In calculating its revenue requirement under Section 58-27-2730, and apart from the recovery of a return on construction work in progress, an electric utility may not include in plant service its investments in any new electric generating facility of more than two hundred fifty megawatts, or the costs associated with operating such a facility, except through a general electric rate proceeding under Section 58-27-860 and Section 58-27-870 or through a contested case proceeding for the limited purpose of establishing the prudence of the facility under this section.