AL - You can go all (120/240 VAC) electric if you use an inverter to power those
circuits you want to use when you are not connected to land power. No more battery
problems except for the breakaway battery.
If one side of the 50 amp plug is used for any 120 V heating and the other side is used
for everyting else, lights, radio, etc., you can stay in 30 amp (120 VAC) park sites
with most of your electric equipment working (30a/50a adapter). If you have 240 V water
heater, A/C, heat pump or furnace, it will not work on a 30 amp supply. An electric
range is 120/240 V on the surface units so they will heat up low.
The 50a/30a adapter is simply blank on one of the 50a prongs - not connected to
anything. A 30a/50a adapter may be harder to find than a 50a/30a but they are available,
or you can make one up or have it made up.
We have a 120 V heat pump. Unfortunately it's an Instamatic, which has been gone for 20
years. There may be others. A heat pump draws less than 1/2 as much current per Btu as
a resistance heater like the heat strips common in A/C units, but heat pumps work only
above around 36 degrees F. Modern ones are more efficient than old ones like ours, so
you can get quite a lot of heat on a 30 amp circuit.