In determining costs for an extension or conversion included in the cost and feasibility report required by section 50-2506, Idaho Code, the public utility shall be entitled to amounts included in applicable tariffs, rules or regulations filed with or promulgated by the Idaho public utilities commission or federal communications commission or federal energy regulatory commission. In the event tariffs, rules and regulations do not apply, the public utility shall be entitled to amounts sufficient to repay them for the following, computed according to the uniform system of accounts approved by the Idaho public utilities commission or other appropriate regulating agency, and in the event the public utility is not subject to regulation by governmental agencies, by the utility corporation's system of accounts then in use and in accordance with the accounting procedures of said public utility:
Idaho Code § 50-2515