In order to increase the capacity of renewable energy in power systems, it is necessary to reduce power fluctuations.In this paper, the potential of gas engines (GEs) is evaluated by means of dynamic simulation in hybrid power systems consist of GEs and photovoltaic cells (PV) supply power to a large grid. First, basic characteristics of gas engines were investigated for load changes. The small gas engine, its maximum output is 9.9kW, shows quicker response of output and lower generating efficiency than the gas engine of 350kW output. The load response of both engines is influenced by the amplitude and the frequency of the output demand, and not by the bias load. Next, the simulations were implemented using the real power profile of PV. As a result of simulations, 9.9 kW GE is very useful to compensate PV power fluctuation because of its quick response for the load change. The efficient system to use GEs to achieve both the suppression of the PV's power fluctuation and the higher efficiency of the system is also discussed. By combining a larger scale GE with small scale GEs, the system to control preferentially the small GEs shows higher system efficiency at the same output response condition.