This study aims to measure the expected utility gains resulting from the expansion of renewable energy sources for power generation, considering both their costs and the volatility of prices. By applying Modern Portfolio Theory, which enables a comparison of economic benefits while accounting for price volatility and uncertainty, this study provides robust economic evidence supporting the expansion of renewable energy for power generation. Our findings emphasize the crucial role of renewable energy sources, such as solar and wind, in mitigating electricity mix risks at local level in South Korea. Furthermore,
this study establishes a quantitative economic foundation for the expansion of renewable energy, advancing beyond the existing rationale that primarily justified such expansion solely on environmental and ethical considerations.

[Key Words] Power Generation Mix, Modern Portfolio Theory, Price Volatility