Turbocharging is one of the modifications that causes the most insurance complications — it increases power dramatically, often in conjunction with many other supporting modifications, and forced induction is consistently flagged by insurers and industry guides as one of the highest-scrutiny modification categories.¹ Getting turbo insurance right requires declaring the full modification ecosystem, not just the turbo itself.

The Turbo Insurance Ecosystem

When you add a turbocharger, you typically also add: intercooler, upgraded fuel injectors, fuel pump, ECU tune, intake and charge piping, exhaust manifold and downpipe, potentially wastegate and BOV, and often a boosted-specific clutch or transmission upgrade. Every one of these must be declared.

Power Levels and Premium Impact

Insurers don’t publish a fixed percentage per power band — the loading depends on the specific insurer, the car, and how the build is documented. As a real published reference point, comparisons of everyday turbo variants versus their naturally-aspirated equivalents put the increase at roughly 5–15%, while genuinely high-performance turbo builds have been reported at 25–60%+ — and the highest end (heavily modified, undeclared, or combined with other performance work) can go well beyond that.¹ Treat these as illustrative bookends, not a quote: get an actual figure for your specific power level and build.

Single vs Twin Turbo Declarations

Single turbo setups are generally easier for insurers to assess — one turbo, one power figure, one intercooler. Twin turbo builds (particularly factory twin-turbo cars with upgrades) are more complex because the modification scope is larger. Both are insurable through specialist modified car insurers. Twin turbo builds benefit from more detailed documentation: dyno sheets showing power under full boost and at multiple pull points help underwriters establish a fair agreed value.

Street vs Track Turbo Builds

A street turbo build (driven daily on pump fuel) is assessed differently from a track/strip turbo build (running E85 or race fuel, slick-tyred, caged). The latter requires motorsport insurance rather than an extended road policy. Be specific about how the car is used when getting quotes — describing a heavily boosted E85 drag car as ‘a modified road car’ will produce quotes that don’t accurately reflect the cover needed.

Documentation Best Practices for Turbo Builds

• Before/after dyno sheet (same day comparison preferred)
• Boost controller calibration (target boost, overboost settings)
• Full parts list for the turbo system and supporting modifications
• Photos of engine bay showing turbo system, intercooler, and piping
• Tune sheet or map notes if available

Sources

• Alias Insurance — Are Turbo Cars More Expensive to Insure?

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