NIPSCO wants to add nearly 1,100 megawatts in electricity production capacity to its Northern Indiana operations.

The company is looking into a $539 million purchase of two natural gas power plants to compliment its three coal power plants, shoring up its generating capacity for the next 20 years.

NIPSCO is seeking approval from the Indiana Utility Regulatory Commission to purchase the two existing power plants, located in Whiting and Terra Haute.

The Whiting facility is owned by Whiting Leasing LLC and Whiting Clean Energy Inc., which are both owned by NIPSCO's parent company, NiSource. The Terra Haute plant is owned by Sugar Creek Power Co. LLC.

The purchase is part of a long-term energy plan NIPSCO filed with state regulators last month that also includes the purchase of wind energy.

NewEnergy Associates, the independent consulting firm that worked on the plan, recommended the purchase of the two plants, and also recommended a fair purchase price for the Whiting plant.

Both plants use combined-cycle natural gas turbines to produce their power, a technology that results in greater efficiency, lower cost and lower emissions than a traditional natural gas plant.

Large combustion turbines, operating much like jet engines, initially burn the natural gas to create electricity. The heat produced from this combustion cycle is then captured and used to create steam in the second cycle, driving steam turbines to create still more electricity.

NIPSCO already supplements its power needs by purchasing electricity off the open market. It is looking to expand its capacity in the face of population and economic growth, as well as an expected requirement that it operate at an average of 15 percent below full capacity. It currently operates at an average of 3 percent below full capacity.

NIPSCO spokesman Nick Meyer said that, in the long run, the cost of purchasing the two plants would be less than continuing to buy power off the open market.

The cost of the purchase will ultimately be passed on to ratepayers, though Meyer said it has not been decided how much of it will be passed along.

Contact Erik Potter at 648-3120, or epotter@post-trib.com