A Duke Energy Corp. subsidiary for North Carolina electric customers has asked state regulators to let them raise residential rates by 16.6% in the coming months largely to recover their fuel costs, which it said soared mainly from natural gas prices last year. Duke Energy Carolinas serves about 2 million households and businesses in western and central North Carolina. It said Wednesday that if the request is approved by the state Utilities Commission, the typical residential customer's monthly bill would increase from $115.01 to a little over $134.11. The Charlotte-based utility emphasized such approved requests don't widen anticipated profits, but...