The provisions of this article shall not apply:
to municipally or privately owned plants where a flat charge only is made, and no meters are in operation;
to any municipally owned and/or operated public service utility, the net income of which said utility is used solely for governmental purposes and/or for the discharge of governmental obligations and not for private gain;
to the Tennessee Valley Authority or any municipality that purchases gas, water or electric lights and power from the Tennessee Valley Authority; or
to any state corporation chartered by the State of Mississippi, or any corporation doing business in the State of Mississippi, which buys electric current and/or power from the Tennessee Valley Authority for distribution for domestic and/or commercial purposes.