The Eaton fire, which killed 19 people and destroyed or damaged more than 9,000 homes and businesses in the Altadena area in January 2025, was caused by electrical arcing on an out-of-service Southern California Edison transmission tower, according to investigative reports released by the Los Angeles County Fire Department on August 4, 2026. The investigation was conducted jointly with CAL FIRE over 18 months, with retained electrical and metallurgical experts.
The reports found that the fire originated in dry vegetation below SCE transmission towers on a spur ridge above Eaton Wash. Accounts of the reports by the Los Angeles Times and AP identified the idle Mesa-Sylmar line as the source. According to a summary of the findings, arcing at a conductor ejected hot metal particles into the dry fuel bed below, and ignition followed within seconds.
"While the cause has been determined, our focus remains on assisting our residents to rebuild their homes and livelihoods, and ensuring lessons learned drive meaningful and impactful change in memory of the 19 lives lost," said Fire Chief Anthony C. Marrone.
The county said the reports were redacted because the Los Angeles County District Attorney's Office is conducting an ongoing review of the evidence.
Background
The Eaton fire started on the evening of January 7, 2025, during an extreme Santa Ana wind event. It burned alongside the Palisades fire, and together the two fires were among the most destructive in California history. Swiss Re Institute estimated insured losses from the Los Angeles wildfires at about $40 billion, the largest insured loss event of 2025.
Speculation focused on SCE equipment soon after the fire. The idle line had not carried power for decades but remained in place. One theory raised in litigation was that energized lines nearby could have induced current in the idle conductors. The US Department of Justice sued SCE in September 2025, seeking to recover federal costs related to the Eaton fire and an earlier fire. Thousands of property owners, insurers and public agencies have also sued the utility.
Utility liability in California
Under California's doctrine of inverse condemnation, a utility can be held liable for property damage caused by its equipment even if it was not negligent. That doctrine has exposed California's investor-owned utilities to enormous wildfire liabilities. PG&E filed for bankruptcy in 2019 after its equipment caused the 2018 Camp fire.
In response, California created a wildfire fund in 2019, financed by utility shareholders and customers, to pay eligible claims above a threshold and protect utilities from insolvency. The fund was established with about $21 billion. In September 2025, Governor Gavin Newsom signed SB 254, which extended the fund with an additional $18 billion, split between ratepayers and shareholders. SCE has said it expects the fund to cover much of its liability from the Eaton fire if it is found responsible, subject to reimbursement rules that depend on whether the utility acted prudently.
Implications for SCE and investors
The cause finding is a key step in determining SCE's liability, though it does not by itself settle questions of negligence or the prudence review that determines how much SCE must reimburse the fund. SCE and its parent, Edison International, have previously set up a compensation program for Eaton fire victims to resolve claims outside court. Credit rating agencies and investors have been watching the case closely because of its potential size.
The finding that the fire started on idle equipment raises questions about utility practices for decommissioning and maintaining unused lines. Many utilities have idle lines left in place, sometimes for future use. Regulators may require utilities to inventory and either remove or properly de-energize and ground such infrastructure.
Idle lines across the industry
Idle transmission lines are not unusual. Utilities sometimes de-energize lines that are no longer needed but leave towers and conductors in place, either because removal is expensive or because the corridor may be useful later. In wildfire-prone areas, such infrastructure still has to be inspected and maintained, because conductors can move in high winds and contact other equipment, and because nearby energized lines can induce voltage in idle conductors if they are not properly grounded. Utility regulators in several western states are expected to review practices for idle facilities in light of the findings.
Wildfire risk and climate
Wildfire risk in California and across the western United States has grown with hotter temperatures, longer dry seasons and the expansion of homes into fire-prone areas. The January 2025 fires followed two wet winters that produced abundant vegetation, then an exceptionally dry autumn and winter that left it parched. Scientists have linked such swings between wet and dry conditions to climate change.
Utilities have responded with large wildfire mitigation programs, including undergrounding lines in high-risk areas, installing covered conductors, increasing vegetation management and using public safety power shutoffs, which cut power to lines during dangerous weather. These programs are expensive and are paid for largely by customers, which contributes to California's high electricity rates.
Wider energy sector effects
Wildfire liability has become a national issue for utilities. Xcel Energy agreed to a settlement over the 2021 Marshall fire in Colorado, and utilities in Oregon, Hawaii and Texas have faced large claims. Some states have enacted laws to limit utility liability if utilities follow approved wildfire mitigation plans. Insurance for utilities in fire-prone areas has become harder to obtain and more expensive.
For energy markets, wildfire risk affects utility credit ratings, cost of capital and the ability to finance grid investment needed for growing demand, including from data centers and electrification.
Rebuilding and the grid
Rebuilding Altadena and the Palisades also involves decisions about the electric grid. SCE and the Los Angeles Department of Water and Power have discussed undergrounding distribution lines in burned areas as part of reconstruction. Undergrounding sharply reduces ignition risk but costs several times more than overhead lines, and the question of who pays is part of the wider debate about affordability in California.
What to watch
Key items include the District Attorney's review, SCE's response to the findings, the progress of litigation and settlements, claims on the wildfire fund and any regulatory action on idle infrastructure. The California Public Utilities Commission's prudence review will determine how much of the cost falls on SCE shareholders.