SAN FRANCISCO — A group of San Francisco Bay Area cities, counties and water agencies has joined forces for what is being billed as one of the largest single government purchases of all-electric vehicles in the country.

The six cities, two counties and two water agencies have gone in together to buy 90 electric vehicles with the help of a $2.8 million grant from the Metropolitan Transportation Commission, a regional transportation agency, officials with the Bay Area Climate Collaborative said on Tuesday. Some of the vehicles will be on display at a news conference on Tuesday.

The vehicles will save more than $500,000 in fuel costs and about 2 million pounds of carbon dioxide emissions over five years, Bay Area Climate Collaborative Executive Director Rafael Reyes said.

The collaborative — a public-private partnership started by three Bay Area mayors — developed the proposal for funding that was submitted to the Metropolitan Transportation Commission.

The Bay Area is clearly in a leadership role here, Reyes said.

The vehicles include the Ford Focus and the Nissan Leaf. The total cost was $5 million, with the rest of the money coming from funds set aside by the governments and agencies to buy new vehicles.

The 10 governments and agencies are: San Francisco, San Jose, Oakland, Santa Rosa, Fremont, Concord, the Sonoma County Water Agency, Marin Municipal Water District, and Alameda and Sonoma counties.

San Jose and three other Bay Area cities bought 50 all-electric vehicles last year, Reyes said.

The all-electric vehicles are a small part of the cities, counties and water agencies overall fleets. But Reyes said the purchases shows what can be done.

Were just scratching the surface, he said.