Although considerable venture capital investment has been made in cleantech since the early 1990s, the performance of the vast majority of these funds has been extremely poor. Early-stage capital has now become much scarcer in the sector, such that early-stage companies are finding it hard to raise finance, even with apparently compelling technologies and markets. Our client, a regional clean energy organisation wanted to understand better the underlying reasons for this market failure, with a view to proposing a new approach to providing such funding in the future. E4tech interviewed fifteen investors from our international network of contacts in the cleantech investment space, including VC practitioners, investment advisors, and early-stage company supporters. We also reviewed data and literature on the performance and priorities of previous investments. We brought this information together to draw out conclusions on the weaknesses of current approaches for cleantech investment, and alternative new approaches to investment vehicles that could overcome them.