Transformation concepts for factories are an integral aspect of the ongoing global energy transition. Identifying emission sources and substituting them with green energy solutions remains a complex task. While regulatory pressure urges compliance with climate goals, investment decisions require satisfactory financial returns to be realized. This paper introduces a five-step brownfield methodology addressing transformation of energy supply systems to support net-zero production. It focuses on selecting potential transformation scenarios based on supplementary solution modules and further environmental and economic criteria, using the solution modules to assist transformation planning. The methodology is applied to an exemplary use-case.