This study aims to investigate the potential of biomass energy production under ground-mounted solar PV in Northern Thailand, by integrating the cultivation of dwarf Napier grass underneath the PV. The study was conducted in Northern Thailand, during November 2023–April 2024. Two systems were established within the 120 m2 investigated area: “System-I” for the open field area and “System-II” for the 8.6 kW ground-mounted PV area. Sunlight availability in terms of photosynthetic photon flux density (PPFD, μmol m‒2s‒1) was measured in both systems; then, recorded PPFD values were converted to daily light integral (DLI, mol m‒2d‒1). Dwarf Napier grass (NP) was planted in pots, and the pots were placed on both systems. Planting density was 4 plants per m2, with a spacing between plants 0.75 m. For data collection, 20 sampling plants of NP were selected (10 samples for each system) after 7 days of plantation. Fresh weight (FW, kg m‒2) was directly recorded after each harvest, and the plant samples were analyzed for proximate properties and higher heating value using the standard methods. The results showed that almost 80% of the NP in System-II received less sunlight than in System-I. The lower average FW values were found under System-I (0.68 kg m‒2) in comparison to System-II (1.48 kg m‒2). The average higher heating value from both systems was 15.95 MJ kg‒1. Then, the energy available in both systems was 10.82 MJ m‒2 in System-I and 129.60 MJ m‒2 in System-II (biomass = 23.52 MJ m‒2 and PV = 129.60 MJ m‒2). The results highlight the possibility of growing NP underneath PV and higher potential of energy production under System-II in comparison to System-I.