alarm clockTime’s up.Photo: elfonThe California Legislature is moving to put into law a regulation requiring the state’s utilities to obtain a third of their electricity from renewable energy by 2020. But how did California’s three big investor-owned utilities do in meeting a previous mandate to secure 20 percent of their electricity supplies from carbon-free sources by the end of 2010?

Close, but not quite. Overall, the three utilities — Pacific Gas & Electric, Southern California Edison, and San Diego Gas & Electric — are getting 18 percent of their electricity from wind farms, solar power plants, geothermal, and biomass facilities, according to a new report from the California Public Utilities Commission.

Southern California Edison fell just short with 19.4 percent of its power coming from renewable sources. PG&E didn’t do as well but 17.7 percent of its electricity is green. The smallest utility, San Diego Gas & Electric, is the brownest of the bunch, with renewables accounting for only 11.9 percent of its power portfolio.

State regulators estimate that the three utilities will collectively hit the 20 percent target — one of the most aggressive in the United States — by the end of 2012. Of course, they have an even bigger mandate to meet eight years after that.

The good news is that the trajectory looks positive, if the growth in renewable energy generation in recent years is any guide. For instance, the percentage of green electricity in PG&E’s portfolio jumped from 14.4 in 2009 to 17.7 in 2010 while Southern California Edison increased its percentage of renewable energy by two points in 2010.

Hitting the so-called RPS — renewable portfolio standard — admittedly is a tricky business. A review of more than 200 renewable energy projects the utilities have signed shows that many have come online, some have cratered, and others are in limbo as environmentalist and developers face off over the impact of big solar power plants on desert flora and fauna.

There have also been big changes in renewable energy technology in recent years. The price of photovoltaic modules has plummeted over the past two years and utilities have been recently signing deals to buy electricity from photovoltaic farms at a pell-mell pace.

Still, expect stricter scrutiny of these deals as the 2020 deadline approaches, pressure mounts to make good on the 2010 mandate, and Gov. Jerry Brown’s new appointees to the public utilities commission weigh in.

Of the hundreds of renewable energy contacts the utilities have submitted for approval, only two have been rejected — a wave energy deal and a wind project.

Meanwhile, regulators list a project to transmit 200 megawatts of electricity to PG&E from an orbiting space-based solar farm as “on schedule.”

Beam me down, Scotty.