Hybrid Battery Fires vs EV Battery Fires: Is There a Real Difference?

Every few months a dramatic video of a car fire does the rounds on social media, and the caption almost always says "EV battery fire" regardless of whether the car involved was actually a full EV, a hybrid, or occasionally not even electrified at all. As an independent workshop that services both hybrids and EVs daily in Otara, we get asked constantly whether hybrid batteries are "safer" than EV batteries. The honest answer is more nuanced than either camp wants to admit.

Same chemistry, very different scale

Most hybrids and EVs sold in NZ use lithium-ion batteries (older Toyota hybrids like early Prius and Aqua models use nickel-metal hydride, which is chemically far more stable and essentially doesn't suffer thermal runaway the way lithium-ion can). The fire risk mechanism — thermal runaway, where a damaged or faulty cell heats uncontrollably and spreads to neighbouring cells — is the same physics in both vehicle types when lithium-ion chemistry is involved.

What differs enormously is scale. A typical hybrid battery pack holds roughly 1–2 kWh of energy. A full EV battery pack in something like a Hyundai Ioniq 5 or Tesla Model 3 holds 58–100 kWh. That's 30 to 60 times more stored energy in the same failure mode. A hybrid battery fire, when it happens, is a smaller, shorter-duration event. An EV battery fire involves vastly more energy that needs to burn off, which is why EV fires tend to burn longer and are harder for fire crews to fully extinguish.

What the actual data shows

Multiple international studies, including work referenced by Fire and Emergency New Zealand and Australian and European insurance bodies, consistently find that EVs and hybrids catch fire less often per vehicle than petrol or diesel cars, not more. One widely cited dataset put petrol vehicle fire rates at roughly 1,530 incidents per 100,000 vehicles sold, hybrids at around 3,475 per 100,000 (skewed by older vehicle age in the sample), and full EVs at around 25 per 100,000. The headline risk isn't frequency — it's that when a lithium-ion pack fire does happen, it burns hotter, longer, and is more resistant to being put out with standard methods.

Hybrid-specific risks worth knowing

Hybrid battery packs sit in different locations depending on the model — under the boot floor in a Prius, behind the rear seats in a Camry Hybrid, under the cabin floor in newer RAV4 Hybrid models. Because the packs are smaller, a damaged cell is more contained, and NZ workshops have successfully isolated and replaced faulty hybrid modules for as little as $600–$1,400 without incident. The bigger practical risk with older hybrids isn't fire — it's a swollen or corroded 12V/auxiliary connection causing electrical faults, which is a maintenance issue, not a battery chemistry issue.

EV-specific risks worth knowing

EV packs are physically larger and mounted low in the chassis, which protects occupants in a rollover but exposes the pack to underbody impacts — hitting a large object at speed, running over debris on a rural road, or a serious pothole strike. Physical damage to cells from impact is the leading real-world cause of EV battery fires, not spontaneous failure. This is why we recommend an underbody inspection ($90–$150) after any significant impact, even if the car seems to drive fine afterwards — a compromised cell can take hours or days to develop into a problem.

What happens if one does catch fire

This is genuinely where the two differ most in practice. A hybrid battery fire can usually be managed by NZ fire crews with standard equipment and extinguished in a broadly normal timeframe. A full EV pack fire may require significantly more water — sometimes 10,000+ litres versus a few hundred for a petrol engine fire — and crews may choose to let it burn out in a controlled way with a defensive perimeter rather than attempt rapid extinguishment, because reignition hours later is a known risk with damaged lithium-ion packs.

What NZ insurers make of it

Most mainstream NZ insurers (AA Insurance, State, Tower) don't currently charge meaningfully higher premiums for EVs specifically due to fire risk — actual claims data doesn't support it. Where premiums are higher, it's almost always driven by repair cost (EV parts and specialist labour are pricier) rather than fire statistics.

Practical steps that actually reduce your risk

Regardless of whether you drive a hybrid or a full EV, a handful of habits materially reduce fire risk in practice. Avoid cheap, uncertified aftermarket chargers and charging cables — a growing share of the fire incidents we hear about internationally trace back to poor-quality third-party charging hardware rather than the vehicle's own battery. Park undercover where practical rather than assuming it matters little; extreme heat exposure accelerates cell degradation, which in rare cases contributes to instability. And if your hybrid or EV has been submerged in floodwater, even briefly, do not attempt to start or charge it — have it assessed by a certified technician first, since saltwater or floodwater intrusion into a battery pack is one of the few scenarios that can genuinely trigger a delayed thermal event days later.

The bottom line

Neither hybrid nor EV batteries are the fire hazard the internet suggests, and both statistically catch fire less often than petrol cars. The real distinction is consequence, not probability: hybrid pack fires are smaller and more manageable, EV pack fires are rarer but more intense and resource-intensive to fight. For everyday owners, the practical takeaway is the same regardless of vehicle type — get any impact to the underbody checked promptly, don't ignore battery warning lights, and use a certified installer for any aftermarket electrical work near the high-voltage system.