An early spring heatwave across central North Carolina could increase power bills for many customers next month due to temperatures reaching 90 degrees, which hasn't been seen since 1960. The cost of maintaining homes cool is increasing as temperatures rise, and this comes at a time when many households are already seeing higher energy bills. Duke Energy, which provides about 50% of summer power bills, expects more usage due to increased use of air conditioners. The company has also proposed a rate increase, which would take effect on Jan. 1. Some customers are already trying to cut back or use alternative cooling methods to cool down.