Based on the cumulative exergy analysis method, the effect of incorporating the Ice Thermal Storage (ITS) air conditioning system in power supply is analyzed. Not only the cumulative exergy of air conditioning system is considered, but also that of the processes consuming the power generated by the same peak regulating unit. The results show that the total cumulative exergy consumption of all processes consuming the power supplied by the peak generating unit, increases as the ITS system is applied. However, the average cumulative exergy variation, which is the ratio between the increment of the cumulative exergy consumption (Delta CEx) and the cooling load of the ITS system (Q(ITS)), decreases slightly as Q(ITS) increases. It exhibits a linear relationship with the operating load of the power generating unit and Q(ITS). And, it decreases as either of the two parameters increases. These results are verified by two case studies. (C) 2011 Elsevier Ltd. All rights reserved.