Abstract The sociology of technological expectations examines, amongst other questions, the way in which expectations of new technologies help to mobilise or hinder commitment and investment. In this and other regards, studies have referred to a ‘sea’ of informal, individual expectations, contrasting these with formal visions such as roadmaps. Here we first identify and document those less formal, individual expectations of static and mobile applications for hydrogen fuel cells (H2FCs), as held by innovation system actors. We then show that these typically involve conditionalities and uncertainties that relate as much to policy and society as to technology. In contrast, formal roadmaps set out bold possibilities premised on heroic policy assumptions that elide the social and policy uncertainties that informal expectations admit to. We argue that there is policy value in informal expectations: that they reveal issues that need to be addressed and conditions that need to be met. Moreover these are often social and political, as well as technological. We illustrate the variety of such issues with expectations-related data from interviews with 145 hydrogen fuel cell innovation system actors in Spain, Germany, Slovenia, France and the UK.