Eversource Energy on Wednesday warned that customers could see natural gas heating prices rise 15 percent, costing an average of $30 a month more compared with last year. In the company’s third-quarter 2021 earnings call on Wednesday, Philip J. Lembo, executive vice president and chief financial officer, cited rising prices post the COVID-19 pandemic, forecasts of a cold winter, and supply issues as reasons for the price increase. Eversource serves 4.3 million electricity and natural gas customers in Connecticut, Massachusetts and New Hampshire, where it also has headquarters. “Overall, including the distribution charge, we expect natural gas heating bills will be up about 15 percent on average. That’s about $30 a month to the average for a typical heating customer compared to last winter. And that’s an average across our three natural gas distribution companies,” Lembo said. “While a 15 percent increase is significant it is far less than the more than 30 percent increase …