Raleigh, N.C. — Progress Energy (NYSE: PGN) said Tuesday it will shut down three more coal-fired power plants by 2017 and will look to build more natural gas-fired plants in the future.

The plants to be closed are not equipped with “scrubbers” that remove pollutants. Some plants to be closed are more than 50 years old. Progress Energy officials said it would be prohibitively expensive to add the high-tech gear to the plants.

The facilities affected are near Wilmington, Moncure and Lumberton, affecting a total of eight units, according to a filing with the North Carolina Utilities Commission.

Coupled with the recent decision to close a similar plant near Goldsboro, Progress Energy said it would reduce its coal-fired production capability by 1,500 megawatts, or nearly 30 percent.

The Utilities Commission has already approved construction of a $900 million gas-fired plant at the Goldsboro site.

“This is a significant commitment to clean air in our state and a major down-payment on our company’s carbon-reduction strategy,” Bill Johnson, chairman and chief executive of Progress Energy, said in a statement.

“Within seven years, we expect to retire nearly one-third of our coal fleet in North Carolina. We are aggressively pursuing a balanced solution for meeting future energy needs, including clean technologies and energy efficiency, while continuing to ensure that electricity remains available and reliable.”

The three units at the Wilmington site will be shut down by 2014, and Progress Energy plans to seek approval from state regulators to build a 600-megawatt gas-fired plant at the site.

The five units in Moncure and Lumberton will be shut down between 2013 and 2017. Officials said they might convert the sites to wood waste or other renewable sources of fuel, but they also are evaluating the sites for possible gas-fired plants.

Progress Energy will continue to operate three coal-fired plants in North Carolina after 2017.

The Raleigh-based utility has invested more than $2 billion to install state-of-the-art emission controls at the Roxboro Plant and Mayo Plant, both in Person County, and the Asheville Plant in Buncombe County. Officials said emissions of nitrogen oxides, sulfur dioxide, mercury and other pollutants have been reduced significantly at those sites.