In the present study, an integrated planning model was developed to find economically/environmentally optimized paths toward future smart electricity systems with high level penetration of intermittent renewable energy and new controllable electric devices at the supply and demand sides respectively for regional scale. The integrated model is used to (i) plan the best power generation and capacity mixes to meet future electricity demand subject to various constraints using an optimization model; (ii) obtain detailed operation patterns of power plants and new controllable electric devices using an hour-by-hour simulation model based on the obtained optimized power generation mix. As a case study, the model was applied to power generation planning in the Tokyo area, Japan, out to 2030 in light of the Fukushima Accident. The paths toward best generation mixes of smart electricity systems in 2030 based on fossil fuel, hydro power, nuclear and renewable energy were obtained and the feasibility of the integrated model was proven.