How Long will my Propane Last?

That question can be answered in two different ways.                                                                                        If asking about the lifespan of Propane: 

• Propane does not have a shelf life like gasoline and does not require additives for storage.
• Propane will be of the same quality today as it will be decades from now.
• Because propane is normally stored under natural  Propane pressure, contamination is very unlikely.

If asking about the length of time your fuel supply will last when burning your appliance:                       This is easy to figure out if you know the following:

• The number of pounds of fuel remaining in your propane cylinder.
• That 4.24 lbs of propane equals 1 gallon.
• The BTU/hr demand of your burner or other gas appliance.
• One gallon of propane contains approximately 92,000 BTU's.

The most common tank is a 20 lb cylinder  (sometimes referred to as a 5 gallon cylinder).   These are the same ones commonly used as BBQ tanks.

Here is how the calculations work:    

• First:  Determine your inventory of propane:  Check for the "tare weight" of your tank.  This is the empty weight.  Locate this figure on the embossed data stamped in the steel of your tank.
• Second:  Determine the weight of your propane tank and fuel.  Subtract the tare weight to find out weight of propane.
• Third:  Divide total weight of propane by 4.24 to determine gallons of inventory. 

What do you do with this information?  

A burner or appliance rated at 60,000 BTU/hr (with burner turned on to "High") will burn 60,000 BTU every hour which means consumption of fuel is one gallon of propane every 1.53 hours.  (92,000 BTU/Hr / 60,000 BTU/Hr = 1.53 hours that one gallon would last   Providing the burner remains on "high" you can determine the number of hours your propane supply with last.  To adjust for appliances, like a furnace, that are controlled by a thermostat and only cycle "ON" maybe a few minutes per hour, you would then need to adjust your calculations.  For example if the furnace cycled on for 15 minutes every hour in the winter you would adjust by a factor of 4.  (92,000 BTU/Hr / 60,000 BTU/Hr = 1.53 hours that one gallon would last x 4 = 6.12 hours of furnace usage for each gallon in inventory)

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