Purpose: The purpose of this paper is to choose the best method for ex ante business model evaluation, improve it and provide a framework to put it into practice. Design/Methodology/Approach: After an in-depth review, we chose the best method for ex ante business model evaluation, improved this method, and applied it to a real case study in which business models had been proposed for a Sustainable Smart District project. Findings: We analysed existing ex ante business model evaluation methods, justifying our choice of the best one. We improved this key question-based method by combining classic management tools and a new, promising procedure. We finally found a strong tool to improve business models before their implementation or, in other words, to improve business model design. Practical implications: The resulting methodology can be applied in a broad range of situations in which a set of business models needs to be evaluated and ordered before making decisions about their implementation. Accordingly, we think it represents a significant contribution to the field of business model evaluation. Social implications: We applied this methodology to a set of business models to be used in a new Sustainable Smart District. This term has gained momentum over the last few years because it is understood to be a good way to combat climate change. Originality/value: We refined and improved an existing methodology for ex ante business model evaluation making it more accurate and credible, and we applied it in the context of a relevant social field, such as the fight against climate change.