Consumer Watchdog released a report on Thursday, saying that Californians spent $1 billion more on gas than the rest of the country during the month of March. 

The group says the price spike is due to a shortage of gas caused by two refineries going offline. One caused by a labor strike at Tesoro's Martinez, a California refinery, and the other by the explosion at the Exxon Mobil refinery in Torrance in February. 

"When something breaks, when refineries go down, prices go way up and that's pure profit for the oil companies involved," said Consumer Watchdog President Jamie Court. 

However, one expert thinks that Consumer Watchdog is misinterpreting the data. 

"Consumer Watchdog is not a credible source on this issue," said Tupper Hull of the Western States Petroleum Association. 

He says they're looking at data from different sources and trying to compare them. 

"They're comparing apples to oranges," said Hull. 

In fact, Hull says this is something that happens on a regular basis in California because "our markets here are somewhat isolated [from] other sources of supply." 

Consumer Watchdog representatives attended a Senate hearing regarding the sharp increase in gas prices and is pushing to keep gas prices low for drivers across the state.