In the US, the average car weight and the average EV weight are basically identical. (4300 pounds vs 4400 pounds). When you compare similarly sized models the EV tends to be about 10% heavier, but gasoline cars tend to be larger than EV's.
In the EU an average car is 1400 kg (3000 lbs), with most vehicles probably in the 1000-1200 kg range. We don't really want the average here, but the median - and we don't want to compare to the average EV, but to the equivalent EV - comparing an F150 to, say, a model 3 isn't right.
A BYD Dolphin, roughly sized like a VW Polo, is some 400kg heavier than the polo. A Polestar 2 is roughly 500 kg heavier than equivalent sized cars. In other words, something like 33% heavier.
FWIW I learned semi recently that cars get heavier and heavier because it improves their “ecology” rating… the ratings consider that moving 50% more weight with only 33% more gas is better than moving 0% extra weight with 0% more gas. And so a heavier car that uses a little more gas gets a better energy rating.
It’s moronic. But that’s how it works and why cars are getting bigger and bigger.
The VW Golf Mk8 might be a better comparison with an unloaded curb weight of 1255 kg, which reduces the gap from 543kg to 403kg.
(Note that for the gasoline and diesel cars, lighter trims give longer range, whereas it is opposite for electric cars, and that a fully loaded 45L tank of a polo weighs less than 40kg, especially if gasoline)
The lower battery trim is not available in all markets, and only does 300km on a charge which is below average. As such the minimum weight will have to be the 1658 kg value.
The BYD is taller to offset the battery, making the size misleading. However, the golf is not particularly a particularly good or space efficient car - others will do better at similar or lower weight.
250kg seems like a fair minimum weight increase, roughly 20%. The larger the car, the larger the gap though, as the rocket equation catches up - see a Skoda Octavia vs. a Polestar 2.
EVs are still way more efficient, but that doesn't mean we should turn our blind eye to making an already bad tire problem worse.
Same tier EVs are always more powerful than gasoline cars as they are generally just battery limited, not motor limited.
EVs are just a better tech in that regard, and buyers are not buying a Dolphin or golf based on torque or max HP. They're compacts in the same space. Someone looking at a dolphin would more likely be looking at the lighter eco motors.
This is true in other tiers too, e.g. a performance tier gasoline car might be 250-350 HP, while the same tier EV might start at 450-550hp just because they can.
The difference within a tier, simply based on the fact you're replacing at best a lightweight 100kg engine with 400-500kg worth of battery, can't be as small as you suggest.
With larger EVs, the battery weight is much greater, increasing the impact. Rocket equation and all.
