BTU (British Thermal Unit) is a measurement unit used to calculate the amount of energy used to raise 1lb of H₂O by 1°F. Thus, the BTU per gallon of propane is the amount of heat a gallon of propane needs to raise the temperature by 1°F. This measurement is essential because propane is primarily used for heating or powering appliances that heat, and BTU will help you understand pricing better.

BTU rating

Basically, every appliance that can be powered by propane is rated by its energy output. This output is usually calculated as BTU.

How much BTU does propane have per gallon?

Per gallon, propane has 91,500 BTUs.  If you want to get a propane tank, you must take the BTU into consideration to know the size you should get. For instance, if you have a grill with a BTU consumption of 60,000, you would see that you don’t necessarily need a huge propane tank. This is because just one gallon of propane at 91,500 BTU will be able to run the grill continuously at maximum capacity for 91,500/60,000 = 1.525 hours.

If you have an HVAC system of 200,000 BTU, you would need about 2.2 gallons of propane to run the system continuously for just one hour.

You should also note that each pound of propane contains approximately 21,548BTUs

Case Study: 20-pound propane tank

How many BTUs are in a 20-pound propane tank?

A 20-pound propane tank holds approximately 4.6 gallons of propane; recall that one gallon of propane contains 91,500BTU. Thus, the amount of propane in a 20-pound tank is 91,500 × 4.6 = 420,900BTUs.

How long will a 20-pound propane tank last for a stove?

We are using a 20-pound propane tank for this because it is one of the most common tanks in use. To calculate how long your heater will last, we have to put two factors into consideration.

●    The burning efficiency of propane

Generally, propane doesn’t burn with 100% efficiency; all things considered, it burns with about 85% efficiency.

●    The BTU capacity of the stove

This factor will affect how much energy demand is placed on the propane tank. For instance, a stove with about 55,000 BTUs will need five times as much energy as one with 11,000BTUs.

Thus, to calculate how long the 20-pound propane tank will last for a stove of 11,000 BTUs, we will first calculate the useful energy. Recall that propane usually burns at 85% efficiency and has approximately 420,900BTUs.

So, useful energy, 420,900BTUs × 85% = 357,765BTU.

Therefore, if the stove burns through 11,000 BTU every hour, a 20-pound propane tank will last for 357,765BTU ÷11,000BTU/hour = 32.5 hours.

Conclusion

You can estimate how long any propane tank you have will last for your heating equipment by utilizing the BTU per gallon of propane and BTU per pound of propane. However, you should note that this is a rough estimate.