A simplified estimation model for determining the optimal rooftop photovoltaic system for gable roofs

•Developed model can evaluate the profitability of rooftop PV system for gable roofs.•Absolute and relative investment value of PV system was analyzed using NPV and SIR.•Design parameters were considered in developing the simplified estimation model.•The optimal rooftop PV system was determined by region and design parameters.•It can help decision-makers to determine optimal rooftop PV system for gable roofs.

This study aimed to develop a simplified estimation model for determining the optimal rooftop PV system for gable roofs that can evaluate life cycle economic and environmental assessment, by considering the type of installation to be used for such rooftop PV system. The military facilities located in three regions (i.e., Gimpo (northern part), Deajeon (middle part), and Pohang (southern part)) in South Korea were selected for the case studies. The results of this study are as follows. First, in terms of NPV25 (net present value in 25 years), for the roofs with a lower orientation, ToI-2opt. was selected as the optimal rooftop PV system, and for the roofs with a higher orientation, ToI-2ext. or ToI-3opt. was selected as the optimal rooftop PV system. Second, in terms of SIR25 (savings-to-investment ratio in 25 years), for the roofs with a lower orientation, ToI-1ext. was selected as the optimal rooftop PV system, and for the roofs with a higher orientation, ToI-3opt. was selected as the optimal rooftop PV system. The simplified estimation model may be useful for decision makers, including experts and non-experts (i.e., architects, owners, construction managers, etc.), or policymakers in determining the optimal rooftop PV system for a gable roof.