You’ll hear folks say that battery electric vehicles (BEVs) are more prone to catching fire than internal combustion engine vehicles (ICEV), or that EV fires are inherently more dangerous than fires involving gas or diesel vehicles. The media often runs stories about EV fires. But are these anecdotes representative of the true risks? I tell people that if we want to understand an issue, we need to know the scale, rate, and trend based on quantitative data. Fortunately, researchers are exploring questions about the fire risks for different types of drivetrains, comparing internal combustion vehicles with hybrids and battery electric vehicles. The results might surprise you.
Which types of vehicles are most likely to be involved in a fire?
The National Transportation Safety Board addressed this question in a comprehensive study. When the NTSB evaluated the incidence of vehicle fires and normalized the results per 100,000 vehicles to account for the different number of vehicles on the road, they found that EVs are the least likely to be involved in vehicle fires:
- Battery electric vehicles: 25 fires per 100,000 vehicles
- Gasoline ICE vehicles: 1,530 fires per 100,000 vehicles
- Hybrid electric vehicles (HEV/PHEV): 3,475 fires per 100,000 vehicles
Hybrid vehicles are more complex than either battery electric vehicles or gasoline powered cars. They carry both of these drivetrains and because the technology has been around longer than BEV, there tends to be more of them on the road of older age. These are all factors that could contribute to the greater incidence of vehicle fires as suggested by Motor.
Are battery fires inherently more dangerous than gasoline fires?
One of the most respected names in product safety, the Underwriters Laboratory (UL) Research Institutes, addressed this question with the most comprehensive study of EV fires to date. They conducted a series of carefully designed experiments to tease out the dangers associated with EV fires relative to other drivetrains. Their results are nuanced, and provide important guidance for emergency services to address fire safety when vehicles do catch fire. They conducted their experiments with fully charged BEVs, which provide an upper limit on the potential problems associated with BEV fires since not all real fires will involve fully charged BEVs. They summarized their results in four key findings. I provide some key quotes from the UR report below.
“The data resulting from the free burn experiments demonstrated that fire dynamics and associated chemical hazard in both EVs and ICEVs are primarily driven by the fire in the passenger compartment materials, and thus were similar between powertrain types.” They go on to state: “The time to burnout, peak heat release rate, and total energy release were similar between EVs and ICEVs. EV fires did show a greater variability in fire growth rate, exhibiting both faster and slower growth rates than their combustion engine counterparts.” They conclude: “Though anecdotally there have been concerns about major differences in EV fire behavior, no evidence was found that EVs burn hotter, or last longer than their conventional counterparts.”
Overall, this careful scientific study concluded that while there are at present, greater chemical risks associated with some BEV fires, that overall they behaved similar to ICEV fires and could be extinguished safely with proper use of existing firefighting equipment.