Shipping has a habit it can’t seem to shake off: the tendency to buy an energy efficiency technology (EET) based on headline savings results. These figures are based on performance achieved on another vessel under controlled conditions that are unlikely to reflect the buyer’s own operating profile, vessel characteristics or real-world conditions. For air lubrication systems (ALS) performance figures are often taken from sea trials held in light or ballast conditions, where compressors face less hydrostatic pressure to work against, so the system typically performs at its best. The data being used to sell these systems are not wrong, but they don’t tell a ship owner the full story. Research from the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping regarding the ship owners and charterers’ experience using compressor-driven ALS in commercial operation shows net savings spanning a range from zero to six percent, varying with draught, hull form, speed and sea state. The problem is not with the technology itself but that these numbers differ quite significantly from the data being marketed to the industry. That selective use of performance data has contributed to a credibility gap in the EET market. As a result, some shipowners are delaying investment decisions until a stronger body of independently validated evidence becomes available. That is a worrying outcome for decarbonisation, and a disappointing outcome for the suppliers who have invested in real engineering and a bespoke, vessel-specific measurement and evaluation approach. These suppliers are being asked to compete in a market that is only reading headline figures. The data ship owners should be asking for is what a supplier predicts their system will deliver on their vessel, at their draughts, across the speeds and routes they actually operate. Framing clean technology investment around that question, before capital is committed, is the most direct lever ship owners have to raise the standard of tr