Impacts and cost-effectiveness of major energy efficiency policies for existing buildings: what do we exactly know and what can we learn?

There have been many reviews about how energy efficiency policies for existing buildings work, but more rarely about the details of their effective impacts and costs, mainly due to difficulties in accessing data. The National Energy Efficiency Action Plans enable to know what policies are implemented and how. But details about their impacts and costs can often be found in national language only, and rarely in a single report (if available at all). This paper presents an analysis of ex-post evaluations and monitoring reports available for 13 major energy efficiency schemes for retrofitting buildings. The first part reviews the data about evaluation methods, energy savings, and costs. It describes the main data found and discusses to what extent these data can be compared. This stresses the need for in-depth study to correctly analyse the data. The second part proposes a methodology to compare results and costs of different policies, illustrated by one pilot comparison between the Italian and the French tax credit schemes. This example shows the importance to take into account the differences in the scope and methods used to estimate the impacts and costs when comparing indicators such as cost-effectiveness ratios. The paper concludes with a discussion about the need to promote information sharing between the Member States and evidence-based approaches for the design and management of energy efficiency policies.