The San Francisco Clean Energy Act calls for the city to fulfill 51 percent of its energy needs through renewable energy by 2017, rising to 75 percent by 2030, and 100 percent "or the greatest amount technologically feasible or practicable" by 2040.
The controversial charter amendment would also require the city begin studies exploring the possibility of the city wresting control from private power companies.
Supervisor Ross Mirkarimi, the original sponsor of the charter amendment, said Tuesday it represents "what San Francisco's green energy should strive for."
Mirkarimi said it was "not a hostile takeover" of private power companies, but represented "what should be the indigenous right of San Franciscans."
Mirkarimi was joined earlier in the day by other supervisors, environmental advocates, and state Assemblyman and recently elected state Sen. Mark Leno, D-San Francisco, at a rally at City Hall in support of the measure.
"It's time for San Francisco to take control of its energy future," Leno said.
"We need to end our dependence on carbon-based fuels, and we need to do it now," Leno said. "The economics of energy are changing dramatically," he added.
Leno said public power represented "least cost, reliable service over maximizing profit."
The Board of Supervisors later approved introduction of the ballot measure by a 7-4 vote.