What size LP Storage Tank Do I Need?

Good question? And, Orion Propane Services can quickly and easily provide that answer for you. Here is some information that may help show the path this decision will take. Let’s get the “science” jargon about propane out of the way first. A single gallon of liquid propane produces approximately 91K BTU’s of energy per hour. A single 120 gallon LP tank will produce approximately 150-200K BTU's of propane vapor per hour at an outdoor temperature of 60℉ with the LP tank at 60% full. However, the vapor production of the liquid propane in the tank(s) is dramatically reduced as the outside temperature drops and the LP tank(s) becomes further depleted of propane. There are many variables in determining exactly how much LP vapor is produce at any given time. But, as a rule of thumb, under sizing an LP tank can result in failure of the LPG system to properly run the aggregate BTU demand required.

The aforementioned information is based on the physical properties of propane. What is most important to remember is that the propane capacity of an LP storage tank used to supply a LPG system is not enforceable by the state, or local codes. Any number of LP tanks, or size LP tank can be used for any LPG system. The only issue that is enforceable, and must be followed by licensed LPG technicians, is that properly sized LPG piping and components are used from the propane supply (LP storage tank) to the combined BTU demand of the LPG appliances connected to it. 

Adding a very high BTU demand on your LPG system that also runs the LPG appliances in your home, such as an LPG emergency stand-by generator can change the game dramatically. Many seperate the LPG system that services their homes, or businesses from the LPG generator by providing the generator with its own LP storage tank(s). The biggest reason for this decision is that the unpredictable nature of the LPG generator regarding how often it will run creates problems for the propane provider. It makes it impossible to even roughly predict when they should deliver propane automatically. The concern of inadvertently running the customer dry and freezing up their homes becomes very real. So, most propane providers require home and business owners with LPG generators connected to a central heating system to be on Will Call delivery status.

Regarding LPG emergency generator BTU demands, below are the approximate LPG BTU usage rates for Generac/Honeywell LPG generators. These numbers represent the propane vapor burned per hour at Full throttle. Orion Propane Services offers the corresponding recommended number of tanks and sizing.


9Kw = 137,000 BTUs per Hr. = (1) 120 gal LP Tank

11Kw = 182,500 BTUs per Hr. = (2) 120 gal LP Tanks (or Lg. Single Tank Equivalent Capacity or More)

16Kw = 292,320 BTUs per Hr. = (3) 120 gal LP Tanks
 (or Lg. Single Tank Equivalent Capacity or More)

22Kw = 335,000 BTUs per Hr. = (4) 120 gal LP Tanks (or Lg. Single Tank Equivalent Capacity or More)