This project aims to democratize distributed energy systems design and empower building owners with trustworthy information for holistic analysis of sustainable technologies. It will be accomplished through the creation of an open-source development community for building energy supply models at an urban scale, with a specific focus of adoption by Swedish municipalities and energy companies. The vision is to apply the models in online maps, like existing solar maps, and provide recommendations on a selection of sustainable technologies – solar photovoltaics, electric vehicles and chargers, batteries, and heat pumps. The project will have impact on multiple levels and stakeholders, and the open-source approach aims to encourage collaboration and contribution from researchers, commercialization by firms, adoption by municipalities, and most importantly, to ensure that homeowners can have the greatest impact on sustainable and secure energy supply with their limited budget.