The transitions literature has framed energy transitions as a process involving material and social consequences. Such radical changes can also be viewed as constituting discursive dimensions, involving debate, idea exchange and value positioning. The implementation of a biomass energy system in residential buildings in a socioeconomically deprived community near Liverpool, UK, is investigated for its acceptance by, and impacts on, the community. A mixed-methods approach involving questionnaire, focus group and interview data reveal how practical, on-the-ground energy transitions are understood at the community level. Given the changes to how residents pay for their energy in the study community, from prepayment meters to pay-as-you-use methods, considerations of 'efficiency' are debated and framed on the cost of energy rather than from an environmental performance perspective. Although the intention of low-carbon energy transitions in low-income communities is to deliver economic and environmental benefits, many unintended social consequences arose from top-down decision-making choices and implementation mechanisms. These processes exacerbate economic inequalities and inequities. Justice implications arising from this study have clear repercussions for future implementation of similar, and additional, sustainability interventions that attempt to address climate change in the built environment. Practice relevance The successful implementation of a decentralised energy system requires more than a technological approach. This case study emphasises the need for extensive community engagement when undertaking local energy transitions. In particular, attention needs to be given to how vulnerable people are affected by pricing and given clear information on how to use the new system. Policy recommendations include: the choice of energy technologies should not disrupt vulnerable residents' daily routines and ability to pay; the provision of substantial pre-, during and post-installation community engagement is needed to improve familiarity with new energy systems; and adequate opportunities for listening and responding to residents' concerns prior, during, and after the installation of low-carbon energy systems.