No supplier of electric power or gas shall be liable for (a) actions taken pursuant to an order of the commission, or by reason of curtailment of such electric or gas service pursuant to such order or its curtailment plan on file with and approved by the commission; or (b) inability of a supplier to furnish adequate or sufficient supplies of electric power or gas or refusal to supply electric power or gas when such inability or refusal is due to inadequate or insufficient supplies on the supplier’s system occurring as a result of the supplier’s being unable to obtain from the commission an order which allows adequate time to construct necessary generating and transmission facilities.