Based on historical data concerning the development of policies and the deployment of RES-H technologies, it is not possible to derive conclusions about the actual impact of different support schemes; other crucial aspects like fuel price developments, macroeconomic processes and crises, public awareness, impact of information campaigns, trainings, etc. would have to be included in the analysis. This was not in the scope of this paper. Examples for quantitative assessment of future impacts of RES-H policies are presented in other papers of this special issue.