The United States experienced record growth in solar installations, an industry report says.

A total of 3,313 megawatts of capacity was added in the United States last year, bringing the national solar photovoltaics total to 7,221 megawatts. That's a 76 percent increase compared with 2011, says the report released Thursday by the Solar Energy Industries Association and GTM Research.

"We've brought more new solar online in 2012 than in the three prior years combined," SEIA Chief Executive Officer Rhone Resch said in a statement.

"There were 16 million solar panels installed in the U.S. last year -- more than two panels per second of the work day -- and every one of these panels was bolted down by a member of the U.S. workforce," he said.

The report forecasts 4,300 megawatts of new PV installations for 2013, an increase of 29 percent over 2012.

Resch credited supportive government policies for helping to spur the growth and called for longer-term policies to provide certainty to the solar sector.

"You need the same certainty that has been provided to the oil, natural gas, coal and nuclear industries," he said in releasing the study results.

SEIA says the market value of solar installations reached $11.5 billion in 2012, from $3.6 billion in 2009.

"Amidst this boom, the industry faced newly imposed import tariffs on Chinese solar cells and ongoing consolidation in the manufacturing space," said Shayle Kann, vice president at GTM Research.

Last year, the U.S. International Trade Commission imposed a 36 percent tariff on Chinese solar cell manufacturers, for dumping cheap products on the U.S. market.

John Smirnow, vice president, Trade and Competitiveness for SEIA told PV Magazine, "The tariffs did have [the desired] effect of barring Chinese cells from entering the U.S. market."

Average costs for residential systems dropped nearly 20 percent in one year, from $6.16 per watt in 2011 to $5.04 per watt in 2012.

California led the nation in the number of megawatts installed, says the SEIA report.

An update Thursday from the California Public Utilities Commission indicated that the state has installed 1.5 gigawatts of rooftop solar. That's almost equal to the amount of power generated by three medium-sized coal-fired power plants, says environmental group Environment California.

Under its "Million Solar Roofs" program created in 2006, California, with the help of $3.3 billion in incentives, aims to generate 3 gigawatts of solar power by 2016. The state had passed the 1 gigawatt benchmark in November 2011.