Perhaps it reflects a very American belief in the competence of private industry versus the government, but in the United States the most credible and widely referenced source for solar installation data is not a government agency. Instead, it is the reports put out quarterly by GTM Research and Solar Energy Industries Association (SEIA).
Today these organizations released fourth quarter and full year estimates for U.S. solar installations, finding that the market grew 17% to 7.3 GW in 2015. And while utility-scale solar still represented the majority of the market at over 4 GW the residential sector grew 66% annually, with over 2 GW installed during the year.
Solar passed another tipping point; for the first time more solar than natural gas-fired generation was installed in 2015, with solar representing 29.5 of new electric generating capacity during the year.
California remains the largest market, but 13 states installed more than 100 MW of solar over the course of the year. The U.S. solar market remains concentrated in key states, with the top ten states accounting for 87% of installed capacity in 2015, noted GTM Research Senior VP of Research Shayle Kann. But growth has been widespread, and 24 of the 35 states that we track individually saw market growth in 2015."
There are clouds on the horizon for several of the leading state markets. During 2015 Nevada remained the 3rd largest market, however the states fast-growing residential segment has been stopped in its tracks by state regulators, who have imposed the most regressive changes to net metering seen in any state to date.
The #2 and #4 largest markets are also in trouble. A key tax incentive effectively expired for solar at the end of 2015 in North Carolina, the second largest market, and 4th-place Massachusetts is beginning to hit caps on net metering which will halt the states mid- to large-commercial and community solar markets.
Despite these difficulties, the U.S. market is poised for larger growth this year, as a number of utility-scale projects planned before the extension of the federal Investment Tax Credit (ITC) come online.