Concerns over the rising energy consumption and CO₂ emissions of the expanding cloud market necessitate urgent sustainability improvements. However, there are no coherent studies on the costs and benefits of sustainability measures for cloud infrastructures. To investigate the value of renewable energy and excess heat utilization, we propose a mixed-integer programming model for cost-minimal cloud infrastructure network planning. We apply our model to a German case study and find significant potential for carbon footprint and cost reduction associated with excess heat utilization.