It is expected that power generation systems utilizing solar energy and technologies of capturing carbon dioxide (CO₂) from stack gas should be introduced under constraints of CO₂ emission in the future. In this paper, characteristics and economics of power generation systems utilizing solar energy are evaluated and compared with those of an integrated coal gasification combined cycle plant (IGCC) when carbon tax is imposed as an economic penalty for CO₂ emission. The investigated power generation systems utilizing solar energy are as follows: a solar photovoltaic system (PV system) and a hybrid power generation system utilizing solar thermal energy (HB system) which has been proposed by the authors. The cases of capturing CO₂ for the HB system and the IGCC are also investigated. The location of the systems is assumed to be Ottawa where the total horizontal solar radiation energy is approximately as same as the world average. It has been shown that the unit cost of the HB system without capturing CO₂ is lower than that of the IGCC when the carbon tax is 3_??_4×10⁴ yen/t-C. The CO₂-capturing HB system can be economically preferable when the carbon tax is raised to 4_??_5×10⁴ yen/t-C. The economics changes considering the uncertainty of system construction costs and fuel cost have also been investigated in the paper.