With the advent of the electric vehicle (EV) revolution, the market share of EVs has been steadily increasing, accompanied by growing interest in the heat pump air-conditioning system (including cooling and heating functionalities) of electric vehicles. As the second-largest energy-consuming system in a vehicle, the air-conditioning system significantly impacts driving range, especially under winter heating conditions, where excessive energy consumption can greatly reduce the vehicle’s range. This study addresses the issue of high energy consumption of heat pump air-conditioning systems in winter. By constructing a one-dimensional model of the heat pump air-conditioning system for electric vehicles, the study analyzes the impact of compressor speed, EHX opening, and recirculation ratio on energy consumption and heating capacity under WLTC operating conditions at an ambient temperature of −5 °C. The results indicate that an EHX opening of 450 steps, an external air circulation ratio of 30%, and a compressor speed of approximately 5000 RPM provide optimal heating performance for the heat pump air-conditioning system. This simulation offers insights for optimizing heat pump air-conditioning systems and improving the driving range of electric vehicles. Further optimization could enhance EV range issues and boost the market competitiveness of this type of electric vehicle.