In this paper, the modeling and simulation of a solar and biomass powered organic Rankine cycle (ORC) system under part load behavior is presented. The model combines the turbomachinery equations for the pump and turbine with the energy equations of the other ORC components to find the net electrical power for a given demand. In addition, exergy based thermoeconomic analysis is applied to determine electricity cost throughout the year. As a case study, the electricity demand of a farm is considered to be supplied from an on-site ORC system and the electrical power grid. The electrical demand of the farm varies in the range of 0-15 kWe and the electrical power output of the ORC can change between 5 and 10 kWe. A comparison between using both the ORC system and the electrical power grid and only the electrical power grid is done in terms of performance and cost. The case study showed that supplying electricity demand with both the ORC and the electrical power grid costs $5238.6 per year, which is 30% more profitable than that with only the electrical power grid.