While low-level jets (LLJs) have been well characterised, their impact on offshore wind farms is not well understood. This study uses multi-elevation lidar scans to derive vertical wind profiles up to 350 m, detecting LLJs in up to 22.6 % of available measurements. Further, we analyse their effect on power conversion efficiency using operational wind farm data, observing a slightly negative influence and increased power fluctuations during LLJ events.