Utility giants PG&E Corp. and Edison International could gain at least some protection against future wildfire damages under a bill that’s advancing in California’s legislature.

An amended bill being weighed by California’s Senate would shield utilities that follow approved safety plans in future state proceedings should one of their power lines spark a wildfire. Utilities would remain vulnerable to potential civil lawsuits, and the legislation wouldn’t be retroactive — meaning PG&E and Edison could still face billions of dollars in costs from wildfires that destroyed thousands of structures last year.

Both PG&E and Edison rallied on news of the amended bill Tuesday as it offers investors some clarity as to how California’s utilities will be held responsible for wildfires that have intensified amid warmer temperatures and drier weather. Analysts have estimated that blazes that broke out last year alone could cost PG&E more than $15 billion in claims and Southern California Edison more than $4 billion.

The scale of the destruction by the fires and the uncertainty around whether the utilities will be stuck with the bill have wiped out billions of dollars of market value from both companies.

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