Electric vehicles (EVs) cannot utilize waste heat for cabin heating. Most EVs rely on PTC (Positive Temperature Coefficient) systems, which consume high energy and reduce driving range. This study proposes an air-source heat pump system for summer cooling and winter heating. Experiments evaluated its frosting and heating performance in low-temperature environments. Results show that lower ambient temperatures worsen frosting on the outdoor heat exchanger, reducing heating capacity; at −10 °C, the system fails to meet heating demands. Airflow velocity extremes (high or low) exacerbate frosting and degrade efficiency, while lower humidity mitigates frosting and improves performance. After 600 s of operation, the system’s COP drops below 1, indicating reduced energy efficiency. Integrating auxiliary heating is recommended to enhance overall performance in extreme cold conditions.