US utility, FirstEnergy have announced it is retiring six coal fired power plants, including four in Ohio, because of stricter federal anti-pollution rules.

With the company facing more stringent pollution limits and competition from suddenly abundant and relatively cheap natural gas FirstEnergy decided it wasn't worth upgrading small, old power plants to comply with new air and water standards.

Over 200 coal fired units have been mothballed across the US during the past three years, most of which were built in the middle of the previous century and until recently were largely exempt from the toughest provisions of the federal Clean Air Act.

The closings were triggered by the U.S. Environmental Protection Agency’s new Mercury and Air Toxic Standards (MATS), which were finalized Dec. 21.

The utility is expecting to spend between $2bn and $3bn on improvements to its remaining coal fired plants to meet the federal rules.

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