CHARLOTTE, N.C., June 17, 2013 /PRNewswire/ -- Duke Energy (NYSE: DUK) continues to move up the solar energy charts. (Logo: http://photos.prnewswire.com/prnh/20130322/CL81938LOGO ) In the recent Solar Electric Power Association (SEPA) utility rankings, Duke Energy was ranked eighth among holding companies in the United States for total solar capacity. Among individual utilities, Duke Energy Progress in North Carolina and South Carolina was ranked eighth nationally for its annual increase in solar. You can view the entire report here. SEPA reported that Duke Energy's regulated utilities have 183 megawatts of capacity available for its customers. That figure is roughly half of the capacity of the company's coal-fired Lee Steam Station in South Carolina. "These rankings reflect the efforts Duke Energy has made to incorporate solar energy into our generation mix in the six states we serve," said Rob Caldwell, vice president, wholesale power and renewable generation. "Solar will continue to be a growing part of our energy mix. However, due to the variable nature of solar, Duke Energy will still need generation capacity fueled by nuclear, coal and gas to meet our customers' energy needs." In Duke Energy's regulated areas, the company purchases most of its solar capacity from other companies to comply with regulatory guidelines set forth by the various states. "As solar becomes a bigger part of our energy mix, we will need to make sure the rules in our regulated states treat all customers fairly – and that solar is a sustainable part of our energy portfolio," added Caldwell. "Widespread use of solar is still new in our area and there are complexities that need to be addressed." Outside of its regulated areas, Duke Energy owns more than 100 megawatts of commercial utility-scale solar capacity through its subsidiary Duke Energy Renewables.