According to the SNL Energy report, new generating capacity added to the aging US fleet in 2014, at 15,450 MW; this was slightly more than the 15,028 MW added the year before.

Looking at 2014's new capacity by fuel type, slightly more than half, or 7,902 MW, was gas-fired. Almost 92% of the new gas-fired capacity coming online was at combined-cycle facilities. A number of new gas plants were built as replacements to older, usually coal-fired units that were retired.

In terms of renewables, wind accounted for the second-largest amount of capacity added, almost 3,815 MW during the year. As wind developers rushed to capitalize on the brief extension of production tax credit, the month of December saw almost one-third of all of 2014's wind capacity additions. According to the American Wind Energy Association, the levelized cost of energy from wind sources has declined 58% over the past five years; this, combined with increasing capacity factors, has been the most significant factor driving increased wind installations.

With respect to solar, new capacity totaled 3,240 MW in 2014. Experts say solar installations likewise benefited from decreasing system costs in 2014. According to data from the Solar Energy Industries Association, the national weighted-average system cost for residential and utility-scale solar facilities declined nearly 4%.

The full report from SNL Energy, which includes corresponding charts and tables, is available online.