The present study focuses on optimal sizing of an integrated renewable energy (IRE) system with battery bank to meet the load demand of a cluster of four zones in Karnataka state of India. Hourly load demand has been simulated using HOMER software based on three scenarios - high investment with low (HILR) rating appliances, medium investment with moderate (MIMR) rating appliances, and low investment with high (LIHR) rating appliances. Simulation results of optimal size, total net present cost (TNPC) and cost of energy (COE) have been obtained using genetic algorithm (GA) considering different scenarios with and without DSM strategy by keeping energy index at 1. Results of three scenarios with DSM strategy were compared with those without DSM strategy. Based on the comparison of the results, scenario of HILR with DSM strategy is found to have minimum TNPC and COE for zone 1 and zone 2, while scenario of MIMR with DSM for zone 3 and LIHR with DSM for zone 4 are found to have least TNPC and COE. Further, obtained results of TNPC of GA have been validated by comparing PSO technique. It has been observed that, results of GA and PSO were found to be almost same.