Board reviews vehicle-to-grid pilot for school bus battery, to consider tariff next month

The Concord Municipal Light Plant board reviewed a proposed vehicle-to-grid (V2G) pilot May 13 that would compensate a school district’s electric school bus and its third-party manager for energy supplied back to the utility.

Sustainability and utility staff explained the pilot is tied to a school grant and will be managed by a third-party operator responsible for charging strategy to ensure buses are ready for routes while offering grid services when possible. Laura described the technical scale: the expected school-bus battery system is roughly 66 kW — larger than a typical residential system but smaller than utility-scale batteries — and the grant requires third-party management of dispatch and data monitoring.

Tariff design: staff proposed billing deliveries to the bus under CMLP’s commercial EV charging rate (G4). For energy that the bus returns to CMLP, the proposal sets a flat energy credit (about 5.5¢/kWh) adjusted by an 85% cost factor to account for program administration and losses, plus capacity-style payments: a $14-per-kW monthly credit based on energy delivered during the monthly ISO regional coincident peak (totaling roughly $168/kW-year if the participant hit every monthly peak) and a $56-per-kW-year credit tied to the annual ISO coincident peak. Laura said the total value in the proposed tariff equates to about $224 per kW-year in the modeling staff shared and noted the figure is slightly less than comparable Mass Save residential program payments because CMLP must account for administration and losses.

Eligibility and scope: staff proposed the pilot target systems above 50 kW (meaning the school bus battery would qualify) and emphasized the pilot nature: the board would assess outcomes after a year of operation before considering wider application.

Board concerns and context: members welcomed a pilot but pressed on risk allocation — specifically whether the compensation structure places too much financial risk on the school or the third-party manager (battery degradation, the difficulty of predicting ISO peaks). Several members said the proposal’s emphasis on third-party dispatching and the short pilot term make the structure reasonable for an initial test. The board did not vote; staff will bring a formal tariff and pilot terms next month for board consideration and potential approval.

Why it matters: if successful, the pilot could show whether mobile batteries (school buses) can provide useful capacity and energy services to a municipal utility while helping to offset bus procurement or operating costs. Staff said the third-party manager and the grant framework are key risk mitigants for CMLP.