Several advantages over conventional modelsConventional dryers heat air inside a drum to drive moisture out of clothes. With most models, the moist, humid air is vented to the outside, which also takes some conditioned air from inside the house with it. So there’s a double energy penalty — high power consumption to run the dryer, and additional power to heat or cool inside air to replace what’s been lost.In Whirlpool’s heat pump clothes dryer, a refrigeration loop condenses the moisture picked up from the clothes and routes it to the same drain used by the clothes washer. Heat from the process is recirculated back to the drum. While the dryer has to be connected to a drain, it is not vented to the outside, so it can be installed in more places than a conventional dryer can.The design has won the EPA’s Emerging Technology Award, and earlier this month picked up an Innovation Award at the Consumer Electronics Show in Las Vegas.According to Whirlpool, the dryer uses up to 73% less energy in its “Eco” mode when compared to a pre-2004 conventional dryer. The Super Efficient Dryer Initiative estimates that heat-pump clothes dryers are 50 percent to 60 percent more efficient than conventional models.The HybridCare has three speed settings — Eco, Balanced and Speed — with average drying times of about 60 minutes, according to the company. A 1,300-watt heating element kicks in when the Speed cycle is selected. The company also says the dryer operates at lower temperatures than a conventional dryer, so it’s not as tough on delicate fabrics.It’s not clear whether the LG dryer is vented to the outside or taps into the washer drain like the Whirlpool model does. Those details aren’t posted at the company’s web site, and the company didn’t respond to queries. Clothes dryers are the energy hogs of home appliances, accounting for 6 percent of total residential energy use and costing U.S. consumers $9 billion a year in power bills. Dryers use more electricity — an estimated 900 kilowatt hours a year — than either a refrigerator or a clothes washer.Homeowners in Europe have long had access to dryers that use heat-pump technology instead of electrical resistance elements or gas burners to dry clothes. And now two manufacturers, Whirlpool and LG, are rolling out heat-pump clothes dryers for U.S. buyers.Whirlpool’s 7.3-cubic-foot HybridCare clothes dryer is similar in size to conventional dryers on the U.S. market (although larger than most European models). The HybridCare comes with a suggested retail price of $1,799 in white, more than four times the cost of a base model Whirlpool available at Lowe’s.LG Electronics says that its Eco Hybrid heat-pump dryer, also with a 7.3-cubic foot capacity, was the first dryer in the U.S. to combine conventional vented drying with heat pump technology and uses about 50 percent less electricity than a conventional electric dryer. It sells for about $1,700.