Vehicle-to-building (V2B) systems combine physical infrastructure such as smart buildings and electric vehicles (EVs) connected to chargers at the building, with digital control mechanisms to manage energy use. By utilizing EVs as flexible energy reservoirs, buildings can dynamically charge and discharge EVs to effectively manage energy usage, and reduce costs under time-variable pricing and demand charge policies. This setup leads to the V2B optimization problem, where buildings coordinate EV charging and discharging to minimize total electricity costs while meeting users’ charging requirements. However, the V2B optimization problem is difficult due to: 1) fluctuating electricity pricing, which includes both energy charges ($/kWh) and demand charges ($/kW); 2) long planning horizons (usually over 30 days); 3) heterogeneous chargers with differing charging rates, controllability, and directionality (unidirectional or bidirectional); and 4) user-specific battery levels at departure to ensure user requirements are met. While existing approaches often model this setting as a single-shot combinatorial optimization problem, we highlight critical limitations in prior work and instead model the V2B optimization problem as a Markov decision process, i.e., a stochastic control process. Solving the resulting MDP is challenging due to the large state and action spaces. To address the challenges of the large state space, we leverage online search, and we counter the action space by using domain-specific heuristics to prune unpromising actions. We validate our approach in collaboration with an EV manufacturer and a smart building operator in California, United States, showing that the proposed framework significantly outperforms state-of-the-art methods.