(a) Except as provided in subdivision (b) of this section, the cost of initial improvements (including repairs, rearrangements, additions and betterments) to property leased from others made in the course of preparing the property for service, and the cost of any subsequent additions or betterments to such leased property shall be charged to the steam plant or other property account appropriate for the class of property leased. (See account 101 and operation and maintenance instruction, section 467.5 of this Article.)

(b) When the initial improvements to leased property which are otherwise chargeable to steam plant or other property accounts are of relatively minor cost or short life, the cost shall be charged to the account in which the rent expense is included. If the period of the lease is not more than five years, the cost may be carried in account 146, Other Deferred Debits, and charged off over the period of the lease to the account in which the rent expense is included. (See also operation and maintenance instruction, section 467.5[e] of this Article.)