60 watts per 100 amp-hours @ 12 volts. Then do an energy audit for 72 hours to determine battery bank size in watt hours. Use a Kill-a-watt meter and keep the peak load below 1800 watts.
Right now I'm using 1600 watts to keep my RV at 20 C (68 f). The ambient temperature is 1 C (33.8 f). Even with a huge lithium bank it would be impossible to have enough panels to cover the load and still have the system portable.
I will limit the heated area of the RV to keep the bedroom nice and warm. The rest of the RV won't freeze up as the projected low is -5 C (23 f).
