Abstarct: The lack of investment in the electricity sector has created a major bottleneck in the continuous flow of energy in the market, which will create many problems for the sustainable growth and development of modern society. The main reasons for this lack of investment are the investment risk in the electricity sector. So we must look for a way to reduce this risk. One of the ways to reduce portfolio risk is to diversify it. This study applies the concept of portfolio optimization to demonstrate the potential for greater use of renewable energy (including wind, solar and hydro technologies), which reduces the risk involved in investing in the electricity sector. The research also shows that investing in renewable energies can offset the risk associated with total input costs. Such costs stem from the volatility of fossil fuel prices, investment costs, repair and operation costs, and environmental costs. For example, this case study shows that Iran could theoretically supply about 33 percent of its electricity supply from renewable energy sources compared to its current 15 percent share. The study suggests that instead of costing, consider the forecast of electricity supply and risk minimization that will result in an increased supply of renewable energy in the market.