Purpose – This paper aims to propose a decision support tool that would aid decision-makers to implement energy-saving measures effciently in a corporate real estate. Design/methodology/approach – The tool consists of a system dynamic model that allows describing and quantifying the complex interaction between potential maintenance scenarios, external energy factors and case-specifc conditions. In addition, to include the uncertainty of some of the input variables related to the external energy factors, Monte Carlo simulation has been applied. Findings – A case study of a city hall in The Netherlands showed the usability of the proposed tool. Over the selected period of 20 years, applying the chosen set of interventions, the simulation showed possible gains in the net present value and signifcant decrease of energy consumption and carbon emission. Municipal offcials and consultants verifed the tool for energy effciency. Research limitations/implications – Although the tool has proved its functionality in one case study, to test its robustness, additional case studies would be preferable. Practical implications – The assessment tool can help organizations in assessing energy-effcient maintenance scenarios that include multiple technical energy effciency interventions as a part of other maintenance activities. Originality/value – There are numerous ways to increase building’s energy effciency, but a lack of knowledge is often hindering the enhancement of maximal benefts. A tool that would assess both fnancial and environmental benefts of potential technical intervention would provide useful insights into corporate’s real estate current and possible future energy performance. This would aid corporations in making better decisions regarding fnances, and on the long run, it will bring an improved corporate image.