the practical maximum (and divides into two 3-lb loads for each spin cycle). It's very quiet when running, and compact enough for apartments. The tradeoff for high efficiency is that you have to manually move the clothes back and forth between wash compartment and spin compartment, but this is hardly an inconvenience compared to the benefits. And the design is simple enough that there should be very little cause for repairs over the years.
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What I'd like to see here, are results from other folks using a Kill-A-Watt meter to measure the power consumption of their own washers (and other appliances), and specifying the settings they are using (e.g. wash cycle options).