Theory to Practice: Propane Consumption for Long term 5th Wheel Living during SHTF.

I didn't know to which forum this post was best suited, but here it is.

We recently decided to demolish our cabin and bought a 5th wheel camper to park on the site while we rebuild. This could take 5 years or more, depending on budget and how much time we devote to it.

There's currently fairly reliable power and a new well on the site with an off grid, slow start 110V well pump.

We primarily plan to bug in, but this cabin is our secondary option with ~ 1 month of long term food stored there. Much more could be brought from our main house if needed.

I also have a 3000 watt inverter generator on site. It is converted to also burn propane.

The camper has 2 x 100 watt solar panels mounted on the roof and I have 2 x 100 amp hour deep cycle batteries. Flooded lead acid type, so only 100 amp hours of total capacity without significantly reducing the number of battery charge/discharge cycles.

The camper is a 4 season model, with better than average insulation, heat ducts in the basement, and electric heating elements beneath the tanks.

Electricity, food and water are covered.

I am focused on how much propane I need to have on hand.

Here are some assumptions that I am using in my calculations:

1. A gallon of propane contains 90,000 BTU. I know that in reality it is slightly more but I am using the more conservative number as a built in "fudge factor".
2. Without the generator or shore power, the fridge will use .25 gallons per day, or about 5 gallons per month if you rounded up.
3. Cooking will consume another 5 gallons per month, assuming 15,000 btu per day usage, which is about an hour per day with two burners.
4. The 60,000 BTU tankless hot water heater is a large load. Assuming 10 minutes worth of hot water per day, that will be another 5 gallons per month on the high side.
5. The largest two loads will the generator and the furnace. In the heat of summer, the generator will consume about 2 gallons every 5 hours at half load. A 30,000 BTU furnace will burn about 1/3 gallon per hour. Or about 2 gallons per day assuming a 3:1 duty cycle (ie. runs for 6 hours intermittently per day). Essentially, either will consume 60 gallons per month. In theory, I shouldn't need to use both of them simultaneously for long periods of time due to seasonal differences in the nature of the loads.

When it is all said and done, I will need about 75-80 gallons on hand for each month that I stay there should TSHTF. This should be a reasonably comfortable lifestyle.

Of course, using the AC (and therefore the generator) less would help immensely as would bundling up during the colder months. But I can't compromise so much on the heat during the winter because of concerns that the fresh water tank and plumbing would freeze. Also, some generator usage would be required because a series of overcast days would not allow the batteries to be fully charged by the panels.

Adding more solar could offset some of the electrical loads, but there's more than enough capacity to cover the LED lighting and refer control circuitry for a week or more and at least one, possibly two, overnight uses of the furnace fans. It would take a crap ton more money to upgrade panel and battery capacity to reach the point that I can power the air conditioner and any other AC loads solely by using an inverter and batteries. The cost of 4 LiIon 100 ah batteries alone is more expensive than buying a new 1,000 gallon propane tank and having it delivered, set up and filled.

As it stands, I have about 100 gallons of propane stockpiled there already in various containers. I would like to double that over the next year.

I like thought experiments like these.

Under similar circumstances, how long do you think you could stretch out that much fuel and how did you arrive at that conclusion?

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Theory to Practice: Propane Consumption for Long term 5th Wheel Living during SHTF.