Public opposition to new energy technology can harm the chances of successful deployment. Less is known about knock-on effects on the wider energy system, including whether such opposition impacts public perceptions of other technologies. Here we present a mixed-methods study into ‘perception spillover’, examining whether the controversy over fracking for oil and gas affects public attitudes to two novel low-carbon energy technologies: deep ‘enhanced’ geothermal systems, and ‘green’ hydrogen. We argue that perception spillover is multi-faceted, and we conceptualise and test spontaneous, prompted and primed forms, examining how and why particular types occur. Using a nationally-representative UK survey and two focus groups, we show that perception spillover from fracking could lead to widespread negative perceptions of deep geothermal energy, influencing the conditions which deep geothermal would be expected to meet. Conversely, a minority of participants expressed more positive perceptions of green hydrogen because they deemed it dissimilar to fracking.Flexible fund project under the UK Unconventional Hydrocarbons project. Aims to understand the impact of fracking on public perceptions of other energy technologies

Using a combination of a nationally-representative UK survey (n=927) and two focus groups, conducted and analysed in parallel (see Methods), the goal of this research is to determine, a) whether perception spillover exists in the case of fracking in the UK, and to what extent; b) the dynamics underlying any spillover; and c) the role that technological ‘similarities’ play in any spillover effects. Survey respondents were randomly assigned to a hydrogen condition (n=464) or a geothermal condition (n=463). 86.6% had heard of fracking before, consistent with UK government statistics. Participants received information about green hydrogen or deep geothermal and were asked questions on their perceptions of the technology, before and after receiving information on fracking. Two focus groups (n=13) were conducted online in South Wales, using the same information provided in the survey. All focus group participants had heard of fracking before. All participants were recruited randomly and 'topic blind', according to demographic quotes to ensure a balance of gender, ethnicity and age. Survey participants were recruited online using Prolific. Focus group participants were recruited using Facebook adverts, although we deliberately avoided recruiting from groups with an environmental focus, and were a mix of urban (Cardiff city) and rural (Brecon Beacons).