How long does a Propane Tank last on a Patio Heater?

How long does a propane tank last on a patio heater? The answer to this question depends on several factors, such as propane tank size, the heating capacity of the patio heater, propane burning efficiency, and the quantity of propane in the tank. 

So, to help you better understand, I will look at all the factors and calculate how long your propane tank would last on your patio heater.

Quick answer: An average patio heater (45,000 BTU/h) lasts 7 hours with a 20lb propane tank, 10 hours with a 30lb propane tank, and 13 hours with a 40lb propane tank. A propane tank’s running duration depends on its size, the heat capacity of the heater, and the burning efficiency of your patio heater. Patio heaters between 10,000 BTU/h and 50,000 BTU/h with a 20lb propane tank would last 30 hours to 6 hours.

Without further ado, I’ll take you to the calculations so that you may be able to understand the concept clearly. 

How long does a propane tank last on a patio heater?

You see, there are different sizes of propane tanks (lb) and patio heaters (BTU/h) available in the market. 

So, we can’t just say how long your propane tank would last on your patio heater without knowing the tank size and your heater’s capacity (in BTU/h). 

Generally, your propane tank would last longer if you use a large propane tank with a small patio heater (less BTU/h). 

So, for your better understanding, I will calculate the time duration for different sizes of propane tanks and patio heaters. 

How long does a 20lb propane tank last on a patio heater?

I’m going to start with a 20lb propane tank as it’s the most commonly used tank size with outdoor patio heaters. 

To calculate how long a propane tank lasts on a patio heater, you can use this formula: 

Propane tank’s effective energy (in BTU) / Patio heater’s capacity (in BTU/h)

So, if we have a propane tank’s effective energy and output heating capacity of a patio heater, we can easily calculate how long a propane tank would last on a patio heater. 

Let me calculate the propane tank’s effective energy for you.  

Effective energy of a 20lb propane tank

One pound of propane contains 21,594 BTU of heat energy (source)

So, a 20lb propane tank contains 431,880 BTU (20lb × 21,592 BTU per lb). 

But, the propane patio heater’s burning efficiency is not 100%. Usually, it’s between 80%-95%. So, here I will assume that the efficiency is 85%. 

Also, propane tanks are often only filled to 80% capacity, allowing the propane to expand safely.

So, considering 85% efficiency and 80% capacity, I’ve calculated the effective energy of a 20lb propane tank: 

431,880 BTU x 0.85 (heating efficiency) x 0.80 (tank fill percentage) = 293,678 BTU

Now we have the effective energy that a 20lb propane tank provides. It’s time to check how long a propane tank lasts on different patio heaters.

How long does a 20lb propane tank last on different patio heaters? 

You can find different-sized patio heaters in the market. The sizes are described by their heating capacity (BTU/h). 

A small patio heater typically consumes 10,000 BTU/h, while a large one produces 50,000 BTU/h per hour. A heater with a high BTU capacity consumes propane faster, so the more BTUs it has, the faster it consumes.

So, I’m going to calculate how long does a 20lb propane tank last on different patio heaters (10,000 BTU/h – 50,000 BTU/h) with this formula:  

Running duration = Propane tank’s effective energy / Patio heater’s capacity (BTU/h)

So, a 20lb propane tank would last 29.36 hours on a 10,000 BTU/h patio heater and 5.87 hours on a 50,000 BTU/h patio heater. 

These hours may vary depending on the usage of propane gas. Your heater may consume more propane than usual if the temperature around it is high or if there are leaks.

How long do different tank sizes last for an average patio heater?

Now, I’m going to calculate how long propane tanks of different sizes would last on a 45,000 BTU/h (average patio heater)

The most commonly used propane tank sizes are 20lb, 30lb, 33 lb, 40lb, 100lb, 420lb, 330lb, 500lb, and 100lb. (source) 

Related: How long does a 100lb propane tank last?

If I have the effective energy of each propane tank, I can easily calculate how long it will last on a 45,000 BTU/h patio heater. 

Now, you can easily choose the propane tank size with your 45,000 BTU/h patio heater according to your requirements. 

Conclusion

A large-sized propane tank usually lasts longer than a small one. But that’s not it. 

To determine how long your propane tank will last on your patio heater, you must know your tank size, output capacity (BTU/h), and the burning efficiency of your patio heater. 

I’ve calculated the time for different propane tanks and patio heaters and created tables for your better understanding. 

I’ve assumed a burning efficiency to be 85% (usually, the burning efficiency of patio heaters is 80%-95%)