Fehlhafer, if you read the post, the OP doesn't have electric hookups.
Big2na, the heat source in RVs, is called a furnace. saying heater confuses people who think you have an electric heater.
i see this is your first post, have you read up on how to keep hybrids warm or cool? having 3 tent ends will be hard for a furnace to keep up with if you don't research on how to keep hybrids warm in cold weather.
remember, manufacturers don't recommend hybrids for very cold weather, since they have big holes in them.
using PUGs or solar blankets on top of the canvas ends and Reflectix in the windows or sides, will greatly help the canvas ends retain heat.
we stayed in Yosemite in snow, with low temps and had no electric.
by using PUGs and Reflectix, we kept it very cozy inside.
now, some have done mods to add vents or re-route vents to help direct the heat to the colder areas.
by the way, sounds like you're talking about Calif. state parks, since ours have virtually none with any kind of hookups.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC