New figures released by the state Public Utility Commission show the difference between current market prices for electricity and the capped rates paid by millions of Pennsylvanians.
Rate caps expire in 2010 for PPL customers and in 2011 for customers of four other major utilities.
If the caps had expired the week of July 6, Peco Energy's residential customers actually would have seen their bill drop by almost 5 percent on average.
Metropolitan Edison customers would have seen a 26 percent jump and Pennsylvania Electric customers a 22 percent increase.
PPL and Allegheny Power already purchased power for use after caps expire, ensuring average increases of 30 percent and 11 percent, respectively.