Customers of Florida's largest utility will soon start paying more on their power bills. State regulators have approved changes requested by Florida Power and Light that will raise the average residential bill nearly five dollars a month. The increase takes effect in January. A spokesman for FPL pointed out that the utility still has the lowest rate among the state's 55 electric utilities. One of the main reasons for the rate change is an increase in how much t he utility pays for fuel. Fuel charges are passed on directly to consumers with no mark up.