PINE MOUNTAIN — Shareholders on Wednesday peppered Southern Co.’s chief executive officer with questions about what they see as the energy giant’s reluctance to use renewable fuels, especially in the wake of cost increases at its new coal-to-gas power plant in Mississippi.

“We feel like the Southern Co., instead of embracing the future, is trying to drag us back to the 1870s with all this coal and should be doing something to promote solar,” said Linda St. Martin, a Gulfport, Miss., resident and president of Mississippians for Affordable Energy.

St. Martin and other shareholders from Georgia, Alabama and Florida pressed Southern officials about adding more solar to its electricity grid at the company’s annual shareholders meeting at Callaway Gardens.

Tom Fanning — chairman, president and chief executive officer of the once coal-dominated Southern — said the company has invested in wind and solar energy. He defended his company’s decisions by saying that utilities should have a mix of nuclear, coal, natural gas and renewables to make sure the lights stay on at a rate that’s affordable for consumers.

“Listen, I’m very bullish on renewables,” Fanning said. “Where renewables make sense for our customers, we do them.”

Southern’s wholesale power unit has invested in solar projects outside of the company’s Southeast territory as part of a partnership with Ted Turner. In Georgia, Georgia Power has plans to boost the amount of solar it distributes to its customers tenfold over the next few years.

Georgia Power recently agreed to buy wind power from Oklahoma. Its sister utility, Alabama Power, has deals to buy wind energy from Oklahoma and Kansas.

For environmental groups such as the Sierra Club, those deals are not enough.

“As a customer, I want you to continue big bets on solar, wind and energy efficiency to make Southern Co. a real clean energy leader in the U.S.,” Seth Gunning, an organizer with the Sierra Club’s Beyond Coal campaign, read from a petition containing 2,500 signatures.

Southern’s four utilities once got more than 70 percent of its electricity from coal. Now, they get around 35 percent. Federal environmental regulations have pushed the company to close several coal and oil-fired units or convert them to run on natural gas.

Southern’s Mississippi utility, Mississippi Power, is building a new-generation power plant that converts coal to natural gas. The company recently revealed that cost of the project has increased 19 percent to $3.42 billion. Consumers will pay for some of those increases; the company is absorbing $540 million.

The cost overruns led Mississippi Power President Ed Day to abruptly retire Monday.

An unwavering Fanning called the Kemper project a “very attractive economic proposition for the state.”