A large-scale installation of renewable energy sources（RES） such as photovoltaic（PV） and wind power generation causes new problems in power system operation， for example reverse power flow by surplus power and insufficient capacity to regulate system frequency and node voltage. As one of the countermeasures against such uncertainty problems due to output fluctuations of RES， concepts named vehicle to house（V2H） or vehicle to grid（V2G） by using electric vehicles（EVs） as energy storage will play an important role and also it is indispensable for us to establish the evaluation approach of the usage of EVs. In this research， we selected a smart house equipped with PV generation and an EV， and quantitatively evaluated the effects of charging and discharging the EV's battery on domestic consumption rate of PV output， electricity cost of the house， and the amount of CO2 emission. As a result， the reverse power flow and CO2 emission were reduced by effective utilization of PV generation and the EV's battery. Finally， contribution of EVs for energy management of aggregated houses（a multi-house community） was also investigated and verified by simulation.