Information asymmetry between building owners and suppliers of sustainable building renovations threatens to slow the energy transition. This study introduces the concept of a Digital Energy Advisor (DEA) which autonomously and transparently provides personalized guidance in an educational way about the technical, economic, and environmental aspects of sustainable buildings. The technical requirements of building a DEA are described, including model structure and input data, which connects to the barriers found in being able to realize such a tool available to the public. It is shown that while it is technically possible, data procurement costs, personal privacy via GDPR, and the intellectual property of private firms establish the limits for creating a non-profit, publicly accessible DEA. Technical and commercial pathways around the barriers are discussed, and the conclusion is that an open-source business model has the greatest potential for a public DEA.