"We are surprised just because it was unexpected, given that prices have typically dropped," said Devin Gladden, spokesman for AAA. "It just speaks to the unparalleled nature of how many refineries were down and how tight the supply was that ultimately gave rise to the price increase."
Most refineries perform scheduled maintenance in the fall or winter, which usually does not affect gasoline prices because refineries can work around the repairs. They may want to buy gasoline ahead of knowing that their facilities will produce less of it, for example.
However, over the past two weeks, several refineries have been supplying the West Coast with gasoline unexpected power outages at the same time, further hampering California's ability to produce fuel.
At most, seven of the region's 25 refineries were either down or to a lower production capacity, Gladden said.
"To see multiple refineries have unexpected power outages at the same time, is not normal," said Patrick DeHaan, head of petroleum analysis at Gas Buddy.
More than other states, California gas prices can sometimes skyrocket, because the state mandates cleaner gas with fewer emissions. This means that California gas costs more to refine, because it is a special oxygen-rich blend that meets the state's strict air quality rules. Refineries must use a specialized process, and only a few refineries are capable of producing approved gas in California, making it more difficult for the state to import oil.
However, price increases are slowing as refineries work to resume production capacity. Provided there are no further power outages, DeHaan expects California pump prices to stabilize toward the end of the week.