International political negotiations and national policy for climate change mitigation are increasingly focussed on the mobilisation and scale up of investments in clean energy infrastructure. This paper aims to develop the understanding of how institutional investors in the private sector perceive barriers to scaling up investment into clean energy infrastructure and what policy solutions to those barriers they advocate. This paper adds to existing scientific knowledge through a clear focus on private sector perceptions. Through the analysis of previous public statements from organisations and coalitions in the finance sector a number of investment barriers were identified. These initial barriers fed into a Delphi process. The outputs of the Delphi process were categorized into five sets of barriers and a number of policy solutions associated with investing into clean energy solutions. We conclude that there is a need for better engagement with the institutional investment community to ensure further effort on policy development that underpins investments at scale is effective and efficient.