LPG Gas Blog
Home LPG users, please see How Long Do 45kg Gas Bottles Last

How Long Does a BBQ Gas Bottle Last?

This is one of the most frequently asked questions. 

 

The answer depends on the gas consumption rating of the BBQ or patio heater being used.

 

Quick BBQ Gas Bottle Capacity Facts:

 

9kg in pounds = 19.8416 lbs

 

8.5kg in pounds = 18.7393 lbs

How Long Do 9kg Gas Bottles Last? The Short Answer

How long do 9kg or 20lb gas bottles last?All outdoor gas appliances — like BBQs and patio heaters — are rated by energy consumption, in either megajoules (MJ) or BTUs per hour.

9kg or other sizes of BBQ gas bottles-cylinders, have a known energy content based on their capacity and the energy content per unit of the LPG (propane).

By dividing the hourly consumption of your gas appliance into the available energy content of the LPG gas bottle, you get the number of hours that the gas bottle-cylinder will last.

There are 441 MJ in a full 9kg BBQ gas bottle.

Here are some estimates:

How Long a 9kg BBQ Bottle Lasts
How Long Will a 9kg
BBQ Gas Bottle Last?
Traditional BBQ 1 Burner 4 Burners
  • 15MJ Burners 29.4 hours 7.3 hours
  • 17MJ Burners
25.9 hours
6.5 hours
     
Compact BBQ 1 Burner 2 Burners
  • 7.5 MJ Burners 58.8 hours 29.4 hours
  • 10MJ Burners 44.1 hours 22 hours
     
Gas Patio Heaters 1 Burner -
  • 35MJ Burner 12.6 hours -
     
Table Top Heater 1 Burner -
  • 12MJ Burner 36.7 hours -
 • Duration Shown assumes that you use the burners on the maximum setting.
 • Gas consumption would be less, and the duration longer, on lower settings.
 • Result numbers have been rounded.

How Long Will a 20 Pound Propane Tank Last?

By dividing the hourly consumption of your gas appliance into the available energy content of the propane tank, you get the number of hours that the propane tank will last.

There are 420,909 BTU in a full 20 pound propane tank.

Here are some estimates:

How Long a 20lb Propane Tank Lasts
How Long Will a 20lb
Propane Tank Last?
Traditional BBQ 1 Burner 4 Burners
  • 14,220 BTU Burner 29.6 hours 7.4 hours
  • 16,100 BTU Burner
26.1 hours
6.5 hours
     
Compact BBQ 1 Burner 2 Burners
  • 7,110 BTU Burner 59.2 hours 29.6 hours
  • 9,480 BTU Burner 44.4 hours 22.2 hours
     
Gas Patio Heaters 1 Burner -
  • 33,180 BTU Burner 12.7 hours -
     
Table Top Heater 1 Burner -
  • 11,380 BTU Burner 37.0 hours -
 • Duration Shown assumes that you use the burners on the maximum setting.
 • Gas consumption would be less, and the duration longer, on lower settings.
 • Result numbers have been rounded.

Read more to learn exactly how to calculate for your home…

Basic Background Information

Appliance gas consumption is expressed in Megajoules or MJ of energy.  

 

The total MJ consumption is a function of the burner size and the number of burners. 

 

For example, a traditional sized gas BBQ would have 4 or 6 burners and these usually range from 12MJ to 19MJ each. 

 

15MJ to 17MJ burners are the most typical.

 

Some of the new compact portable BBQs would have only one of two burners and the burners would range from around 7.5MJ to 11MJ. 

 

10MJ would be typical.

 

Just to make it a bit more challenging, some BBQ manufacturers, like Weber, rate their burners in BTU

 

1MJ equals 948BTU, so to get an equivalent number of Megajoules, just divide the BTU burner rating by 948.

 

One litre of LPG has approximately 25MJ of energy content.  

 

An 8.5kg gas bottle contains just a bit less than 17 litres or approximately 417MJ of energy.

How To Calculate  

So, to determine how long the 8.5kg gas bottle will last, you just divide 417 by the MJ rating of the BBQ or patio heater. 

 

You should be able to find the MJ rating of the burners in your Owner's Manual or on the manufacturer's web site. 

 

BBQ Example 1: 

 

You turn on 2 burners set to high. 

 

Each burner is rated at 15MJ so that's 15x2=30MJ/hour of gas consumption. 

 

Then divide that into 417 (the number of MJ in the 8.5kg bottle) to get the running time: 417÷30=13.9 hours.

 

BBQ Example 2: 

 

You have a single burner compact BBQ with a 10MJ rated burner. 

 

So 417÷10=41.7 hours of running time.

 

To make it even easier, you can use the table below.

 

In the USA?

 

If you are in the USA, a typical 20 pound propane tank is filled with 17 pounds of propane (LPG). 

 

This converts to approximately 7.7kg, 15.1L or 377MJ (357,000BTU). 

 

So, you would need to reduce the times, in the table below, by about 9%.

 Answers shown are just examples, as MJ ratings will vary by manufacturer and model:

 

How Many Hours Will a BBQ Gas Bottle Last?

A Megajoule or MJ Probably Isn't What You Think

What is a megajoule and why does it matter when I buy a gas BBQ or heater?

Many people think they know but you might be surprised by the real answer.

Gas Consumption = MJ

MJMegajoules per Hour (MJ/hr) ratings on appliances actually indicate the gas consumption of the appliance, not the heat output. 

It is often expressed as just MJ. 

On the other hand, heat output must also take into account the relative energy efficiency ratings of the models being compared.

How is it pronounced?  Say it as if it were spelled "mega jewel" or "mega jewels", not "mega jowl".

Heat Output = kWh

Kilowatt Hour (kWh) is how gas heater output is measured.  3.6 MJ of input equals 1kWh of output at 100% efficiency. 

However, no gas appliance is 100% efficient. 

That is why we have Star Ratings, so we can compare relative efficiency between models on some types of appliances. 

Appliance output is often expressed as just kW.

 

View More LPG Gas Blogs

Comments, questions or feedback?

Please Email us at: This email address is being protected from spambots. You need JavaScript enabled to view it.

The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.

 

Open new LPG account