An assessment is presented of the evaluation of the application of cool storage air-conditioning (CSA) in the commercial sector as a resource in the electricity generation expansion planning. The resultant impacts of analysis of emission costs on annual emissions from power generation are also discussed. A building energy simulation tool is used for assessment of potential savings and peak load shifting of CSA application in commercial buildings. In this study, an integrated resource planning (IRP) model is used to evaluate the economic effectiveness of the CSA option. The IRP analysis with emission costs results in deferring the installation of four units of 1000-MW coal-fired power plant from 2010 to 2011, and one unit of 1000-MW coal-fired power plant and one 200-MW CSA option are removed from the IRP plan. Results show that the CSA option is a viable resource in the least-cost planning and reducing environmental emissions. (C) 2001 Elsevier Science Ltd. All rights reserved.