Who invests in energy efficiency in owner-occupied homes in Germany? A configurational analysis of personal and contextual conditions

Achieving high levels of energy efficiency in owner-occupied houses is essential for reaching the European Union's sustainability goals. The question is how to increase those efficiency levels. We use a novel approach to study personal and contextual drivers of energy-efficiency investments in owner-occupied houses in Germany. We conduct fuzzy set Qualitative Comparative Analysis (fsQCA) based on a dataset of 498 owner-occupants of houses in Germany. With this unique approach, we find that owner-occupants who invest in energy efficiency are highly educated, live in large households with an Energy Efficiency Culture (EEC), and have moved rather recently. Furthermore, being a young owner, being highly subsidized, having a high income, or having investment optimism can differentiate a configuration leading to energy efficiency investments. In two configurations, labeled “excluded” and “opt-outs,” owners do not invest in energy efficiency, but share the conditions of being highly educated and living in large households. In these two configurations, people in the household are on average older, lack an Energy Efficiency Culture, have no investment optimism, and have received none or few subsidies. We identify that Energy Efficiency Culture is a necessary condition for the investment decision. From a theoretical perspective, our findings suggest that, Energy Efficiency Investment Behavior (EEIB) is conjunctural, equifinal, and asymmetric: no single factor drives investment, but distinct combinations of behavioral and contextual conditions are each sufficient for EEIB. This clearly distinguishes our configurational approach from net-effects models. From a policy perspective, our results demonstrate a need for parallel, configuration-specific instruments rather than “one-size-fits-all” measures. Key levers include strengthening EEC for non-investors; targeting subsidies to low-income homeowners; motivating young owners early in their tenure; using efficiency-linked mortgages, especially for high-income households; and expanding alternative financing to increase investment.