An owner who has previously determined the approximate energy usage for a dwelling unit by the use of an energy allocation system, including use of a system before the promulgation of the regulations, shall disclose to a current or prospective occupant: The highest monthly energy cost billed to the same dwelling unit in a month the dwelling unit was leased during the preceding 12 months; The lowest monthly energy cost billed to the same dwelling unit in a month the dwelling unit was leased during the preceding 12 months; The average monthly energy cost billed to the same dwelling unit for the preceding 12 months including only months the dwelling unit was leased for the entire month; and The average monthly energy costs billed to similar sized leased dwelling units in the preceding 12 months. If the owner has not previously used an energy allocation system within the apartment house: The owner shall disclose estimated energy costs in the following priority based on: Actual billing to similar sized dwelling units in other apartment houses within the same apartment house complex, The actual operating experience of the vendor for similar sized dwelling units in other apartment house complexes of comparable age, size, equipment, and geographic location, or A square footage allocation derived from gas or electric bills received by the owner from the utility with a reasonable allowance for common usage and, if necessary, seasonally adjusted; The owner shall provide the estimated energy costs required in §B(1) in terms of an average monthly bill, the highest monthly bill, and the lowest monthly bill.