By Todd Woody | Bloomberg
In an industrial corner of Oakland, wedged between a 10-lane freeway and a freight terminal, sits California’s newest source of renewable energy: a squadron of shiny yellow electric school buses. It’s the first all-electric bus fleet serving a major US school district. Starting in August, the 74 vehicles will also supply 2.1 gigawatt-hours of electricity to the Bay Area power grid, enough energy for 300 to 400 homes.
The buses are expected to reduce carbon dioxide emissions by about 25,000 tons annually in a city where 72% of public school students come from low-income families, who are disproportionately impacted by pollution from Oakland’s busy port, truck traffic and manufacturing facilities. Alameda County, where Oakland is located, has some of the nation’s worst air pollution, according to an American Lung Association report released this month.
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The Oakland Unified School District’s previous diesel bus fleet gave children no respite from pollutants linked to lung diseases like asthma. “I would wipe my fingers along the inside of the bus at the end of the day and they would be black from diesel smoke,” says Marjorie Urbina, who has been driving school buses for 23 years. “If it’s in the bus, it’s in my lungs.”
Most of the 480,000 school buses in the US run on diesel fuel, and low-income students account for 60% of the 20 million children they transport daily, according to the World Resources Institute. Heavy-duty trucks, a category that includes school buses, comprise just 6% of vehicles in the US but emit 59% of pollution from road transportation.
“School bus electrification can really play an important role in making our air healthier for everyone, especially children,” Harold Wimmer, chief executive officer of the American Lung Association, said Wednesday during a webinar on electric school buses.
Oakland’s electric buses are provided by Zūm, a Silicon Valley startup that now manages the school district’s fleet, as well as those in Chicago, Dallas, Los Angeles, Seattle and other US cities. Zūm began to add electric buses to its fleet in 2022 and about 10% of the company’s 3,000 buses are now zero-emission. As Zūm converts more of its fleet to battery power, Oakland offers lessons for other districts on how to ditch diesel and help pay for electrification by using buses to provide power to the grid.
“Electric school buses are a unique fleet as they’re essentially large batteries on wheels that drive very few, predictable miles and can support the grid,” says Vivek Garg, Zūm’s co-founder and chief operating officer, standing in the OUSD depot next to a row of buses manufactured in Southern California by Chinese EV giant BYD.
School bus schedules align nicely with renewable energy production and electricity demand, making them ideal for vehicle-to-grid programs.
When the new school year begins in August, Urbina and other Zūm drivers will leave the depot in the morning with 110 miles of range at the ready to pick up students from their homes and take them to school. The drivers will return to the depot at around 10:30 a.m. with batteries at 68% capacity. Solar energy production in California ramps up at that time, so drivers will plug the buses into bidirectional chargers designed by Zūm, taking advantage of lower electricity rates.
Their batteries topped off, the buses head out again around 1:30 p.m. to shuttle students home from school. They’re back in the bus yard by 5:30 p.m. as renewable energy production falls off with the setting sun and electricity demand and rates start to peak. The buses plug back into the chargers — except now they’re sending green electricity to the grid at a time of day when utilities typically rely on fossil fuel power plants. When demand and rates fall after 9 p.m., the buses begin charging so they’re ready to roll the next morning.
“There is an excess of supply during the solar peak and this is a way we can move some of that energy from that time of the day to when we actually need it,” says Rudi Halbright, product manager for vehicle-grid-integration pilots and analysis at California utility Pacific Gas and Electric Company. “With 74 buses, that’s a lot of power so it really has a big impact for us. This pilot specifically is designed to pave the way for us to do this on a large scale.”
When Kim Raney, OUSD’s executive director of transportation, negotiated a contract with Zūm in 2019 to provide and manage bus transportation, she insisted the fleet transition to electric by August 2025. The district only offers busing for special education students, who account for 17% to 20% of its school population. “These students already suffer from learning disabilities and they had to spend an hour a day on a noisy, stinky bus,” Raney says. “Half our kids don’t even see electric cars, let alone get to ride in one. So this is going to be a game changer for these families.”
Legislation enacted last year requires all newly purchased California school buses to be zero-emission beginning in 2035. Electrifying school bus fleets, though, is a challenge for cash-strapped school districts. Even the smaller, 26-seat electric buses being deployed in Oakland can cost $350,000, triple the price of a same-size diesel vehicle.
To make the math work, Zūm’s electric buses were subsidized by grants from the US Environmental Protection Agency’s Clean School Bus Program, as well as money from the state and the regional air quality district. Raney and Garg say PG&E was key to the financial viability of the project. The utility paid for transmission upgrades needed to supply 2.7 megawatts of power to the bus chargers and it will also compensate Zūm for the electricity the buses return to the grid.
California’s 2023 school bus law also extends the maximum term of a contract for zero-emission buses between a school district and a private operator to 15 years from five. Garg says the guarantee of such long-term contracts will make it easier to obtain financing for electric buses.
Zūm’s technology also helps cut the cost of electrification. An app increases the efficiency of the fleet by giving drivers a list of students to be picked up each day and plotting the routes. If a student won’t be in school that day, the app reroutes the bus. And given the vehicles’ predictable energy demands, they can be charged at a lower voltage, avoiding installation of expensive fast chargers.
At the OUSD depot, Urbina boards an electric school bus for a short drive around the yard. The bus is air-conditioned so the windows can remain closed, further reducing children’s exposure to air pollution. An even starker contrast to the ear-splitting din of diesel buses: It’s silent.
“I love that it’s quiet,” Urbina says, “because when the bus is loud, kids get louder.”
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