A prepayment installment decision support framework in an inventory system with all-units discount against link-to-order prepayment under power demand pattern

•This paper proposes an installment plan to pay when an all-units discount is offered.•Clients’ demand is interconnected with time and price multiplicatively.•A transaction cost is incurred to accomplish a prepayment installment to the supplier.•Profitable and nonprofitable cases are explored considering all purchased quantities.•It is profitable to do the prepayment through a single installment.