In a developed economy, improving the energy performance of the industry sector can make an important contribution to achieving national energy efficiency goals. Policy measures aimed at increasing energy efficiency in industry must be proven to be effective. In Ireland one such measure is the Large Industry Energy Network (LIEN) programme. LIEN is a voluntary network of large energy users, facilitated by the national energy agency, working to maintain strong energy management practices. In this paper, we combine top-down methods for analysing national energy statistics with company-level figures supplied by LIEN participants to quantify the energy savings achieved by the companies and to determine the fraction of national savings that can be attributed to them. By comparing the collective performance of participant companies with the performance of the rest of industry we provide an indication of the effectiveness of the programme and quantify the savings that may be directly attributable to it. These figures when combined with national energy forecasts for industry help us assess the likely contribution of the programme to future national energy savings targets.