By Ted Caddell

Exelon Generation is adding another 2,000 MW of fossil generation to its fleet in Texas, which will bring the company’s total generation in ERCOT to nearly 6,000 MW.

The company announced Monday it was investing more than $500 million in four gas and two steam turbines to build combined-cycle plants at two of their existing sites.

In addition to using the most fuel-efficient technology, the plants will be air-cooled, rather than water-cooled, a big plus in drought-threatened Texas. The turbines will be General Electric H-class models, which GE says will allow more than $8 million in fuel savings per turbine a year.

French company Alstom is providing the heat recovery steam generators. Earlier this year, GE agreed to buy the power arm of Alstom for $16.8 billion.

It will be the first use of the new GE turbines in the U.S.

“What we see is a clean-energy future that includes this kind of new technology, which uses little water and produces few emissions while generating electricity at a very low cost,” said Ken Cornew, president and CEO of Exelon Generation.

The new combined-cycle plants are to be built at Exelon Generation’s Wolf Hollow site in Grandbury, southwest of Fort Worth, and the Colorado Bend plant in Wharton County, southwest of Houston.

Exelon Generation currently has six generating stations in Texas with a combined output of about 3,700 MW. It has wind farms generating an additional 281 MW, for a total of nearly 4,000 MW.

The two new plants will boost that total to nearly 6,000 MW. Exelon said it would start construction of both plants in 2015 and expects both to be in service by 2017.