Taiwan faces challenges in expanding solar energy due to limited land availability. Offshore floating photovoltaic (OFPV) systems have emerged as a promising alternative, supported by recent deployments in retention ponds, reservoirs, and coastal areas. Using the Product Carbon Footprint Category Rules (CFP-PCR) framework, this study conducts a comparative carbon footprint inventory analysis of a 100 MWp onshore photovoltaic (LPV) system and a 181 MWp intertidal OFPV project in Changhua, Taiwan’s first large-scale commercial OFPV installation, based on a life-cycle energy assessment approach. To ensure methodological consistency, unified assumptions are applied to both systems, including the same photovoltaic module type, the same project lifetime (25 years), the same degradation rate (0.5% annually), and the same functional unit (100 MWp). Manufacturing emissions are derived from CFP-PCR-aligned datasets that reflect Taiwan’s import-dependent photovoltaic supply chain, while avoided operational emissions are calculated using Taiwan’s official grid emission factor.

Under these assumptions, the OFPV system produces approximately 2,047.1 GWh over its lifetime, compared to 1,827.8 GWh for the LPV system, representing an increase of about 12%. This corresponds to an estimated CO2 reduction of 1.013 Mt for OFPV, compared to 0.905 Mt for LPV, and a projected benefit of approximately 12% more under emissions trading mechanisms. The specific environmental characteristics of the intertidal installation—including periodic exposure to water, cooling effects, salinity, and tidal dynamics—are considered when interpreting the performance differences. Given Taiwan's high population density and competition for land use, the results highlight the carbon reduction potential of OFPV systems and further support their evaluation as a complementary strategy for expanding solar energy in land-constrained regions.