This study evaluates the impact of a solar panel system installed on a heavy-duty truck (HDV) trailer on fuel consumption, tested at the ZalaZONE track. Two vehicles were assessed – diesel-powered and an liquefied natural gas (LNG) powered truck, with the latter equipped with solar panels. Over five days, the solar system powered cabin electronics, reducing idle time and fuel use. While fuel and carbon dioxide (CO₂) savings were observed, performance was limited by battery charge and sunlight exposure. The results show potential for up to 10% fuel savings, demonstrating the system’s feasibility for reducing emissions in long-haul transport, though further optimization is needed.