Kingstone adopts ZestyAI wildfire model for California

Kingstone has selected ZestyAI's Z-FIRE model as it enters the California homeowners market on an excess and surplus lines basis.

The insurer plans to use the wildfire risk model in rating and underwriting as it expands beyond its core Northeastern markets. It said the California launch follows the same underwriting approach used in New York, where it recently reported strong financial results.

Z-FIRE is designed to assess wildfire exposure at the individual property level rather than across broad territories. The model evaluates factors including defensible space, building materials, topography, and vegetation, allowing insurers to distinguish between homes in the same postcode or rating area that face different levels of wildfire risk.

That level of detail matters in California, where insurers have been reassessing wildfire exposure and access to cover has become a growing issue in some areas. Kingstone will use the model as one tool within its underwriting framework for catastrophe-exposed regions.

California push

The move marks Kingstone's first expansion outside the Northeast. California is part of a broader growth strategy, with initial business to be written on an excess and surplus lines basis, giving insurers more flexibility on pricing and policy terms than the admitted market.

Its California structure will allow it to use forward-looking wildfire models, set rates to meet margin requirements, and apply strict underwriting standards, including real-time accumulation management. Kingstone is also maintaining a 30% quota share on its California business during the initial scaling period to manage net exposure.

Sarah Chen, Senior Vice President, Chief Actuary and Head of Product Management at Kingstone, described the move as an extension of the company's existing underwriting discipline.

"Our California entry reflects the same disciplined, data-driven approach that has driven our results in New York," said Sarah (Minlei) Chen, Senior Vice President, Chief Actuary and Head of Product Management, Kingstone. "ZestyAI's Z-FIRE model complements our Select platform by providing the property-level wildfire intelligence we need to rate and underwrite with precision in a complex and dynamic market like California."

Model approval

ZestyAI said Z-FIRE was the first AI-based wildfire model approved as part of a carrier rate filing in California. It added that the model is approved across Western wildfire states and that its wider portfolio has received more than 200 regulatory approvals across the US.

The approval record is notable because regulators have closely scrutinised insurers' use of advanced models in pricing and underwriting, particularly in areas exposed to climate-related risks. In California, where traditional insurers have pulled back from some wildfire-prone locations, property-level models have drawn attention from insurers seeking to keep writing business while managing loss exposure more tightly.

ZestyAI Founder and Chief Executive Officer Attila Toth said the insurance market was changing as carriers adapted to wildfire risk.

"Wildfire risk is pushing the insurance industry to embrace more advanced analytics and AI-driven decision making," Toth said. "With a clearer understanding of risk, insurers can make confident decisions about where they grow, how they manage exposure, and how they continue serving communities in wildfire-prone regions."

Kingstone is a property and casualty insurance holding company focused on the Northeast through its main operating subsidiary, Kingstone Insurance Company. It was the 12th-largest writer of homeowners insurance in New York in 2024 and is also licensed in New Jersey, Rhode Island, Massachusetts, Connecticut, Pennsylvania, New Hampshire, and Maine.

The California launch places the insurer in one of the most closely watched homeowners insurance markets in the US, where carriers, reinsurers, and regulators are all grappling with how to price and manage wildfire exposure amid rising catastrophe risk.