Any municipality or county commission operating a waterworks or electric power system under the provisions of this article shall set up and maintain a proper system of accounts in accordance with the requirements of the Public Service Commission, showing the amount of revenues received from such waterworks or electric power system and the application of the same. At least once each year such municipality or county commission shall cause such accounts to be properly audited, and a report of such audit shall be open to the public for inspection at all reasonable times.