Peter Darbee is trying to build the country's greenest utility.

As head of PG&E Corp. in San Francisco, Darbee has spent much of his tenure trying to convince fellow business executives that global warming is a threat. He has thrown the company's weight behind state laws designed to fight climate change. He has become a frequent visitor to Capitol Hill, where he pushes for a nationwide system to limit the greenhouse gas emissions blamed for heating the planet.

He also has tried to make green part of PG&E's public image. Ads for Pacific Gas and Electric Co. tout the company's use of solar power, windmills and hydroelectric dams. But at the same time, PG&E is scrambling to find enough renewable energy to satisfy state requirements.

Darbee recently talked with The Chronicle's business staff about climate change, renewable power, utility bills and a San Francisco government proposal to buy electricity for the city's citizens, replacing PG&E. The following has been edited for space and clarity.