We dry camp in the winter every year in our RV. AS discussed, most heating systems require too much power to run without generators, are noisy, etc. We faced the same problems even with our 600w solar and 8 6v battery system.
Our solution is a "Blue Flame" heater. These require no power to operate, are basically silent, look nice with the visible flame, inexpensive, easy to install, are fuel efficient, and most important, heat very well and fast!
Yes, they do produce condensation and Co2, but both can easily be dealt with. Co2 is deadly, but can be handled safely. I use 2 Co2 monitors, leave 2 vent sources open - high and low, plus the unit has Co2 monitor and automatic shut down. But the best way to deal with Co2, and what we do, is not sleep with the heater running!
Condensation is minimized by the same vents as the Co2, and has never been a problem.
This heater heats or RV - 340sf, to very comfortable temp in just a few minutes, has a great ambiance with the visible flame, and when not needed, we store it under the bed.
Just another option.