The nation's largest public utility has voted to close six coal-powered units in Alabama and replace two more in Kentucky with a new natural gas plant.

At a Thursday meeting, Tennessee Valley Authority CEO Bill Johnson said increasingly stringent environmental regulations and flat power demand have made it necessary to rethink how the utility generates power.

Senate Republican Leader Mitch McConnell met with Johnson last month to seek continued operation of the coal-burning Paradise Fossil Plant in Drakesboro, Ky. One coal-fired unit will remain there.

The board also voted to close all five units at the Colbert plant in northwest Alabama and one of two remaining units at the Widow's Creek plant in northeast Alabama.

Board members from Alabama and Kentucky said the closures were difficult but necessary.