Ariz. Rev. Stat. § 42-14156
A. The valuation of electric generation facilities referred to in section 42-14151, subsection A, paragraph 4 shall be determined as follows:
3. The valuation of personal property used in operating the facility is the cost multiplied by the valuation factors as prescribed by tables adopted by the department, adjusted as follows:
6. The following apply in determining cost for the purposes of this subsection:
(d) In the case of a facility that is acquired from another taxpayer:
7. The department shall not value personal property construction work in progress until the property is first placed in commercial service. For the purposes of this paragraph, "commercial service" means:
B. For the purposes of this section: