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Nearly 382,000 customers have signed up for Xcel Energy Inc. programs that allow the utility to control central air conditioning on the hottest days for discounted energy bills during the summer.

The Saver's Switch program allows Xcel to install a switch that turns central air conditioners off and on for short periods during peak times for energy use. In return, customers save 15 percent off of their electric energy charges from June through September. The switch typically activates when the temperature climbs to 90 degrees or higher, often in the late afternoon and early evening when many participants aren't home or are barbecuing in the backyard. The switch is activated for 15 days at most. Customers can also enroll their hot water heaters for an additional year-round discount.

In tests of the program, Xcel spokesman Tom Hoen said that on average, the temperature rises one degree when the switch is activated, and most customers don't notice because the fan stays on, circulating cool air throughout the house. Yet participation in the 20-year-old program isn't growing much. Last year, 352,000 households and 14,000 small businesses signed up for the program. This year, 364,000 households and 15,000 small businesses have joined -- a combined increase of 3.6 percent. Roughly a quarter of the company's 1.6 million residential and business customers in the Upper Midwest have enrolled.

Of course, not everyone has central air; Xcel could not say how many of their customers cool down with window units, fans, or cold showers.

The amount of energy saved from Saver's Switch and the Electric Rate Savings program -- which encourages commercial and industrial customers to take steps to reduce energy use -- can power 790,000 homes all summer long.

Enroll online at or call 1-800-895-4999 (for residential customers) and 1-800-481-4700 (for businesses).

Kara McGuire • 612-673-7293