Have posted elsewhere. We have 1.4 kW of solar and 9.7 kW hours of LFP batteries. The heater takes about 8 to 10 amps at 12 V and the 9.7 kW hours is the same as 760 amp hours at 12 V but we can utilize 90 of that power storage. If the heater runs 24 hours a day, that is 240 amp hours which is nothing for the battery suite. If we have sun, things go well. We had 6¨ of snow at Bosque del Apache and I didn not get on roof for 3 days but we still had 50% of power storage.
The battery suite is at 54 V and weighs 160 pounds.
We do use am Olympian Wave 8 which puts out 8000 BTU or 2.5 kW. Works great but at temperatures below zero, the sewer outlets freeze. It got down to minus 5 F just before we flew down to Guatemala for 9 to 11 weeks, and this is where we are now.
The Olympian Wave 8 is sufficient to keep the 34 5th wheel in the 60s at sub freezing temperatures.