Green hydrogen has the potential to decarbonize hard-to-abate sectors and processes and should, therefore, play an important role in the energy system in achieving climate goals. However, the main hydrogen supply is still based on fossil fuels, and only limited amounts of electrolyzers have been installed. Switching from fossil-based fuel sources to green hydrogen is highly dependent on when and at what price green hydrogen will become available, which in turn is dependent on the technological development of electrolyzers. In this paper, we apply the experience curve methodology to project the capital expenditure and electrical consumption developments of the three main electrolysis technologies: alkaline, proton exchange membrane and solid oxide electrolysis. Based on our calculations, we expect that both AEL and PEM will reach similar costs by 2030 of around 300 € per kW and SOEC will remain the most expensive technology, with a considerable cost reduction down to 828 € per kW. The electrical consumptions will fall to 4.23 kWh per Nm³ for AEL, 3.86 kWh per Nm³ for PEM and 3.05 kWh per Nm³ for SOEC. Based on this technological progress, we calculate that the levelized cost of hydrogen will be reduced to 2.43–3.07 € per kg. To reach lower levelized cost of hydrogen, notable reductions in electricity (purchase) cost are required.