Most of the European rental housing units need major refurbishments in upcoming years to achieve EU climate protection goals. Because property owners still find it difficult to assess the profitability of energetic retrofitting investments, current renovation levels are far too low. This study contributes to the situation by forming a standardized framework and a tool for calculating the profitability of energy efficiency investments throughout Europe. Findings are based on conducted target group surveys and on a profound literature review. Several relevant areas for energy efficiency investments have been screened, including technical, legal, institutional and financial conditions. It is found that especially market conditions and information deficits harm energy efficiency investments. In line with inflexible regulations, this reduces market incentives that have originally been introduced to trigger market participants. Built on these findings, an online-based tool has been developed to support the decision-making process of each individual investor, regardless the individual knowledge on energy efficiency. The VoFI (Visualization of Financial Implication) method perfectly includes all important and relevant factors, such as financial and tax-related information. As a special technique of financial modelling, it provides all kinds of users with sound decision support in energetic retrofitting activities. The underlying methodology of the tool is presented and major obstacles are identified. Findings are used to define best practices and to assess the transferability between different European markets. The paper contributes to a better understanding on how to tackle information deficits and on implementing sufficient policies to boost energy efficiency investments.