Streamlining structural engineering compliance of rooftop solar photovoltaic installations using an open-source approach

• Regulations often slow solar photovoltaic (PV) penetration velocity. • Rooftop PV sometimes requires both interpretation and approval from a professional engineer. • This engineering process is a substantial fraction of the capital costs of small-scale PV systems. • New open-source tool to streamline the process while maintaining building code compliance. • Average 5 kW rooftop PV systems cost reduced 5–25 % in the U.S. using free tool. Although solar photovoltaic (PV) systems provide the lowest cost electricity, regulations often slow PV penetration velocity. A current hurdle to distributed generation with PV is building code compliance. For example, installing solar PV modules on rooftops in some areas requires both interpretation and approval from a professional engineer. This engineering process comes with costs, which can be a substantial fraction of the capital costs of small-scale systems for smaller or efficient houses, as well as for less-wealthy families that want to build up systems one module at a time. Improving the permitting and inspection process can thus significantly reduce the soft costs of distributed PV systems. This study provides a method of overcoming these challenges for rooftop solar PV by introducing an open-source tool to streamline the process while maintaining compliance with necessary local building codes. The results of economic analysis on this method show costs of average 5 kW rooftop PV systems can be cut by 5–25 % in the U.S. Thus, accessibility and affordability of rooftop PV systems are significantly improved because of the elimination of redundant engineering. Implementing such open-source tools is a low-cost effective area of future energy policies to facilitate more economically inclusive and widespread PV adoption.