A nonlinear model, called TOOCS-off,1 has been developed in this paper for optimal operation of combined heating, cooling, and power systems. The system includes combined heating power (CHP) module, auxiliary boiler, absorption chiller, heat storage unit, utility grid and electrical, thermal, and cooling loads. In fact, by solving this offline model, we will determine t optimal energy flow regarding both the amounts of electric, thermal, and cooling loads in each time interval and prices of electricity sold to costumers or purchased from utility, and prices of heating and cooling. In the cost function of this model, the total economic benefit of this system is maximized during total daily operation time. The results of an optimal operation model have been discussed techno-economically and a case study has been investigated.