This paper focuses on optimal operation schedule of a Microgrid that is interconnected to the power grid. We develop a mathematical model to compute the optimal operation schedule that embodies demand response. Integer Programming optimization is used to this end. Our model incorporates the electricity load into three types: fixed, transferable, and user-action loads. The transferable load plays a key role in molding demand response. Experimental results show that the proposed model exploits the demand elasticity and significantly reduces the total operation cost. Also observed from the experiments are the impact of the uncertainty in renewable distributed generators on operation schedule and total cost and the role of power storages for enhancing the demand elasticity with respect to user-action loads and for reserving power against high price.