Duke Energy Corp., the nation’s largest electric utility, says it can cut greenhouse gas emissions more than 70% in the next 15 years in North and South Carolina — but doing so could cost customers up to $58 a month. The company has drafted six roadmaps for cleaning up its energy mix. One would close Duke’s remaining coal-burning plants as quickly as possible, replacing them with new natural gas plants, along with wind and solar backed by batteries. Another would eschew new gas plants for batteries, offshore wind farms and small nuclear reactors. All would have a cost to consumers, adding between $21 and $58 to monthly electricity bills in 2035. Duke, which supplies electricity in six states, isn’t championing any particular plan, […]