Drivers of fuel-cell cars in California had already been reeling from the news that most hydrogen filling stations had ramped up their price pump to $36/kg, pushing up the cost of filling a Toyota Mirai to around $180.

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But at the time of publication, 21 of the state’s 53 filling stations are offline — with most of the temporary closures due to “disruption” in the supply of gaseous hydrogen in Southern California.

A total of 15 of the 29 refuelling stations in the sprawling Los Angeles metropolitan area are offline, as well as both of the options in the San Diego area — leaving drivers in the state’s southernmost big city unable to refuel.

Almost all of the stations that are still open in Southern California are supplied with liquid hydrogen, rather than the gaseous type.

According to the California-based Hydrogen Fuel Cell Partnership (H2FCP) website, only 11 of the offline stations are due to the disruption. Seven are down because of maintenance or technical issues, with no explanations for the others.

In a note to users this week, H2FCP wrote: “A large number of Southern California Hydrogen stations are not available due to a disruption in the availability of gaseous hydrogen.

“Hydrogen stations that have alternate supply chain continue to be available, noting that these stations will experience higher than normal demand. Time of disruption resolution is not known. We will post additional information as we receive it.”

And last week, True Zero, which operates 37 of the 53 hydrogen filling stations, wrote a letter to drivers, saying: “We regret to inform you that our supplier of gaseous hydrogen for our Southern California stations experienced a major service disruption, which has stopped our supply of gaseous hydrogen. We do not have an estimated date for when hydrogen supply for these stations will resume.”

It then lists ten of its facilities that it expects to “experience fuel shortages”, saying that the others in Southern California will not be affected.

“We apologize for this inconvenience and are working hard to restore our hydrogen supply as quickly as possible.”

California is the only US state with public hydrogen refuelling, and therefore the only current market for fuel-cell cars.

According to H2FCP, 17,284 hydrogen cars have been sold or leased in the state to date.

Hydrogen Insight calculated last week that it is now almost 14 times more expensive to drive a Toyota Mirai (by far the most popular model in California) than a comparable Tesla Model 3, due to the recent price rise.