The objective of this study is to evaluate the predictive accuracy of lighting energy consumption carried out by the EnergyPlus program and by the integrated simulation method (ISM), using the Daysim program. EnergyPlus calculates the interior illuminance based on the split-flux and radiosity method, and overestimates the interior illuminance, and we can see large differences in the EnergyPlus interior illuminance results. MBE by the split-flux method was found to range between 81.5% and 463.4%, and the largest MBE occurred at the deepest point. The Daysim program calculates the interior illuminance based on the ray-tracing method, and the largest MBE is -18.9%, at the middle point of the room. Lighting energy consumption differences are caused by the interior illuminance calculation algorithms in the simulation programs. As a result, the lighting energy consumption derived by the EnergyPlus program without ISM is approximately 34.6% smaller, than that of real consumption. The ISM was improved in the prediction accuracy of lighting energy consumption by 24.6% in absolute value. The results of the lighting energy consumption with ISM are relatively more accurate than the EnergyPlus results without ISM, because the modified lighting schedule is similar to the actual situation. (c) 2012 Elsevier B.V. All rights reserved.