The reality is that particularly in winter and outside, most recent EV cars will barely gain any charge from a 120V standard power outlet - keeping the battery conditioned eats up all of that power.
That hasn't been my experience charging outside in the northwest with average winter temperatures.
But the charger does power a heater to keep the batteries around freezing, so you're right, it's better to charge in a garage. And cold weather causes additional losses, but I would expect no more than 20% or so. I lose 10% range just by running the dashboard heater.
