Centralized vehicle-to-grid coordination for behind-the-meter value in commercial fleets: Evidence and deployment lessons from a pilot demonstration

Vehicle-to-grid operation in commercial fleets remains debated due to interoperability limits, user acceptance, warranty concerns, and regulatory uncertainty. This paper reports a five-week multi-site pilot demonstration in mainland Portugal evaluating a centralized coordination architecture that uses V2G and low-complexity rule-based control to capture behind-the-meter value: energy arbitrage under time-of-use tariffs, peak-load shaving, and photovoltaic surplus self-consumption, relying only on site telemetry, charging-session data, and conservative state-of-charge (SoC) limits agreed with fleet users. Across three sites, 374 kWh of charging was shifted from peak to off-peak periods, 150 kWh was discharged during peak periods, and 16.6 kWh of additional charging was enabled from solar surplus. These actions resulted in €20 of EV charging cost savings (a 26% cost-weighted reduction against the rebased baseline), €7.9 of site-level energy savings, and an estimated €39.4 reduction in demand-related charges, modest and highly site-specific values. Average departure SoC decreased from 96% to 79% but remained above the agreed 50% minimum throughout the pilot. Beyond these outcomes, the study draws deployment lessons on measurement uncertainty, control-interval limits, plug-in behavior, battery-condition observability, protocol maturity, deployment cost, and regulatory constraints.