Top-Down calculation methods use data compiled per sector or nation as a starting point for the appraisal of the extent of energy saved. Data expressed per annum have to be adjusted by balancing external influence factors such as heating degree days (HDD) resp. cooling degree days (CDD), structural changes, product mix etc. in order to achieve a trustworthy impression on the overall improvement of energy efficiency.
Top-down methods do not provide precise detailed measures, nor do they demonstrate causal inter-relation between measures and energy savings caused by them. On the other hand, they often are more simple and cheaper and as they are able to show development trends, they often get referred to as „energy efficiency indicators“.
When developing top-down calculation schemes, according to the Energy Efficiency and Services Directive to the highest possible degree existing methods such as the model ODEX have to be applied. The Austrian Energy agency as a partner in the ODYSSEE project contributes to the further development and ongoing updating of the ODEX model; energy efficiency indicators developed in this project will be adopted by the energieeffizienz monitoringstelle („energy efficiency monitoring unit“) as much as possible and adapted whenever necessary.