The demand charges and the blocks in the energy charges set forth in the rate schedules are based on billing periods of approximately one (l) month. In the case of the first billing of new accounts (temporary service, cotton gins, and other seasonal customers excepted) where the period covered by the billing involves fractions of a month, the demand charges and the blocks of the energy charge will be adjusted to a basis proportionate with the period of time during which service is extended.
(1970 Code, § 13-321)