There is growing international interest in electrolytic hydrogen produced from renewable energy (often referred to as green hydrogen) as a potential zero-emission alternative to gasoline and diesel in a variety of on-road and off-road transportation applications. Currently, gasoline and diesel are priced around $4 per gallon at the pump and a gallon of either fuel is roughly the equivalent of one kilogram of hydrogen based on energy content. Although hydrogen vehicles are generally more efficient than those fueled by petroleum, transporting and dispensing hydrogen is more expensive than for conventional fuel, so hydrogen must reach a cost substantially below $4/kg, possibly as low as $2/kg, to be a cost competitive option. Is this achievable? In short, this depends on the extent to which green hydrogen markets scale up globally. Projections of future green hydrogen production costs are generally in the range of $2–$4/kg by 20301 ; however, some expect faster and deeper declines reaching as low as $1.5/kg by 20302 and even $1/kg by 2030 under ideal conditions.3 This brief examines the evidence in support of green hydrogen production achieving a cost at or below $2/kg starting from its current level of between $5 and $6/kg,4 and assesses the time point at which this cost benchmark could be achieved.