In 2014, Chicago purchased two fully electric buses, becoming one of the first major U.S. cities to do so. The Chicago Transit Authority reports that the agency saves $25,000 on fuel and it calculates that the cleaner air saves $55,000 on the “avoided healthcare impacts” per bus per year.

In a 2017 report, King County Metro calculated their annual operation cost savings at a more modest $10,000 per bus. Metro Spokesperson Jeff Switzer says their fully electric buses have not been in operation long enough to get a definitive financial picture, but, “operating cost savings look increasingly promising. They’re greater than what we published in our 2017 zero-emission feasibility report.”

Speight says one of the best benefits of electric buses is that they don’t run on diesel. Diesel soot is laden with toxic chemicals including “known or suspected carcinogens such as benzene, arsenic and formaldehyde.” Buses running on fossil fuels also contribute to climate change. In Washington state, the transportation sector accounts for around 43 percent of Greenhouse Gas emissions.

Still, it is not surprising that there are so few electric buses operating in the U.S. The technology has only come online in the last several years and public agencies tend to loath unproven experimenting. There’s also the fact that the typical lifecycle of a transit bus is 12 years. If a bus was purchased just before battery electric buses started becoming available, it might have as many as eight or nine years left on the road.

Metro’s Switzer says there are a few hurdles to overcome as they try to move to an entirely battery electric bus fleet. The first is the ability of the equipment they need. He says Metro has the largest fleet of 60-foot articulated buses (they’re the long buses with the accordion center section) in the country. The U.S. only got its first electric 60-foot articulated bus in May 2017.

Switzer says there are also still issues around standardizing bus-charging infrastructure and questions of how best to add charging stations to the agency’s existing bus bases.

Metro is still well ahead of Sound Transit on its electric bus efforts. Sound Transit spokesperson Rachelle Cunningham says that the agency is still in the feasibility stage of electric bus adoption. Last year, they did a “cost-benefit analysis and high-level feasibility study to evaluate battery electric bus technology.” In the coming years, she says they plan to do a more comprehensive analysis for their ST Express system of buses.

The agency has a goal of making their buses carbon neutral by 2050 and expects electric buses to be “part of that equation.” But for now, Cunningham says, “Some of our current limitations include the fact that we are about halfway through the expected lifespan of our bus fleet, and our business model, which relies on our partner agencies operating and maintaining our buses, limits what we can do in terms of propulsion shifts.”

Speight is sympathetic that public agencies have to factor in bus lifecycles and cost into their decision making. But, he thinks the case against shifting is getting thinner. For one, there’s money on the table to buy electric buses and charging stations with. As part of the Volkswagen scandal settlement, which involved the automaker’s deliberate understating of its diesel emissions, Washington state got more than $112 million and plans to spend about 45 percent of it on electrification of trucks and buses.

“This is an investment that’s going to have immediate public health and environmental benefits in communities in Washington,” Speight says. “You have to eventually replace buses anyhow. As agencies replace their fleets they must invest in electric.”

Correction: An earlier version of this article misidentified Metro’s electric trolley buses as diesel-electric hybrids.