As heat demand of buildings accounts for a significant amount of final energy use and related carbon emissions, it's important to gain insights into the homeowners' decision-making processes and to identify factors determining the choice of heating systems. In this study, data was collected in an online survey carried out in 2015, from private homeowners of existing and newly built single and double-family houses in Austria who had invested in a new heating system within the last ten years (N=484). In contrast to previous studies, this study specifically investigates the triggers behind homeowner decisions to invest in a new heating system (e.g. problem, opportunity, or new building situation). Results of binary logistic regression analysis show that subsidies for heating system tabinvestments and infrastructural adjustments reveal to be most effective for homeowners in problem situations to foster alternative heating systems. For homeowners in opportunity situations (e.g. building refurbishment), in addition operational convenience appears to be important. For new buildings, the main barriers for alternative heating system adoption were found in the positive perception of fuel supply security and feasibility of fossil systems. Thus, the use of trigger-specific policy measures is proposed to foster alternative heating systems in the residential building sector.