In Brazil, as in other countries public utilities are operated as concessions under the coordination of an independent regulatory agency, a role played in Brazil by Aneel– National Agency of Electricity. It is also Aneel s responsibility the estimation of regulatory WACC – weighted average cost of capital of the electricity sector which remunerates investors capital through tariffs until the end of the current tariff review cycle that occurs on average every 5 years. For that the regulator based the calculation of the WACC on American economic data adapted to Brazil reality assuming that data from Brazilian stock exchange series have some limitation. Inaccuracies in the WACC can lead to companies obtaining additional gains in the case of an overestimated rate, or losses in the event of an underestimated, which might result in reduction in investments and could affect the quality of service or expansion plans. Therefore, it is in the interest of society to discuss improvements of the methodology applied in estimating the cost of capital in the sector. This study aims to estimate the weighted average cost of capital of the Brazilian electricity distribution sector through improvements in current methodology adopted by the regulatory agency, aligning it with finance theory best practices. Results indicate the need for deeply discuss from the regulator about some alternatives improvement in the capital structure, risk free rate, country risk and credit risk premium.