Integration of top-down and bottom-up methods
The objective of integrating the evaluation methods is to accurately measure the energy savings achieved under the EU Directive using both: bottom-up and top-down approaches.
Both evaluation methods have certain advantages and drawbacks, i.e. there is a trade-off between accuracy and the costs of evaluation. Combining top-down and bottom-up evaluation allows for cross-checking of the achieved results, and can therefore lead to higher accuracy and/or lower costs.
Both in bottom-up and top-down evaluation, so-called correction factors have to be taken into account, that may bring additional uncertainty to the results. For example, it is difficult to assess multiplier effects (indirectly induced further savings due to achieved higher market shares of energy-efficient technologies and solutions) using bottom-up evaluation. On the other hand, it is challenging to distinguish autonomous savings from a top-down indicator. Furthermore, the availability of data and evaluation tools differs among Member States, i.e. a specific mix of top-down and bottom-up methods is required for each country.
Therefore, the development of an integrated set of bottom-up and top-down methods is essential in order to improve the accuracy of measurement results and thus make a credible assessment of how the Member States could attain the 9 % savings target by 2016.
The project report dealing with the integration of the two evaluation approaches can be accessed here:
Harmonised calculation of energy savings for the EU Directive on energy end-use efficiency and energy services: development and assessment of a combined bottom-up and top-down approach