Last week, we detailed the explosion of U.S. wind development in 2012. As companies rushed to take advantage of the expiring production tax credit, the U.S. project pipeline was in overdrive. The wind industry installed more than 13 gigawatts of projects last year -- easily breaking the previous 2009 record of 10 gigawatts.

A lot of that development happened at the very end of the year. Take a look at the chart below from the U.S. Energy Information Administration. It shows that 40 percent of projects were finished in December as companies rushed to get their projects placed in service before the PTC expired.

In December, 59 wind projects came on-line, totaling 5,253 megawatts of capacity. According to EIA, that's the most capacity ever put on-line in one month in the U.S. wind market.

Congress eventually agreed to a last-minute extension of the PTC that applies to all projects starting construction in 2013. However, many analysts only expect 3 to 4 gigawatts of wind capacity to come on-line this year after companies put projects on hold due to uncertainty around the tax credit. If that's the case, U.S.solarinstallations could beat out wind for the first time this year.