Tokio Marine's TMGX: shared grid connections put billions of battery exposure in one place

Serguey Asael Shinder04 October 2026, 12:512 min read

Co-located solar and battery projects that share one export point are concentrating insured revenue in single locations, according to Olly Litterick, head of renewables at TMGX, the green transformation underwriting business Japan's Tokio Marine launched in 2025. Speaking to ESS News, in an interview published by pv magazine on 2 October, he said such sites now carry hundreds of millions or even billions of dollars of exposure where several insured parties share a grid connection.

Why sharing matters to an insurer. TMGX covers physical damage and the loss of revenue that follows. If a transformer or the shared export point fails, every project behind it stops earning at once, and the claims arrive together. TMGX leads on much of its book, setting terms that other insurers then follow with extra capacity, and Litterick said the task is controlling that aggregation as projects get larger almost every month. The broker Marsh, in guidance on its website, says insurers need enough separation between battery modules and site transformers and substations, and that minimising single points of failure is key to avoiding contingent business interruption losses. Some insurers, including AXIS, sell cover for lost income when the first substation a project does not own is damaged.

A young book. TMGX builds on GCube, the renewables underwriter Tokio Marine bought in 2020. Its insured participation in battery storage is about 8 GW, a figure Litterick called probably slightly outdated because the book is growing so fast. Most of it is still under construction, and utility-scale batteries have only been widespread for three to five years, so the claims record is thin. Thermal runaway remains the main driver of probable maximum loss estimates, which makes spacing between units central to underwriting. GCube reported in 2024 that more than half of battery failures happen in the first two years of operation.

The cyber gap. Standard property cover largely excludes cyberattacks; broader cyber insurance is usually bought separately in a specialist market. Project-finance lenders have traditionally required property, natural catastrophe and machinery breakdown cover. Litterick said some now insist on cyber cover too, but that it is still rare, and that TMGX is developing a broader product as demand grows.

What it means

Hybridising a grid connection is the cheapest way to add batteries, and it is what developers across Europe and the US are doing. It also turns one transformer into a shared single point of failure. As underwriters start to price that concentration, the cost of the cheapest connection rises, and spacing, redundancy and cyber cover begin to show up in financing terms rather than only in engineering reviews.