City officials in San Francisco, Calif. are considering a $19.5 million program that would give consumers the option of buying 100-percent renewable power at a higher cost. The so-called CleanPowerSF plan, which would be done in partnership with Shell Energy North America, would also invest about $2 million into the exploration of local green energy generation possibilities. If approved, city officials say, the program would slash carbon emissions during the first year by nearly 10 times the amount already achieved by the city’s green energy initiatives. According to the proposal, which is subject to a vote by the city’s Board of Supervisors, the program would increase utility bills for average customers by about $9 per month. About half of the city’s residents would automatically be enrolled in the program, but would have the chance to opt out at no charge within five months, city officials say. Neighboring Marin County has already initiated a similar program with Shell that allows customers the option of choosing renewable power.