Every municipal electric utility and every electric cooperative are hereby authorized to use surplus revenues in connection with the exercise of any power or authority they may exercise under any law; provided, that the exercise of that power or authority is not a violation of the terms and conditions of a wholesale power contract between the Tennessee Valley authority and the respective municipal electric utility or electric cooperative and is not a violation of or otherwise prohibited by the terms and conditions of any covenants in any outstanding revenue bonds of the municipal electric utility or loan covenant of the electric cooperative, as may be applicable.