With any petrol( including hybrid )car when towing caravan you can double the fuel consumption.
That's not a bad worst-case assumption, whatever fuel type your car is.
Your outfit is likely to be about double the weight of your car alone, and double the wind resistance. In which case, the amount of energy or fuel it takes to move the whole thing (at the same speeds and accelerations) will also be double. Doesn't matter whether it's petrol, diesel or electricity.
Then some things will make the impact of towing on fuel consumption not quite so severe.
You probably drive slower, with slower acceleration.
You might have an unaerodynamic SUV, so adding the caravan on the back doesn't make the wind resistance so much worse.
Your towing vehicle might be much heavier than the caravan, so actually the weight of the outfit isn't doubled.
Whatever the specifics of your outfit, it's still quite a shock the first time you figure out how much more fuel you're using!