Recent advances in the electromobility of bus fleets improve transit service sustainability but require the development of vehicle recharging facilities. The paper defines a methodology to design an efficient transit network operated by battery electric buses in cities with grid-shaped road network, based on continuous approximations. An analytical model defines the optimal network configuration that minimizes the agency cost, the monetization of emissions and the travel time of transit users. The analytical model allows the comparison of total cost, emissions and bus performance to other fuel powertrains. The methodology is tested in Guadalajara (Mexico) to propose an alternative bus configuration, outperforming the current bus service and reducing the agency cost and environmental impact. The analytical model justifies the network rationalization in fewer routes to reduce the total cost of the system. The deployment of standard battery electric buses with opportunity charging scheme obtains the lowest total cost of the system.