This is probably old hat to many, but first time I realized how "one" could estimate how long your propane could / should last.
Did you know that a gallon of propane (Liquid Propane, if you prefer) has about 91,500 BTU (British Termal Unit) of energy per gallon?
A full (80%) 20 # cylinder holds 4.7 gallons of propane; a full 30 # cylinder holds 7.1 gallon or propane, again with a good fill.
So about the calculations.
So, with 4.7 gallons in a 20# cylinder contains 430,050 BTU of energy... a 30# 649,650 BTUs.
All appliances should show their BTUs (per hour).
My furnace 19,000 BTU/hr... water heater 12,000... etc.
Dividing the BTU / hour of the appliance tell you how long this appliance could run continuously on the tank. The trick is estimating how long they run per hour. You know how long a furnace might run or how long you used the stove, but a water heater would be harder to tell.
So, if you divide 430,500 by 19,000 (some know where this example comes from
) it tells us we should get a little over 22 hours out of that 20# tank of continuous use. If it ran 30 minutes per hour, we could get 44 hours of heat from one tank, in theory.
A 45,000 furnace would run a little over 2 (TWO) hours from a tank. It is obvious and eveyone knows a 20# cylinder has no place in big RV. But, seeing the number is interesting.
This water heater alone (12,000 for the Dometic 6 gallon) could run 35.8 hours continously.
My little 6,000 catalytic could run over 71 hours.
Propane weighs 4.2# per gallon, by the way, so 4.7 gallons weighs about 19.7#. The empty tank weight is about 17#, which is also called tare weight. Add together, a full tank should weigh around 37# or slightly over. The 30# weighs about 55# total.
Did you know that companies that exchange cylinders (20#ers) underfill them, "full" might only be 3.5 gallons? If the price is low enough it still could be less exensive than having a gas company fill yours. Personally, I would rather keep my tanks and only exchange if is an emergency.
I need bigger tanks! I need a raise.
Sorry.... my OCD (CDO) is glaring, huh?