This article presents the case of a policy invention where various kinds of entrepreneurship and a window of opportunity played important roles. In 2008 the EU adopted a new Carbon Capture and Storage (CCS) policy with an inventive funding instrument at its core: the NER 300 fund, based on revenues from the auctioning of emissions trading allowances. Thus far, the literature on policy entrepreneurs has focused more on success factors that enable particular persons to be especially influential than on the defining characteristics of entrepreneurship. We contribute to the literature on entrepreneurship and windows of opportunity by distinguishing two entrepreneurial techniques – framing and procedural engineering – and two categories of commitment – ‘tortoise’ and carpe diem. We conclude that ‘tortoises’ who contributed to creating the broad and general climate policy window paved the way for issue-specific carpe diemers who promoted the more specific NER 300 policy invention. Furthermore, we distinguish and discuss four different entrepreneurship mechanisms that may influence policy invention processes.