Propane – Refill or Exchange – Which Is Cheaper?

Propane Tanks Since propane volume changes with pressure and temperature, propane tanks are designed to take about 20% more volume than the nominal or stated size to allow for expansion. All propane tanks are stamped with a “tare weight” or “T.W.” on the collar of the tank. Sometimes called the “unladen weight” the tare weight is the weight of an empty container. A full tank will weigh an amount equal to the tare weight and the tank capacity. In other words if the tare weight of a 20 pound tank is 17 pounds, it should weigh 37 pounds when full. There is also a date on the collar of the tank. The tank may be used for 12 years from the stamped date after which time it must be recertified for an additional five years. However, the cost and inconvenience of re-certifying almost always outweighs the price of a new tank. Cylinder Exchange Read the signs carefully and you will see a reference to something like “Net Weight 15 Lbs (68KG)”.  Your 20 pound tank only has 15 pounds of propane – not the 20 pounds you thought you were buying! It is interesting that this little fact is printed in the un-bolded print. Cylinder exchange provides you with only 75% of the gas you get when refilling a cylinder tank. One gallon of propane weights about 4.25 pounds at sea level. A 20 pound cylinder therefore should contain about 4.7 gallon when full (20/4.25 – 4.71). However with this cylinder exchange the consumer is only getting 15 pounds or 3.53 gallons (15lbs /4.25 pounds per gallon). The price...