Some cities challenge residents to lose weight or become more fit.

But Alpine, American Fork and Lindon are doing something different: They want residents to start using cleaner electricity.

Between now and Sept. 30, the three cities are taking a challenge from Rocky Mountain Power to obtain 5 percent of the community purchasing renewable energy credit through the utility's Blue Sky program.

"It provides an easy, affordable way for customers to support renewable energy beyond what the company is doing to generate renewable energy on behalf of all customers," said Jeff Hymas, a Rocky Mountain Power spokesman.

In the Blue Sky program, power customers can buy clean energy credits in blocks of 100 kilowatt hours for $1.95 a month.

The power company then purchases the same amount of energy from wind farms in Wyoming or other renewable energy producers. Rocky Mountain also purchases Blue Sky power credits from the Spanish Fork Canyon wind farm.

The program doesn't give the customer a discount on his electric bill. He still has to pay for the electricity he uses, along with the clean energy credits as well. The goal: Give people a way to reduce their dependence on coal- and gas-fired power plants and foster environmentally friendly power production.

A customer seeking to offset their entire electric use with renewable energy would have to buy 800 kilowatt hours of credits a month.

To encourage residents, each of the three cities has agreed to purchase 700 kilowatt hours of credits -- almost enough to power the average household for a month.

April Naidu, Alpine's planner and Blue Sky liaison, said some residents already participate in the program, but the city plans to contact others through its Web site and city notices. She said Rocky Mountain Power has expressed interest in getting a booth at Alpine Days to encourage participation in the program.

The city has also helped foster renewable energy by passing an ordinance allowing residents to put up their own wind turbines in their back yards to generate household electricity.

Ott Dameron, Lindon's city manager, said his community doesn't have to go too far to meet the challenge.

"We already have 3 percent signed up, and to reach 5 percent ... that's a couple hundred people," Dameron said.

The city plans to put notices in utility bills, as well as use flyers and banners provided by Rocky Mountain Power. dmeyers@sltrib.com