Wisconsin Statutes Taxation (Ch. 70 to 79) § 70.1105. Taxed in part

(1) Property that is exempt under s. 70.11 and that is used in part in a trade or business for which the owner of the property is subject to taxation under sections 511 to 515 of the internal revenue code, as defined in s. 71.22(4m), shall be assessed for taxation at that portion of the fair market value of the property that is attributable to the part of the property that is used in the unrelated trade or business. This section does not apply to property that is leased by an exempt organization to another person or to property that is exempt under s. 70.11(34).

(2) Property, excluding land, that is owned or leased by a corporation that provides services pursuant to 15 USC 79 to a light, heat, and power company, as defined under s. 76.28(1)(e), that is subject to taxation under s. 76.28 and that is affiliated with the corporation shall be assessed for taxation at the portion of the fair market value of the property that is not used to provide such services.