Vehicle-to-grid (V2G) has massive potential to make transportation decarbonization more economically attractive while bolstering the broader power system. Here we discuss how traditional electricity retail rate design can render the business case of commercial fleet electrification in the United States less attractive by disincentivizing V2G participation. We tackle this issue bottom-up by introducing a high-resolution stochastic model to examine tariffs’ impacts on charging and frequency regulation bidding for a delivery fleet housed at a large warehouse. Using data from California for the rate design and frequency regulation prices, we show that absent a rate redesign, opportunities for both fleets and the grid are missed out. We propose a rate modification: demand charge relaxation during off-peak, overnight hours. This enables fleets to shift additional load share to overnight hours and substantially increase ancillary service revenues, with no impact expected on the local grid cost driver, i.e., the coincident peak load. Applying this change to a Pacific Gas and Electric tariff, we observe daily regulation capacity bids of ~5 MW and operational savings of 7.5% and 20.6% for a 20 EV and 60 EV fleets, respectively. Savings are driven by capacity revenues for smaller fleets and deferred demand charges for larger fleets.