The weight of a plug-in hybrid electric vehicle (PHEV) negatively affects its acceleration performance in electric vehicle (EV) mode. Because PHEVs generally weigh more than their conventional or hybrid counterparts due to the larger battery packs and additional components, this extra mass results in slower acceleration when operating solely on electric power.
How Weight Affects Acceleration in EV Mode for PHEVs
- Heavier weight leads to slower EV acceleration: Tests show that PHEVs can take roughly twice as long to reach 60 mph in EV mode compared to hybrid mode, largely because the electric motor alone has to propel the heavier vehicle without assistance from the gasoline engine. For example, the Toyota Prius Prime and BMW X5 PHEVs showed significant slower times to 60 mph in EV mode.
- High curb weight vs. electric motor power: The Kia Sorento PHEV weighs over 4,500 lbs but its electric motor only produces about 90 horsepower, which is adequate but not powerful enough to swiftly accelerate such a heavy vehicle. Increased weight makes faster acceleration difficult because the electric motor has to work harder to move the mass.
- Acceleration time examples: The Mercedes-Benz GLE450e PHEV weighs about 5,940 pounds and while it reaches 60 mph in 5.3 seconds with the hybrid system, it takes 14.4 seconds in EV mode alone, almost three times longer. This slow EV-only time is mainly attributable to the combination of vehicle mass and limited electric motor output relative to the vehicle’s weight.
- Additional weight affects range more than acceleration directly: Additional passengers or cargo add weight and can influence acceleration, but their impact on EV range may be more noticeable than on short-term acceleration. Still, the base heavy weight of PHEVs inherently limits acceleration speed in EV mode.
Summary
The extra weight of plug-in hybrids (due to batteries and components) makes them slower in EV mode compared to hybrid or gasoline modes because the electric motor must move a heavier vehicle. This results in longer acceleration times to highway speeds, often twice or more as long as in hybrid mode. The relationship between weight and acceleration is direct: more weight requires more power to accelerate quickly, but electric motors in many PHEVs are sized more for efficiency and adequate performance than rapid acceleration by themselves.
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