Acceptance before deployment: a systematic review and measurement audit of public acceptance research on four emerging net-zero energy technologies

Deep decarbonisation increasingly depends on technologies that most citizens have never encountered: small modular reactors (SMRs), hydrogen energy systems, carbon capture, utilisation and storage (CCUS), and offshore wind. Public acceptance is widely treated as a make-or-break condition for deployment, yet the evidence has grown in technology-specific silos and has never been audited for how acceptance itself is measured. This PRISMA 2020 systematic review spans all four families. A frozen, benchmark-validated search of Scopus and OpenAlex (16,806 unique records) was screened with a calibrated human–machine workflow (kappa = 0.821; 100% benchmark recall), yielding 689 full-text candidates and 534 included primary studies. Three findings stand out. First, the field is expanding rapidly and asymmetrically: 57% of the evidence post-dates the most recent comprehensive review, with CCUS (217 studies) and hydrogen (186) dominating, offshore wind (136) consolidating, and SMRs (17) markedly under-studied relative to policy salience. Second, study-level associations are directionally consistent for perceived benefit (70% positive), trust (58% positive) and perceived risk (54% negative), but inconsistent for proximity and socio-demographics, challenging distance-based siting heuristics. Third — the central result — the measurement base is thin: only 1.5% of studies reused a pre-validated acceptance instrument, 71.3% relied on ad hoc measures, 82.8% were one-shot cross-sections, 35.2% did not measure familiarity, and 72.7% examined pre-deployment technologies. Much of the literature thus appears to record unstable constructions of unfamiliar objects rather than settled public judgements. A measurement-first agenda — shared instrument cores, mandatory familiarity assessment, deployment-stage-explicit reporting, and longitudinal designs — is proposed.