How Long Does a 9kg Gas Bottle Last – How Many MJ in a 9kg Gas Bottle

How Long Does a 9kg Gas Bottle Last – How Many MJ in a 9kg Gas Bottle

How long a 9kg gas bottle lasts is determined by the gas consumption of the appliances attached. You also need to know how many MJ in a 9kg gas bottle.

The MJ/hour rating of the appliance is the hourly gas consumption.

Divide the MJ content of the gas bottle by this MJ/hour number and you get how long it will last. 

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?

Here are some typical examples:

♦ A 9kg gas bottle lasts ≈ 26 – 29 hours with 1 Burner on a Full Sized BBQ

♦ A 9kg gas bottle lasts ≈ 6 – 7 hours with 4 Burners on a Full Sized BBQ

♦ A 9kg gas bottle lasts ≈ 44 – 69 hours with 1 Burner on a Compact BBQ

♦ A 9kg gas bottle lasts ≈ 22 – 29 hours with 2 Burners on a Compact BBQ

♦ A 9kg gas bottle lasts ≈ 22 – 29 hours with a 35 MJ Patio Heater ≈ 12 hours

♦ A 9kg gas bottle lasts ≈ 36 hours with a 12 MJ Table Top Heater

These estimates are based on running at maximum setting/rate.

Duration would be longer on lower settings.

How Long Does LPG Last

How long does LPG last… indefinitely.

LPG shelf life is unlimited.

The only limiting factor is the gas bottle itself.

Assuming it is taken care of and not allowed to rust, it could last 20 years or more.

Gas bottles typically need re-inspection every 10 years to refill the gas bottle but you can use it beyond 10 years, if safe to do so.

Calculations Based on MJ/hr or BTU/hr

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

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.

Here are some estimates based on 441 MJ in a full 9kg BBQ gas bottle:

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:

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.

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%.

How Long Does Patio Gas Last

Patio gas will last 12 hours with a 35 MJ patio gas heater, based on a 9kg (20 lb) patio gas bottle. This is assumes using the HIGH setting and will last longer if turned down.

♦ Patio gas will last ≈ 26 – 29 hours with 1 Burner on a Full Sized BBQ

♦ Patio gas will last ≈ 6 – 7 hours with 4 Burners on a Full Sized BBQ

♦ Patio gas will last ≈ 44 – 59 hours with 1 Burner on a Compact BBQ

♦ Patio gas will last ≈ 22 – 29 hours with 2 Burners on a Compact BBQ

♦ Patio gas will last ≈ 12 hours with 35 MJ Patio Heater

♦ Patio gas will last ≈ 36 hours with 12 MJ Table Top Heater

Here are some estimates on how long patio gas will last:

How Long Does a 4kg Gas Bottle Last

A 4kg gas bottle does last about 3 to 4 days cooking a meal a day on a 4 burner BBQ grill, assuming a one hour cook time per meal.

A 9kg gas bottle (patio gas) will last about 15 hours, when cooking with a small 2 burner compact BBQ used on high.

It will last even longer on lower settings or if only one burner is turned on.

Patio gas (4kg) will last 6 hours with a 35 MJ patio gas heater. This is based on using the HIGH setting and will last longer if turned down.

A small table top heater will last about 18 hours on a 4kg gas bottle.

A 4kg BBQ gas bottle will last a little over 3 hours with a large 4 burner BBQ.

A 1-burner compact BBQ will last 22 hours on a 4kg gas bottle. These durations all assume the burners are set on maximum.

How Long Does a 13kg Gas Bottle Last on a BBQ

How long does a 13kg gas bottle last on a BBQ would be anywhere from about 9.4 hours for a large 4-burner BBQ to 84.7 hours for a compact 1-burner BBQ.

A 13kg is 44% larger than a 9kg so if you multiply the 9kg figures above times 1.44, you will get how long a 13kg gas bottle lasts.

For example, a traditional BBQ with 4 x 15MJ burners will last 10.5 hours (7.3 x 1.44 = 10.5 hours).

Or, even easier, just use the 13kg chart below:

How Long Will a 20 Pound Propane Tank Last

How long will a 20 pound propane tank last (how long does BBQ gas last) is determined by dividing the hourly consumption of your gas appliance into the available energy content of the propane BBQ gas tank.

You get the number of hours the gas bottle will last.

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

Here are some estimates for how long does a gas bottle last:

Read more to learn exactly how to calculate how long does a gas bottle last 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 How Long Does a Gas Bottle Last

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 15×2=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 how long does a gas bottle last.

BBQ Example 2:

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

So 417÷10=41.7 hours of running time how long does a gas bottle last.

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% for how long does a gas bottle last.

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

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

MJ – Megajoule

Megajoules 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.