In Duke Energy Arlington Valley, LLC v. Ariz. Dep't of Rev., 219 Ariz. 76, 80, P 18, 193 P.3d 330, 334 (App. 2008), taxpayers who were operators of electric generation facilities sought a declaratory judgment to establish that depreciation tables for valuation of electric generation facilities adopted by the Department of Revenue were rules under the APA and thus subject to the relevant rulemaking requirements. Id. at 77, P 2, 193 P.3d at 331. The tax court held that the tables were not rules. Id. at P 3. The Court affirmed, concluding that the depreciation tables were not rules because they were referred to as guidelines in the statute and they were "only one element" used by the Department of Revenue in determining the statutorily mandated value of electric generation facilities. Id. at 78-79, PP 11, 15, 193 P.3d at 332-33.