Solar-aided coal-fired power generation system is the integration of solar energy and conventional coal-fired power system. The first stage extraction from turbines was replaced by solar energy to heat feedwater, so that the replaced high pressure steam can continue to work in Rankine cycle. Thermo economic structural theory was applied to perform a comparative study between the fuel-saving mode and power-boosting mode of SAPG (solar aided power generation) system. The physical and productive structures of systems were built to describe the interactions of all components in the system. Then thermo-economic costs of each component were calculated on the basis of exergy analysis. The results showed that compared to coal-fired power generation system, coal consumption rate is decreased by 15.04 g/kWh in fuel-saving mode. The power output is 57.2 MW higher in power-boosting mode. The unit thermo-economic cost of electricity is increased by 16.9-21.6% due to the large investment of solar collector field. Although the cost of solar energy is considered free, the thermo-economic cost of solar energy was found to be very high because of this large investment. Analysis of the condenser suggested that the exergy cost of condenser is all of irreversibility and thermo-economic cost of condenser is made up of irreversibility and investment. (C) 2016 Elsevier Ltd. All rights reserved.