A typical 12 cubic foot propane refrigerator consumes an average 1.5 lbs. of propane per day, which works out to about 1,400 British thermal units of energy per hour or 32,225 BTU per day. Propane refrigerators are available as small as 4 cubic feet and as large as 18 cubic feet. Small units may consume well under 1 lb. of propane per day while large units may consume nearly 2 lbs. per day. Consumption also varies somewhat by brand.
A standard 20 lb. propane bottle, widely available, provides 430,000 BTU of energy when full. At 32,225 BTU or 1.5 lbs. per day, that 20 lb. bottle will run your 12 cu. ft. propane refrigerator for 13 days. If you used two of these bottles, you would get around 26 days of running time. If you had access to larger propane bottles, you could run your typical 12 cu. ft. refrigerator far longer. A pair of 40 lb propane bottles would run your unit for 52 days, while a single 100 lb. bottle would run the appliance for 66 days.
Refrigerators running on propane or other fuels were introduced in the 1930s, when most of rural America lacked any electric service. Fuel-powered refrigerators are still being produced by a number of manufacturers for sale to the Amish and others who choose to live without electricit, and for remote hunting lodges and vacation cabins located far from power lines. For remote dwellings used only seasonally, propane refrigerators and other propane-powered appliances can be a viable alternative to bringing in electric power.
How They Work
A propane refrigerator uses a sealed piping system containing a mix of ammonia, water and hydrogen. The propane flame heats a boiler filled with an ammonia/water solution. The heated solution bubbles up through a percolator pump, releasing hot ammonia vapor and returning the water to the boiler. The ammonia vapor rises to a condenser where it transfers heat to the room air and turns back into liquid. The ammonia liquid drains down into an evaporator filled with hydrogen gas that reacts with the ammonia to vaporize it again, drawing the necessary heat energy from the interior of the refrigerator. This cools the box and contents. The ammonia-hydrogen mixture drains down to an absorber chamber where the ammonia re-dissolves in water, releasing the hydrogen gas to rise back up into the evaporator. The water-ammonia solution drains down into the boiler to continue the cooling cycle.