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Old laundry habits are hard to kick. But washers have changed, so have laundry detergents and you no longer have to use hot water to get clothes clean. You'll save energy washing in cold water, and here's why.

Even though they use less water, newer washers are much better at cleaning than the top-loaders with a center agitator made 15 years or more ago.

Manufacturers have been lowering wash temperatures over the years to meet the Department of Energy’s tough energy standards for hot water use.

Heating water accounts for about 90 percent of the energy needed to run a washer, according to Energy Star, so the less hot water used, the more energy saved.

These changes meant laundry detergents had to adapt too. So we asked the folks at Procter & Gamble to explain what changed. Sales of their laundry care products account for 53 percent of the market, according to Mintel, a market research company.

Flickr / Mike Mozart "Front-loaders and high-efficiency top-loaders run normal cycles 10 percent cooler than agitator washers, and the 'warm' wash temperature in the U.S. has declined by 15 degrees over the past 15 years," says Tracey Long, communications manager for P&G's fabric care products in North America. “Traditional detergent enzymes can be sluggish in cold water so we worked to create a mix of surfactants and enzymes that deliver cleaning performance in cold water across all product lines," says Long.

Consumer Reports’ past tests found detergents have gotten much better at putting enzymes to work in removing dirt and stains at lower water temperatures, and are less effective at higher temperatures.

You'll save energy washing in cold water. When you want to brighten whites, use cold water and a bleach alternative, such as Oxi-Clean. But when a family member is sick, use hot water mixed with chlorine bleach to reduce bacteria in the bed linens and towels. The same goes for cleaning dirty cloth diapers.

Shopping for a Washer?

See our washing machine ratings of front-loaders, high-efficiency top-loaders, agitator top-loaders, and compact washers. Our washing machine buying guide is a good place to start your search. We're testing laundry detergents now and will post our results in the coming weeks.