Gas & Wind Dominate New Generation in 2012 But New Coal Accounts For 20% Of Total

From January to August 2012, new natural gas and wind capacity accounted for 70% of the total that began operating.  A total of 11,866 megawatts began operating, and new gas and wind plants equaled 4,636 and 3,604 megawatts respectively, according to the Federal Energy Regulatory Commission.
http://www.ferc.gov/legal/staff-reports/aug-2012-energy-infrastructure.pdf.

New wind capacity, however, will surpass new gas by the end of the year, as developers raise to finish project prior to the scheduled expiration of the production tax credit in December. America is on course to build about 10,000 megawatts of wind alone this year.

Apart from wind and gas, new coal plants were most of the remainder, 20% of the total, at 2,276 megawatts.  New solar capacity  was listed at 766 megawatts, but this number does not include the large amount of solar capacity that is distributed and not required to receive FERC approval. 

New solar capacity from all projects may exceed new coal capacity in 2012, for the first time in the nation's history. But importantly, as a result of substantially higher capacity factors, the new coal capacity will likely produce 5 to 6 times more electricity than the 2012 new solar capacity.

Rounding out the 2012 new plant capacity to date is 329 megawatts of biomass, 125 megawatts of nuclear, 105 megawatts of geothermal, 13 megawatts of oil (Hawaii??), 9 megawatts of hydro, and 3 of waste heat.

The 2012 new capacity build is lower than in 2011 at the same time.  In 2011, 14,212 megawatts of new capacity had opened by August.

America has a total of 1,153,910 megawatts of capacity, according to the FERC data.  New plant continues to exceed retirements.