Demand dispatch (DD) is an emerging key approach for optimal operation of today power distribution systems, which are faced with problems related to challenging technologies. DD enables dispatchable loads (DLs) to commit in dispatching process as well as generating units which are involved in via unit commitment and economic dispatch programs. DD optimizes utilization of demand side assets and diminishes the operation cost. This paper aims to model DD for a smart micro-grid from the viewpoint of DD aggregator (DDA). DDA is a dispatcher devoted to each micro-grid and is responsible for controlling the DLs and also financial relations between power market operator and end users. DDA problem of controlling DLs is formulated as a MILP optimization problem. After that, the proposed model is applied to a micro-grid consisting of 40 houses connected to a 50 kVA transformer and a small hybrid energy system of wind and solar which directly injects its energy into the micro-grid. Moreover, DD is compared with different scenarios of conventional operation modes and it is demonstrated that using DD in comparison with only supply dispatch diminishes the operation cost about 4–25 percent and reduces required capacity of distribution transformers.