Abstract Purpose Transformers are indispensable for bulk power transfer and safe distribution, operating for decades and representing major capital outlays. Recent surges in material prices, ageing fleets and stricter EU efficiency rules compel operators to plan replacements years ahead and weigh competing designs. Although life‑cycle assessment (LCA) could steer these choices, it remains little used in the sector. By reviewing fifteen transformer LCAs (2007–2026), we propose a methodological roadmap that supports decision‑ready analyses and comparative studies. Methods The reviewed transformer LCAs were benchmarked against ISO 14,040/44. For each study we examined: goal and scope definition, including functional‑unit choice and boundary completeness; life‑cycle inventory practice; impact‑assessment method and category set; quantification of operational losses, recycling and end‑of‑life; sensitivity and uncertainty analysis; linkage to eco‑design or cost optimization; and transparency of interpretation and reporting. Recurring strengths, omissions and inconsistencies were synthesized into guidance that addresses functional‑unit alignment, data‑quality documentation, allocation and cut‑off rules, loss modeling, and the need for critical review. Results and discussion Across the reviewed studies, goals are often vague and functional units inconsistent (e.g., kg CO₂-eq/MVA vs. kg CO₂-eq/MWh, among others), undermining comparability and sometimes biasing results. Data gathering is hampered by the many actors spanning extraction, manufacture, long operation, and disposal, yet data-quality descriptors are seldom provided. System boundaries differ, with cut-off criteria and allocation rules rarely justified; capital equipment and shared utilities are not explicitly allocated, and end-of-life is often deferred. Sensitivity analysis appears in just nine papers and full uncertainty propagation in only two. This methodological dispersion limits the usefulness of current transformer LCAs for planners, designers, and regulators. Among the studies that include the use phase, several report that operational no-load and load losses contribute about 90–99% of total life-cycle impacts, while manufacturing, transport, and disposal are generally secondary contributors. Conclusions and recommendations Operational no‑load and load losses remain the dominant environmental hotspot, so loss‑reduction technologies are the foremost mitigation lever. However, many current transformer LCAs are hampered by vague functional units, truncated system boundaries, minimal sensitivity testing and the lack of ISO‑required critical review. Progress hinges on richer public databases, fully harmonized cradle‑to‑grave scopes, voltage‑appropriate functional units, dynamic loss modeling that reflects evolving grid mixes, transparent allocation of shared utilities and capital equipment, clear data‑quality criteria and routine uncertainty propagation. Implementing these improvements will turn transformer LCAs into reliable tools for eco‑design, procurement and carbon‑policy decisions.
Oria et al. (Mon,) studied this question.