(1) If the contractual parties have not agreed otherwise, and subject to other provisions, operating costs are to be apportioned in proportion to the residential floor space. Operating costs that depend on recorded consumption or causation by the lessees are to be apportioned according to criteria that take into account the differing consumption or causation.
(2) If the contractual parties have agreed otherwise, the lessor may by declaration in text form specify that, contrary to the agreement reached, the operating costs in future may be apportioned as a whole or in part according to a criterion that takes into account the recorded differing consumption or the recorded differing causation. The declaration is permissible only prior to commencement of an accounting period. If the costs previously have been included in the rent, the rent is to be reduced accordingly.
(3) If premises for which title is held by an owner are let on a lease and the contractual parties have not agreed otherwise, then in derogation from subsection (1) the operating costs are to be apportioned in accordance with the criterion applying to the allocation scheme in place between the owners of residential properties. Where this criterion is not in keeping with the principle of equitably exercising discretion, the apportionment is to be performed in accordance with subsection (1)
(4) An agreement deviating from subsection (2) to the disadvantage of the lessee is ineffective.