Pacific Gas and Electric Corporation (PG&E) said the fires, which devastated huge areas of California, had triggered "significant" potential liabilities.
Reports say the company could face costs of up to $30bn (£23bn).
In November, the most deadly fire in Californian history began in the town of Paradise, killing 86 people.
PG&E, which serves 15 million Californians - almost 40% of the population of the state - warned then it could face "significant liability" beyond its insured amount if its equipment was found to have caused the fire.
