Progress Energy said it will shut 11 coal-fired power plants at four sites in North Carolina, US, by 2017.

The company, which has bowed to environmental pressure said it will replace the capacity with gas-burning units.

The action is part of a trend in which utilities are shutting down older, smaller coal-burning units and adopting cheap natural gas as a “bridge fuel” to fill the gap until the 2020-to-2030 time frame, when nuclear and renewable energy will play a larger role in the energy mix.

The power plants facing retirement in North Carolina were built between 1952 and 1972 and thus will be of retirement age by 2017.

They constitute 30% of the utility’s North Carolina coal capacity and, in an earlier era, might have been refurbished, writes the Wall Street Journal.

Progress Energy said it hopes to build two nuclear power plants in the next decade at an expected cost of $16.5 to $17bn.