Washing machine motor efficiency and the Law of Unintended Consequences

Higher motor efficiency is a Good Thing – It’s unlikely that any design engineer ever said, “Gee, if only I could find a really inefficient motor for my next design.” When I was working on an article this summer on designing with energy-efficient permanent magnet motors and how their use is expanding in home appliances, washing machines were the poster-child application that all control electronics vendors and motor manufacturers used. However, most people buy washing machines not because they are energy-efficient, but because they want to get their clothes clean, and according to Consumer Reports, many of the new washing machines are pretty poor at cleaning clothes.

According to Consumer Reports, “As of January [2007], the U.S. Department of Energy has required washers to use 21 percent less energy, a goal we wholeheartedly support. But our tests have found that traditional top-loaders, those with the familiar center-post agitators, are having a tough time wringing out those savings without sacrificing cleaning ability, the main reason you buy a washer.”

Happily, the new front-loading washers, which universally use permanent magnet motors, meet the energy efficiency standards and do a good job of cleaning clothes without destroying them. Unhappily, they cost in the neighborhood of $1000 for a washer/dryer set. And most consumers seem to prefer top-loaders, both out of familiarity and because they’re less expensive. But the top-loaders gave up cleaning ability when they gained energy efficiency, and most consumers will probably stay with the less expensive, less effective top-loaders.

Remember the water-conserving toilets that many states started requiring about 30 years ago? The joke was, yeah, they theoretically save water but you have to flush everything twice, which kinda defeated the purpose. Are washing machines really energy efficient if you have to wash your clothes twice?

OK, cheap shot. I hope the water-closet analogy is correct, because it didn’t take too long before plumbing designers got it right: Today’s water-conserving toilets and shower heads work just fine. But here’s a hint: you might want to hold off a few years on purchasing a top-loading washing machine.