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Set your own rates by tracking hourly prices and doing chores when electricity is cheap.

The Marynowskis cook dinner a day ahead, so at 5 p.m., a meal can be warmed in the microwave and on the table in two shakes. They're efficient working parents, yes, but they also do it to save money on their electric bill -- some $250 in savings last year. The Marynowskis are among the first of what could be millions of families saving some $7.5 billion a year in energy costs by 2010.

Utilities have traditionally charged customers an average rate for electricity -- use more and you pay more, but the price per kilowatt hour doesn't change much. Some utilities offer discounts if you use less electricity during peak demand periods -- but again, you pay a fixed (albeit discounted) rate. Now, with new, high-tech meters, families can price their electricity usage down to the hour, giving them plenty of opportunities to conserve when prices rise.

Customers who sign up for Commonwealth Edison's Real Time Pricing program get projections for energy costs a day ahead, and ComEd sends them alerts -- by e-mail, voice mail or text message -- when prices hit a certain threshold.

For example, the Marynowskis want to know when electricity costs are headed over 14 cents per kilowatt hour. On a hot day, prices can swing from 3 cents to 25 cents per kilowatt hour, says ComEd's Anne Pramaggiore. Even after paying $2.25 a month for the fancy meters, customers enjoy average savings of 9% a year, and 95% of customers save something.

Similar efforts are under way or being tested at dozens of other utilities. If one of them is yours, consider staying up late to do the laundry.

See more ways to save money on utilities.