San Francisco Mayor Mark Farrell and the San Francisco Municipal Transportation Agency (SFMTA), which operates MUNI (the city’s public transit), announced San Francisco’s commitment to have an all-electric bus fleet by 2035. SFMTA will only purchase all-electric buses starting in 2025 to meet the goal for 2035.

The SFMTA Board of Directors on Tuesday approved a resolution supporting the commitment towards an all-electric bus fleet along with a pilot program to evaluate and implement battery electric vehicles. MUNI currently operates the largest fleet of electric trolley buses.

The trolley buses, like all light rail, streetcar, and cable car vehicles in the city, run on Hetch Hetchy hydroelectricity via overhead wires. MUNI also runs a fleet of hybrid electric vehicles which use renewable diesel.

One of MUNI’s newer 40' electric trolley buses.

(The Hetch Hetchy watershed, an area located in Yosemite National Park, provides approximately 85% of San Francisco’s total water needs. Owned and operated by the San Francisco Public Utilities Commission, the Hetch Hetchy system also has a combined total hydroelectric generating capacity of approximately 385 megawatts. Hydroelectricity from Hetch Hetchy powers all of the City’s municipal facilities (SFO, SFGH, MUNI, fire stations and more), residents and businesses in the Hunter’s Point Shipyard, Treasure Island and other retail customers. )

We are excited about the possibility that by 2035 we will be able to provide an all-electric fleet that won’t require overhead wires.

—Cheryl Brinkman, Chairman of the SFMTA Board of Directors

The SFMTA has been rolling out new electric hybrid buses with higher capacity on-board battery systems. The increased on-board battery capacity will allow the SFMTA to run a test program to operate “Green Zones” along several electric hybrid routes that would run only by battery for significant portions of the route. The “Green Zone” signifies an area in which the vehicle will not produce any emissions. The SFMTA is working to identify these zones throughout the city.

The SFMTA said it will move forward with electric bus technology when manufacturers can prove their electric buses can withstand heavy ridership and the steep hills characteristic of San Francisco. The agency would also have to consider new facilities that can charge a large fleet and developing a systemwide infrastructure to charge vehicles in service or on the street.

While the battery technology is emerging rapidly, it isn’t quite ready for primetime. Manufacturers aren’t yet producing the number of all-electric buses San Francisco and other urban areas would need, nor could we guarantee that the vehicles would work for the required 15 years with heavy ridership and challenging topography.

—John Haley, SFMTA’s Transit Director

In 2019, the SFMTA intends to purchase a limited number of battery electric buses and test them in service throughout San Francisco to evaluate how they perform on crowded and hilly routes. SFMTA said that the most important step to support the zero-emission goal is to determine the infrastructure needs for electric buses, including upgrades for existing facilities to accommodate charging requirements and maintenance.

Of the nearly 900 all-electric buses purchased across the country, only 207 are actually in service, SFMTA said. By contrast, MUNI is currently operating 250 electric trolley vehicles.

In recent years, the SFMTA has replaced more than 90% of its older diesel buses with cleaner, more efficient electric hybrid vehicles that run on renewable diesel. These electric hybrid vehicles offer lower fuel consumption, decreased engine idling time while in service, and a substantial reduction in emissions. The SFMTA’s switch from conventional diesel to electric hybrid vehicles has reduced consumption of fuel by 5.4 million gallons and 82,000 tons of CO₂ over the 12-year life of the fleet.

San Francisco’s transportation sector generates approximately 46% of the City’s total greenhouse gas emissions, mostly generated by the use of private cars and commercial trucks. MUNI carries 26% of all trips in the city, but accounts for less than two percent of these emissions.

On 19 April 2018, Mayor Mark Farrell committed San Francisco to net-zero greenhouse gas emission by 2050.