The corporation shall be a nonprofit corporation and no part of its net earnings remaining after payment of its expenses shall inure to the benefit of any individual, firm or corporation, except that in the event the board of directors of the corporation shall determine that sufficient provision has been made for the full payment of the expenses, bonds or other obligations of the corporation, then any net earnings of the corporation thereafter accruing from gas properties or rights shall be paid to the municipal gas distribution system or systems for the benefit of which the corporation was organized, and any net earnings of the corporation thereafter accruing from electrical power properties or rights shall be paid to the municipal electrical power distribution system or systems for the benefit of which the corporation was organized.