This study advances the understanding of cleantech commercialisation by adopting a market validation approach to analyse equity capital’s role in navigating the ‘Valley of Death’. Focusing on the three core financial milestones – revenue generation, profitability and retained earnings – we investigate 354 UK cleantech firms over 10years and employ Cox proportional hazard models to explore whether equity capital speeds or slows the achievement of these three financial milestones. We conclude that equity capital-backed firms are slower across the Valley of Death. We discuss the implications of our findings for cleantech firms and those seeking to support the financing of cleantechs.