The consumer may elect, upon application, to pay for electric service under Schedule R only on a levelized billing arrangement by which the estimated monthly billings for a twelve-month subsequent period will be averaged for monthly payments. Any levelized arrangement shall be initiated only during the months of May and August and only upon complete payment of any outstanding electric service billings. In the event that service is terminated due to nonpayment of rendered billings, in accordance with regulations of the Utilities Department, or at the consumer's request for any reason of his or her or her choosing, any differences between the actual and levelized billings shall be immediately due and payable to the Wapakoneta City Utilities Department or reimbursable to the consumer.