The midnight hour is fast approaching for the three major California utilities. According to state law, Pacific Gas & Electric (PG&E), Southern California Edison (SCE) and San Diego Gas & Electric (SDG&E) are by 2010 supposed to meet 20 percent of their retail electricity sales using renewable resources, like solar, wind and geothermal. It’s increasingly clear this ai’nt gonna happen.

It’s not as if the utilities have not made progress toward meeting California’s renewable portfolio standard, which is among the country’s most ambitious. Officials from each utility have signed power purchasing agreements (PPAs) up and down the state, but they’ve faced a range of challenges. Financing, for instance, has sometimes been difficult to come by. The same may be said of land-use permits.

With six months to go, the California Public Utilities Commission (CPUC) says the utilities will likely push their way up to 18 percent by the end of the calendar year — two percent short of the goal.

Despite a flurry of activity, it’s plausible PG&E, SCE and SDG&E may come up shorter still. Executive Director of the Center for Resource Solutions in San Francisco, Arthur O’Donnell, suggests that not all the projects that have been planned on paper will translate to viable projects in reality. Some observers argue a portion are not feasible, and were only advanced by the utilities in an effort to meet the deadline.

According to the Los Angeles Times, full accounting of the utilities renewable energy capacity won’t come into effect until 2013. The 2010 mandate contains a flexible-compliance provision that gives the utilites three more years to meet the goal before penalties are enforced. Critics are pointing to this provision as the reason why the utilities have not been more selective in signing contracts with power producers.

The utilities, for their part, point to other factors that may have impeded progress. SDG&E is blaming the low number on the lack of renewable energy resources in its immediate service area. In the case of SCE, the development of critical transmission infrastructure has been slow: only three of 11 segments planned for the utility’s $2.1 billion Tehachapi Renewable Transmission Project have been completed.

Regardless of the exact causes, the recent experience of California is a testament to the kinds of challenges that arise when states initiate the transition toward a clean-energy future.