A report released today by the Solar Energy Industries Association (SEIA) claims that though the U.S. solar power sector was hard hit by policy changes and plunging global prices of photovoltaic (PV) panel prices, it installed 1,855 MW of PV capacity last year—more than doubling the previous annual record of 887 MW set in 2010.

The latest quarterly U.S. Solar Market Insight report from SEIA and GTM Research says that growth occurred in every market segment—residential, non-residential and utility—and in 18 of 23 states tracked individually. The dollar amount of project finance investments also reached an all-time high, and traditional energy companies such as MidAmerican Energy Holdings, Exelon, and NRG Energy became equity investors in the largest planned solar projects in the country, SEIA said.

The industry group noted that “not all developments in 2011,” were positive, however. The “highly valued” 1603 Treasury Program expired at the end of the year, which had the consequence of “complicating the financing of many new solar projects,” it said.

And though global PV module capacity grew more than 50% in 2011, “throughout most of the year global demand remained slow as a result of regulatory changes in Italy and tepid growth in Germany,” it said. In the second quarter of 2011, solar panel prices went into free-fall—plunging more than 50% during the year—and stabilized only in the last weeks of the year.

“This squeezed profit margins for every manufacturer, but it was particularly damaging for two types of companies: those that were less cost-competitive and those that were in the process of commercializing new technologies,” SEIA said. “As a result, multiple U.S. module manufacturing plants closed over the course of 2011.” But even so, U.S. module manufacturing capacity expanded 28%, the group said. Production remained flat for the year when compared to 2010.

2011 was the year in which SolarWorld and its six partners filed an anti-dumping/countervailing duty petition against Chinese crystalline silicon cell and module manufacturers with the Department of Commerce and the International Trade Commission, SEIA noted. “The outcome of the petition remains to be seen. However, it has already begun to impact procurement patterns and complicate the overall supply picture in the U.S.”

Meanwhile, last September, the controversy surrounding Solyndra, a solar thin-film module manufacturer, went national. “While Solyndra was never a significant player in the global solar industry, its default on a federal loan guarantee brought a high-profile political element that was absent for the other two U.S. solar bankruptcies in 2011 (Spectrawatt and Evergreen Solar),” SEIA said. “As a result, an industry blessed with overwhelming public support suddenly became a target for those who sought to admonish the loan guarantee program or clean energy policy in general.”

The report also provides an update on the concentrating solar power (CSP) market. Though no new concentrating solar thermal electric capacity was brought online in 2011, a total of 10 concentrating photovoltaic projects came online. The year also saw construction progress on a number of projects with some capacity expected to come online later in 2012 and much more in 2013. Today, more than 1,000 MW of CSP are under construction.

As of year-end 2011, cumulative PV capacity in the U.S. reached nearly 4,000 MW and cumulative CSP capacity topped 500 MW.