The routing of an electric vehicle often requires planning stops at charging stations to recharge the vehicle’s battery. At the same time, the price of electricity, the charging technology, and the waiting time at a charging station (CS) can impact routing and charging decisions for a fleet of vehicles. We introduce the Electric Vehicle Routing Problem with Heterogeneous Charging Stations (E-VRP-HC). We simultaneously consider charging functions (which are nonlinear in nature), time-dependent waiting functions, and time-of-use electricity pricing at CSs. The advantage of considering this function explicitly is that we can reduce costs by avoiding peak queuing times at CSs or periods with high charging prices. The objective function is to minimize the sum of the route duration costs, charging costs, and vehicle fixed costs. To solve this problem, we propose a path-based mixed-integer linear programming formulation, which does not require time discretization to track charging costs. The formulation can be solved using a general-purpose solver to find optimal solutions for small-sized instances. However, tackling this large-scale problem is challenging given the fact that determining an optimal vehicle’s time schedule for a given route in this context is already a complex optimization problem. To address this, we propose two methods for the time scheduling problem: (i) an exact method that obtains an optimal schedule but is computationally intensive and (ii) a heuristic method that can provide a high-quality solution in a very short time. Building upon these two optimization subroutines, we develop an effective metaheuristic framework to solve large-scale instances. The proposed model and heuristic are validated on two sets of benchmark instances: a newly designed benchmark set, and a real-world dataset from Beijing. The computational results on benchmark instances demonstrate the performance of our approach in handling the complexity of the E-VRP-HC. Numerical tests on the real-world dataset show that considering the time-of-use pricing function and nonlinear charging function can significantly reduce costs. Finally, we provide valuable managerial insights based on the results of our computational experiments.
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