Idaho Code § 61-502A
Except upon its explicit finding that the public interest will be served thereby, the commission is hereby prohibited in any order issued after the effective date of this act, from setting rates for any utility that grants a return on construction work in progress or property held for future use and which is not currently used and useful in providing utility service. Except as authorized by this section, any rates granting a return on construction work in progress or property held for future use are hereby declared to be unjust, unreasonable, unfair, unlawful and illegal. When construction work in progress is excluded from the rate base, the commission must allow a just, fair and reasonable allowance for funds used during construction or similar account to be accumulated, computed in accordance with generally accepted accounting principles. If the commission sets rates for any utility including a return on property held for future use and subsequently determines that such property is not needed to provide utility service, then the commission shall determine whether any gain or loss occurring from the sale or other disposition of the property may be included in the utility's rates.
Idaho Code § 61-502A