At this evening’s 7 o’clock City Council meeting in Council Chambers, members will be asked their position on an energy efficiency bill by two of the state Senate’s most liberal Democrats, Kevin de Leon and Mark Leno.

While Mayor Mehaul O’Leary is due back on this day from his native Ireland, if he is not, Vice Mayor Andy Weissman will affix his signature to a document of support or opposition.

Senate Bill 350, linked to climate change, is markedly inspecific, as Mr. Weissman noted this morning.

SB 350’s authors maintain that by reducing petroleum use, what they call “fossil fuels,” and by vaguely increasing “energy efficiency,” jobs will be created and California’s tottering economy will be strengthened. Sens. Leno and de Leon do not say exactly how they can make that happen.

Here are their two main contentions:

“According to the California Air Resources Board, production, refining, and the use of petroleum accounts for nearly half of greenhouse gas emissions, 80 percent of smog-forming pollution, and over 95 percent of cancer-causing diesel particulate matter. The Air Resources Board notes that oil dependence costs the state $33-$55 billion annually, and that reducing petroleum use and improving vehicle efficiency will cut costs and improve California’s economic productivity and competitiveness.”

Their second point:

“Energy efficient buildings save money and reduce pollution from electricity. According to the California Energy Commission, efficiency standards return an average of $6,200 in energy savings per household over 30 years, or $27 per month on heating, cooling, and lighting bills. These same standards save 200 million gallons of water per year (equal to more than 6.5 million wash loads) and avoid 170,500 tons of greenhouse gas emissions per year. Since 1978, the state’s standards have saved Californians $66 billion in electricity and natural gas savings.”

Mr. Weissman said that while SB 350 is labeled an environmental measure, “I am troubled by the fact it is unclear. The staff report for tonight says there will be significant changes if the legislation is adopted. The changes aren’t detailed. I would like clarification.

“I believe we don’t know what the full extent of the legislation would be, what its impacts would be, and what its costs would be,” Mr. Weissman said.