74 electric school buses in Oakland have sent 1.7 GWh to the grid

On a typical school afternoon in Oakland, California, 74 electric buses are not on their routes at all. They are plugged into chargers, sending part of the power stored in their batteries back to the grid just as families get home and switch on air conditioning, the stove and the lights. Over the past two years, that small fleet has returned a total of 1.7 GWh of electricity to the grid, with 99.5% uptime.

The technique is called vehicle-to-grid, or V2G, which means a vehicle's battery can be used as storage for the power network. The idea has circulated for years, but it has rarely left the pilot stage. For a family car, the California Energy Commission estimates that home V2G could save a few hundred dollars per summer and cut peak demand by up to 5 GW statewide if it were widely adopted. The obstacle is that most homes would need costly equipment, and most electric cars are not yet V2G-enabled. Fleets avoid that problem. Instead of thousands of small installations scattered across a region, one depot concentrates many batteries in a single project that is easier to install and to aggregate.

The Oakland fleet works because the buses' daily rhythm fits the grid's. They charge overnight, use roughly 20 to 40% of their charge during the day, then plug back in after school. The fleet can discharge at about 2 MW at once. Electrek's estimate, based on an average evening use of about 2 kW per house, is that this is enough to power around a thousand homes, although peaks from heating, cooling and car charging can push that higher. The article describes the fleet as a small, reliable peaker plant, meaning a plant used mainly when demand is highest, and says it has delivered hundreds of thousands of dollars of electricity to the grid over the past couple of years.

For the public, and for cities, what changes is the timing and the cost of the power. Tellus says a depot can be deployed in months, where a conventional plant takes years to build and connect, and that its chargers avoid the large on-site transformers that slow other installations. For the Oakland school district, the logic is simple: buy power when it is cheap, sell it when it is expensive, and earn revenue from buses it already needs. The same model is being tested elsewhere: four school buses in Burlington, Vermont, two city bus chargers for Lynch Bus Lines in Burnaby, British Columbia, a pilot at three school district sites for ComEd in Illinois, and a San Francisco fleet of 104 buses scaling to 238. Tellus is also looking at electric garbage trucks, which follow similar daily schedules.

The limits are clear. These figures come from the reporting around the Oakland project and, for some of them, from the operator and the outlet's own estimates, rather than from an independent audit. The fleet's revenue depends on local electricity prices and grid services, which vary from place to place. Still, the project shows that a vehicle parked for most of the day can already be a dependable piece of the grid, with the next step being to make the same arrangement routine in more cities.