Green hydrogen has been touted by politicians and business leaders alike as a key fuel for a carbon-free future. But it will remain far more expensive than previously thought for decades to come, according to a new estimate from BloombergNEF.

Hydrogen companies worldwide are already struggling with canceled projects and sluggish demand. In the US, billions of dollars of projects have been stalled waiting for President Joe Biden’s administration to issue final rules for a tax credit meant to spur production.