Since electric competition took off on Jan. 1 in Peco Energy Co. territory, more than 260,000 customers have switched suppliers, according to the utility.

About 16 percent of Peco's 1.6 million customers, including most of its large industrial customers, have switched to alternative suppliers, according to Cathy Engel Menendez, spokeswoman for the Philadelphia utility.

Nearly half the power distributed through Peco's system is now supplied by alternative suppliers, she said.

Competition has taken off more quickly than anticipated. Nearly 50 suppliers serve Peco customers, including 36 that target residential customers. Some are offering discounts of 10 percent or more, saving a typical residential customer $90 a year.

Under the state's electric choice law, customers have the option to buy the electricity from a competitive supplier. For customers who don't shop, Peco purchases electricity and passes it along without markup.

"This is a win-win for our customers," Denis O'Brien, Peco's president, said in a statement. Peco remains the distribution company for all customers and collects a fee regardless of whom customers choose as their supplier.

In the new environment, Peco's default rate for customers who do not shop is adjusted every three months to reflect market conditions.

The default rate - also called the price to compare - will increase slightly on Friday from 9.92 cents per kilowatt hour to 9.99 cents.

Customers who switch could save even more this summer, said Irwin A. "Sonny" Popowsky, the state's consumer advocate.

Under Peco's tariff, residential customers in June will pay 11.2 cents per kilowatt hour for monthly usage exceeding 500 kilowatt hours - that applies to most customers with central air-conditioning. Customers who sign up with alternative suppliers do not pay the surcharge.