The conventional pricing mechanism used for electricity systematically hides huge investment risks which are embedded in the overall cost of production. Although consumers are often unaware of these risks, they present a large financial burden on the economy. This study applies the portfolio optimization concepts from the field of finance to demonstrate the scope of greater utilization of renewable energies (RE) while reducing the embedded investment risk in the conventional electricity sector and its related financial burden. This study demonstrates that RE investment can compensate for the risks associated with the total input costs; such costs being external volatilities of fossil fuel prices, capital costs, operating and maintenance costs and the carbon costs. By means of example, this case study shows that Japan could in theory obtain up to 9% of its electricity supply from green sources, as compared to the present 1.37%, based on the utilization of a portfolio risk-analysis evaluation. Explicit comparison of the monetary values of the investment risks of conventional and renewable energy sources shows that renewable energies have high market competitiveness. The study concludes with a recommendation that, as a business objective, investors would benefit by focusing on electricity supply portfolio risk minimization instead of cost. This could also inherently increase the supply of renewable energy in the market. (C) 2010 Elsevier Ltd. All rights reserved.