canoe, that's true in very cold weather (under 20 degrees). But we boondock all the time in night-time temps in the mid-20s. We only run the furnace during shower time, a few minutes a day. Otherwise, we dress like Eskimos, no problem. And our 120 watt solar panel recharges the batteries every day.
Obviously, that's not going to work in cloudy weather! But in the eastern Sierra, it's sunny most of the time, even during the winter months.
So it really is possible to dry camp or boondock in the winter, if conditions are right.