Here in Norway we have 20% of private cars electrified. No impact on the grid and not a lot on total electricity use. If all energy used in the transport sector were to switch to electricity today it would add about 50% to the demand for electricity. But EVs are about 90% efficient versus about 25% or less for ICE vehicles so in fact it would add less than 15% to the electricity demand.

https://publikasjoner.nve.no/rapport/2023/rapport2023_35.pdf