The objective of this study is to develop a methodology for estimating the investment costs for heat collection systems gathering excess heat from complex industrial sites and delivering it to a DH (district heating) network. The paper presents a case study conducted on Sweden's largest chemical cluster. In a previous paper, the economic feasibility of delivering heat from the cluster to a regional DH system proved to be favorable under a wide range of price conditions. We develop the methodology used previously in order to identify how each of the plants should contribute to the heat delivery in order to achieve the lowest total investment cost within the cluster. The optimization problem is formulated with the constraint that each plant delivers heat to the DH network separately and at the temperature required by the network. Investments for heat collection systems were estimated for the current configuration of the cluster's energy system (Base case) and for two possible future configurations with increased levels of internal heat recovery. The resulting optimal contribution mix provides a detailed overview of how the plants compete at different specified levels of DH delivery. In the Base case, two plants strongly compete due to similar investment costs.