This study aims to develop an evaluation process for comparing the energy performances of Green and non-Green buildings. The information on the building attributes and energy consumption of 455 multi-family housing complexes (MFHCs) in 2014, including 321 non-certified MFHCs and 126 MFHCs that accredited Green Standard for Energy and Environmental Design (G-SEED) certification (an official Green Building certification in South Korea) and 8 MFHCs that accredited Leadership in Energy and Environmental Development (LEED) certification, were applied to the empirical study. Data-mining techniques are applied to develop the comparison groups considering various building attributes, and the database was classified into four groups based on the average enclosed area per household (AEA). It was shown that the large-AEA groups (i.e., Group 4, over 143.47 m(2)) had less energy use intensity (EUI) than the small-AEA groups (i.e., Group 1, under 97.04 m(2)). The mean of site EUI for Groups 1, 2, 3, and 4 were significantly different (125.29, 116.35, 110.89, and 101.00 kWh/m(2).y, respectively). While the G-SEED and LEED-certified MFHCs were considered to have up to 10 and 15% energy savings, respectively, compared to all non-certified MFHCs, the comparative analysis by the developed Groups 1, 2, 3, and 4 revealed that the G-SEED-certified MFHCs and the non-certified MFHCs had no significant differences in energy performance. Therefore, the energy performance rating system of G-SEED should be revised. The proposed energy performance evaluation process can also be useful in identifying the energy performance of other buildings. (C) 2016 Elsevier Ltd. All rights reserved.