Vehicular networks offer service coverage for urban environments that would otherwise be too expensive for infrastructure-based networks to provide. While many services have already been proposed based on collaboration between moving cars, the inclusion of parked cars in these systems extends their reach, coverage and stability. However, despite the presence of a large car battery, cars still suffer from limited energy availability when they are parked. Essentially, if there is not enough energy to power the system for the whole duration of the stop, energy must be saved by shutting down the services for part of the stop duration. In this paper, we propose an energy management framework that governs the energy provisioning of a service. Our governor guarantees the most effective energy utilization for the system, requiring minimum effort from the service designers to attach to the system. We demonstrate the effectiveness of our governor through simulation of our LoadingZones Internet connectivity service and the feasibility of the architecture through the evaluation of our prototype system.