It's inefficient but not hilariously so. Modern ICE are quite amazing technology.
Combined gas turbines (you know, the energy source that powers your electric car) are about 60% efficient for the really good ones, minus 5-7% transmission losses, minus 10-12% charging losses, minus 20% loss in cold climates, lands you at around 35-40% efficiency from fuel source to the wheel.
The Atkinson-cycle engine in the Toyota Prius gets around 40% give or take some losses in the drivetrain. Electric have plenty of upsides, but for some people with cheap gas+high electric costs+cold climate you would honestly be better driving a hybrid.