• Monitoring 200 PV-equipped trucks in real business. • 30% of overpromises, but was explained by shading impacts. • Fuel-saving was estimated 7% but varied among trucks. This study examines the real-world performance and potential for fuel savings of Vehicle-Integrated Photovoltaics (VIPV) installed on heavy-duty vehicles (HDVs). A comprehensive nationwide monitoring campaign was conducted involving approximately 200 commercial trucks equipped with 300–500 W CIGS photovoltaic systems. Data collected included photovoltaic output, alternator behavior, battery flow, and vehicle operation. Unlike prior VIPV investigations, this research provides the first extensive, long-term dataset obtained under actual commercial logistics conditions, facilitating a quantitative assessment of alternator suppression and fuel-saving effects across various truck types and driving environments. To accurately estimate solar irradiance under fluctuating shading conditions, the study employs a validated local-coordinate irradiance model and utilizes statistical methods to determine nominal PV generation. Results indicate that actual VIPV performance approximates 70% of the theoretical irradiation ratio predicted by standard models, primarily due to shading, orientation variations, and alternator control dynamics. Across all monitored vehicles, VIPV reduced alternator load by an average of 102 W during operation, corresponding to an estimated fuel consumption reduction of approximately 7%, with variations depending on truck type and driving pattern. Extrapolating these findings to Japan’s HDV fleet suggests that widespread VIPV implementation—coupled with anticipated technological advancements that increase fuel-saving efficiency to 12%—could reduce greenhouse gas emissions by roughly 4% of the transport sector’s total emissions. These findings demonstrate that VIPV is a practical and scalable approach to decarbonizing logistics operations, supported by empirical evidence from real-world operational data.
Araki et al. (2026) studied this question.