Originally Posted by Minnesota51
My 18 gal propane tank meter says 1/4 left. My display panel says 1/3.
Full is 14 gals, I believe.
How much do I really have? Can I last a couple of night furnace on for 10 mins about 10 times each night.
They're probably both correct. The gauge on the tank is measuring the absolute level of the propane in the tank. The "gauge" on the panel is reading the amount available compared to the amount the tank holds when "full". Keep in mind "full is only 80% of the absolute capacity.
So the outside gauge is telling you there's 25% of 18 gallons which is 4.5 gallons. The inside gauge is telling you there's 33% of 14.4 gallons which is 4.75 gallons. I doubt either gauge is capable of any closer measurement.