How much solar do I need?

Could need a 100# propane cylinder (or 2) if you expect to burn propane a few days unattended.
Not sure an RV thermostat goes under 50 or 55 degrees.
Batteries can freeze if they become discharged. Especially over 50%.

assuming 50% duty cycle and 20 amps draw on the furnace fan @ 12 volts 800 watts of solar would be enough.

However it is going to require a LARGE battery bank of about 6000 watt hours (~500 amp-hours). That number does not allow for cloudy days or snow covered panels.

If you wanted 3 days of redundancy then aim for 1500 amp-hours of battery bank.

pianotuna wrote:
That number does not allow for cloudy days or snow covered panels.

..or cold batteries..?

2oldman,

Good point. I did originally design the battery bank to allow me to run a block heater for 3 hours on the battery bank at -40.

I just watched a video showing a family of 5 living in a modern house, off grid, in ID. It is heated by a wood stove so there is no furnace. Water is gravity feed from a tank up the hill. No heavy electrical load except for the washer and LP gas dryer. Their battery bank is EIGHT 6V golf cart batteries.
With 3 MASSIVE solar arrays, a 3 day early winter storm left them running off of their old 3000W generator.

eight batteries 6 volt is not much storage. I had more than that in my RV.

theoldwizard1 wrote:
It is heated by a wood stove so there is no furnace.

I wouldn't want to brave an ID winter with just that for heat.

2oldman wrote:

theoldwizard1 wrote:
It is heated by a wood stove so there is no furnace.

I wouldn't want to brave an ID winter with just that for heat.

I grew up in Vermont in a house with a wood stove for heat. ID winters are probably a wee bit more severe than VT winters, but it seems close enough to me. We did have electric heat in the house that we never used (for all practical purposes, at least). It is a comparatively large amount of work, what with stacking and fetching in the wood, and not very amenable to being left on its own for a week's vacation, but otherwise about as reliable as any heat source. It didn't seem to me like there was much bravery involved.

I was the youngest of the children, and a year before I headed off to college, my mom realized that when I was gone she would have to haul in all the wood, and got an oil fired hot water heating plant installed. (Also factoring into that decision was the fact that the stove was getting pretty well worn out and would have needed replacement before too long.)