2013 has been an impressive year for solar power.

In the past 12 months, California more than doubled its entire rooftop solar installations from 1,000 MW to over 2,000 MW.

To put this in perspective, it took California over 30 years to build 1,000 MW of rooftop solar, hitting that landmark in early 2013. Today, California is closing out the year with more than 2,000 MW of rooftop solar systems installed statewide. The California Public Utilities Commission's (CPUC) latest figures report 1,917 MW of rooftop solar, but those numbers exclude basically all of Pacific Gas and Electric's 2013 installations, by far the largest market in the state, as well as a significant number of installations in other utility territories.

By comparison, California added 500 MW of distributed solar in 2012 – also a banner year. If California continues to grow its rooftop solar market at its 2013 pace, the state may very well top 5,000 MW in 2014 – far exceeding the goals of the Million Solar Roofs Initiative, which aimed to install 3,000 MW of rooftop solar by the end of 2016.

When utility-scale solar projects are added in, California's total solar power picture well-exceeds 4,000 MW today – nearly twice as much installed capacity as exists at California's last remaining nuclear power plant, Diablo Canyon.

These numbers aside, California won't have a clear picture of 2013 – or 2014 for that matter – until all of the utilities' data on rooftop solar installations is released to the public – something resisted by the utilities and still pending at the CPUC.Â

Meanwhile, rooftop solar continues to face battles on multiple fronts with regards to net metering, incentives for solar heating and cooling systems, the future of tax credits, and the reining in of permitting and interconnection costs and obstacles. Whether California continues this historic growth depends largely on policy decisions to be made in 2014.

As reports of 2013 being the driest year in California history roll in, California's solar power growth is long overdue by many accounts. But no matter how you slice and dice the numbers, 2013 was a good year for solar power and another example of California's leading the country toward a clean energy future.

Bernadette Del Chiaro is executive director of the California Solar Energy Industries Association.