BBQ Gas users, please see How Long Will a 9kg BBQ Gas Bottle Last
How Long Does a Gas Bottle Last  How Long Does a 45kg Gas Bottle Last
A 45kg gas bottle could last less than 22 days or up to 489 days or more. A 45kg gas bottle (45 kg gas cylinder) will last around 67 weeks with a 4 person household using gas for cooking and hot water. This is based on water saving shower heads and 810 minute showers. This may drop a bit in winter, as the incoming water is colder.
A family of 4 with a 3 bedroom house using a 25MJ portable heater, like a Rinnai Avenger 25, will have a 45kg gas bottle last about 2 weeks in really cold weather, including cooking and hot water.
My wife and I live in the cold Blue Mountains and we get about 16 weeks from a 45kg gas bottle for just cooking and hot water. That drops to 23 weeks when we add the use our Rinnai Avenger to heat the entire 3bedroom house in cold weather, as heating is not dependent upon the number of people.
Of course, if you have teenagers taking hour long showers or you are using old full flow shower heads, your consumption will be more. Other variables like climate, insulation, outdoor temperature, indoor set temperature, size of windows, weather stripping, window coverings, floor covering, ceiling height and subfloor style can also affect your usage.
How Long Does a 45kg Gas Bottle Last  Examples:
A 45kg gas bottle will last 244 days based on a 9 MJ cooktop burner used for 60 minutes per day. A 45kg gas bottle (45 kg LPG cylinder) lasts 44 days fueling a 25 MJ Gas Fireplace used for 2 hours per day.
Here are some typical examples of how long a 45kg gas bottle lasts (numbers are rounded):
♦ 16 L/min Hot Water used for 20 minutes per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 52 days
♦ 16 L/min Hot Water used for 30 minutes per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 35 days
♦ 9 MJ Cooktop Burner used for 60 minutes per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 244 days
♦ 9 MJ Cooktop Burner used for 90 minutes per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 163 days
♦ 15 MJ Gas Heater used for 3 hours per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 49 days
♦ 15 MJ Gas Heater used for 4 hours per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 37 days
♦ 25 MJ Gas Fireplace used for 2 hours per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 44 days
♦ 25 MJ Gas Fireplace used for 3 hours per day = a 45kg gas bottle (45 kg LPG cylinder) lasts 29 days
How long does a LPG cylinder lasts depends on the cylinder size and the gas load upon it.
These estimates for how long does a gas bottle last are based on running at maximum setting/rate.
A gas bottle does last longer on lower settings.
How Long Does a 45kg Gas Bottle Last  Chart:
Here are some estimates on how long a 45kg gas bottle (45 kg LPG cylinder) will last:
How Long Does a 45kg Gas Bottle Last?  
Gas Heater  2 hrs/day  3 hrs/day  4 hrs/day 
• 15 MJ Heater  73 days  49 days  37 days 
• 25 MJ Heater  44 days  29 days  22 days 
Gas Hot Water  10 min/day  20 min/day  30 min/day 
• 16L/Min 124 MJ  105 days  52 days  35 days 
• 26L/Min 199 MJ  66 days  33 days  22 days 
Gas Cooktop  30 min/day  60 min/day  90 min/day 
• 9 MJ Burner  489 days  244 days  163 days 
• Durations shown assumes that you use the appliance on the maximum setting.
• Gas consumption would be less, and the duration longer, on lower settings.
• Numbers have been rounded and are only estimates.

Read more to learn exactly how to calculate for your home…
47kg Propane Gas How Long Does It Last  How Long Does 47kg Propane Gas Last
A 47kg propane gas could last less than 23 days or up to 511 days or more. A 47kg propane gas will last around 67 weeks with a 4 person household using gas for cooking and hot water, This is based on water saving shower heads and 810 minute showers. This may drop a bit in winter, as the incoming water is colder.
A family of 4 with a 3 bedroom house using a 25MJ gas heater will have a 47kg propane gas last about two weeks in really cold weather, including cooking and hot water.
My wife and I live in the cold Sydney Blue Mountains and we get about 16 weeks from a 45kg gas bottle for just cooking and hot water. That drops to 23 weeks when we use our 25MJ gas heater to heat the entire 3bedroom house in cold weather, as heating is not dependent upon the number of people. A 47kg propane gas would last about 4% longer.
Of course, if you have teenagers taking hour long showers or you are using old full flow shower heads, your consumption will be more. Other variables like climate, insulation, outdoor temperature, indoor set temperature, size of windows, weather stripping, window coverings, floor covering, ceiling height and subfloor style can also affect your usage.
A 47kg propane gas will last 254 days when used just for cooking, based on a 9MJ cooking burner used for 60 minutes per day. A 47kg propane gas does last 46 days fueling a 25 MJ Gas Fireplace used for 2 hours per day.
Here are some more typical examples of how long a 47kg propane gas does last (numbers are rounded):
♦ 16 L/min Hot Water used for 20 minutes per day = a 47kg propane gas bottle lasts 54.3 days
♦ 9 MJ Cooktop Burner used for 60 minutes per day = a 47kg gas bottle lasts 254 days
♦ 15 MJ Gas Heater used for 3 hours per day = a 47kg gas bottle lasts 51 days
♦ 25 MJ Gas Fireplace used for 2 hours per day = a 47kg gas bottle lasts 46 days
These estimates are based on running at maximum setting/rate.
A gas bottle lasts longer on lower settings.
The big range is because of the variability of the gas load upon it, from a very large burner to a very small burner.
“How long does a gas bottle last?” To answer it correctly you need to know the size of the gas bottle and the gas consumption of the gas appliances.
Whether it's how long does a 45kg gas bottle (45 kg LPG cylinder) last in Australia or a 47kg propane gas in the UK, the question remains the same.
There is no single answer to how long does a gas bottle last and a bit of explanation is required to get to the answer for your specific situation. Figuring out how long does a gas bottle last is actually easy…
How Long Does a 14.2kg Gas Bottle Last
A 14.2kg cooking gas bottle will last from about 9 days to 81 days, depending upon burner size and amount of use. If you use a small 5MJ burner for 30 minutes per day, the gas bottle will last 81 days. If you use a large 15MJ wok style burner for 90 minutes per day, the gas bottle lasts 9 days.
Measured in hours, a 14.2kg cooking gas bottle would last from about 40.4 hours to 13.5 hours, depending upon burner size and amount of use. This gas bottle estimate assumes having the burner on the maximum setting. The gas bottle will last longer on lower settings.
A 14.2kg cooking gas bottle contains about 202MJ of energy. To calculate how long your cooking gas bottle will last, just divide the 202MJ by the burner size. If you use more than one burner, you need to add their MJ ratings together before you divide.
How Long Will a 14.2kg Gas Bottle Last?  
Gas Cooktop  Total Hours  30 min/day  60 min/day  90 min/day 
• 5 MJ Burner  40.4 hours  81 days  40 days  27 days 
• 9 MJ Burner  22.4 hours  45 days  22 days  15 days 
• 15 MJ Burner  13.5 hours  27 days  13 days  9 days 
• Durations shown assumes that you use the appliance on the maximum setting.
• Gas consumption would be less, and the duration longer, on lower settings.
• Numbers have been rounded and are only estimates.

How Long Does a 13kg Gas Bottle Last BBQ
A 13kg cooking gas bottle will last from about 8 days to 74 days, depending upon burner size and amount of use. If you use a small 5MJ burner for 30 minutes per day, the gas bottle will last 74 days. If you use a large 15MJ wok style burner for 90 minutes per day, the gas bottle lasts 8 days.
Measured in hours, a 13kg cooking gas bottle would last from about 37 hours to 12.4 hours, depending upon burner size and amount of use. This gas bottle estimate assumes having the burner on the maximum setting. The gas bottle will last longer on lower settings.
A 13kg cooking gas bottle contains about 185MJ of energy. To calculate how long your cooking gas bottle will last, just divide the 185MJ by the burner size. If you use more than one burner, you need to add their MJ ratings together before you divide.
How Long Does a 13kg Gas Bottle Last BBQ  
Gas Cooktop  Total Hours  30 min/day  60 min/day  90 min/day 
• 5 MJ Burner  37 hours  74 days  37 days  25 days 
• 9 MJ Burner  20.5 hours  41 days  20 days  14 days 
• 15 MJ Burner  12.4 hours  25 days  12 days  8 days 
• Durations shown assumes that you use the appliance on the maximum setting.
• Gas consumption would be less, and the duration longer, on lower settings.
• Numbers have been rounded and are only estimates.

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 reispection every 10 years to refill the gas bottle but you can use it beyond 10 years, if safe to do so.
How Long Does a Gas Bottle Last for Hot Water
How long a gas bottle lasts for hot water could be anywhere from 22 days to 105 days or longer for a 45kg gas bottle, depending on how much hot water you use. My wife and I have 45kg gas bottles last for more than four months using it for hot water and cooking.
If you use your gas for cooking only, you would expect the 45kg gas bottle to last anywhere from 12 months to 18 months, as cooking uses much less gas and the gas bottle will last longer than with hot water.
We are on rain water so we take quick showers but they are still about the average of 8 minutes long, we have a 26L/min hot water unit and we have water saving shower heads. We use cold water for laundry and the dishwasher, so aside from washing hands, showers are the main hot water consumption.
On the other hand, a large family with teenagers who take long showers will use gas much quicker. Here is a table showing the number of days a 45kg gas bottle will last for hot water.
How Long Does a Gas Bottle Last for Hot Water  
Gas Hot Water  10 min/day  20 min/day  30 min/day 
• 16L/Min 124 MJ  105 days  52 days  35 days 
• 26L/Min 199 MJ  66 days  33 days  22 days 
• Durations shown assumes that you use the hot water on the maximum flow rate
• Gas consumption would be less, and the duration longer, on lower settings.
• Numbers have been rounded and are only estimates.

Calculations Based on MJ/hr or BTU/hr
How long does a gas bottle last depends on the appliances used.
Gas appliances energy consumption is rated in MJ/hr or BTU/hr.
Gas bottle energy content is expressed in MJ or BTU.
By dividing the MJ consumption into the gas bottle MJ content, you get the number of hours that the gas bottle will last.
The same is true for BTUs.
Multiply the results by 1.044 (4.4% more) for a 47kg propane gas bottle.
Important Reference Information
To get started, here are some numbers you will need to know for your reference:
Energy equivalent conversion:
1kW/hour = 3.6MJ
1kg of LPG = 1.96 litres of LPG (propane)
LPG  propane  contains approximately 25MJ per litre
A 45kg gas bottle (45 kg LPG cylinder) contains about 88 litres of LPG or 2200MJ of energy
Multiply the results by 1.044 (4.4%) for a 47kg propane gas bottle.
How to Use Less Gas at Home  Efficiency Matters
How to use less gas at home is all about the appliance efficiency ratings.
MJ inputs and kW outputs are directly related but are affected by the efficiency of the appliance.
For example, a 25MJ heater with a 5.8 Star energy rating has an output of 6.2kW.
Now, if you do the maths, dividing 25MJ ÷ 3.6MJ, you would expect that the output to be 6.94kW, not 6.2kW.
The difference is that, at 5.8 Stars, the heater is 89.3% efficient.
No gas appliance is 100% efficient, which is why we have the Star rating system to judge the relative performance of different models.
Heater LPG Gas Consumption Calculation:
A 15MJ 5.8 Star gas heater running at its maximum setting will last approximately 147 hours on a 45kg gas bottle (45 kg LPG cylinder), based on the LPG gas consumption calculation.
We know this because the 45kg gas bottle (45 kg LPG cylinder) contains 2200MJ.
The math is as follows: 2200MJ ÷ 15MJ = 147 hours.
However, this same heater, when set on low, consumes 6.0MJ.
So, if you operate it on low only, it will last 367 hours (2200MJ ÷ 6MJ = 367 hours).
As most people would vary the settings, depending on the temperature, the gas bottle will last some duration between 147 and 367 hours.
So, if you use your heater for four hours every evening, you would expect your gas bottle to last anywhere from 37 to 92 days.
Remember to multiply the results by 1.044 (4.4%) for a 47kg propane gas bottle.
Hot Water LPG Gas Consumption Calculation:
A 16L/min 130MJ 5.0 Star continuous flow hot water heater running at full capacity will last for 16.9 hours of actual run time on a 45kg gas bottle (45 kg LPG cylinder), based on the LPG gas consumption calculation.
This equates to about 204 five minute showers.
However, the water heater can run at a flow rate of as little as 3.5L/min.
When running slower, the unit will selfmodulate and consume less gas.
This would increase the run time by roughly 4X or to about 68 hours.
This equates to around 816 five minute showers.
Assuming you use hot water for other things, as well, totalling 20 minutes per day at maximum, your gas bottle would last about 50 days.
Cooktop LPG Gas Consumption Calculation:
Cooktop burners are an even greater challenge to calculate.
The burners on a particular cooktop could vary from 5MJ for the smallest burner to 9MJ for a medium burner, 12MJ for a large burner and 15MJ for a wok burner.
Add to this the fact that each can be run at less than maximum and you can see the maths challenge.
If you use the medium 9MJ burner as the average, you get 244 hours of cook time on a 45kg gas bottle (45 kg LPG cylinder), based on the LPG gas consumption calculation.
Not surprisingly, many cooking customers report that a single bottle can last more than a year.
LPG Gas Consumption Calculation if You have Multiple Appliances
Now the math gets really challenging!
You really can’t add the MJ ratings of all of the appliances together, as they would rarely be used all at the same time and for the same duration.
The easiest method of calculating would be to estimate how long you would use each appliance per day and total their daily consumption.
Using the previous appliance examples:

You use your hot water for 20 minutes per day on maximum. This equals 43MJ of consumption.

You use your heater, on maximum, for 4 hours every evening. This equals 60MJ of consumption.

You cook, using one medium 9MJ burner, on maximum, for 45 minutes per day. This equals 7MJ of consumption.

Adding these all together, you are using 110MJ per day. Based on this, you would expect a 45kg gas bottle (45 kg LPG cylinder) to last for approximately 20 days. (2200MJ ÷ 110MJ = 20), based on the LPG gas consumption calculation.
Remember to multiply the results by 1.044 (4.4%) for a 47kg propane gas bottle.
You may also wish to see:
How Much Gas is Left in the Gas Bottle
Tips for Not Running Out of Gas
Ordering LPG: 3 Common Mistakes To Avoid
12 Handy “How To” Guides for LPG & Gas Appliances
How Long Does a Gas Bottle Last in a Heater  A 9kg Example
A typical patio heater would be about 35MJ (33,173 BTU). Since a 9kg gas bottle has 441MJ (417,987 BTU) of energy content, a gas bottle will last 12 hours in a heater rated at 35MJ. How long a gas bottle lasts in a heater depends on the burner size.
45kg gas bottle (45 kg LPG cylinder) LPG Gas Consumption Calculation Chart
For those who can't be bothered with the maths, here is a quick LPG gas consumption calculation chart
Remember to multiply the LPG Gas Consumption Calculation Chart by 1.044 (4.4%) for a 47kg propane gas bottle.
A Megajoule or MJ Probably Isn't What You Think
What is a megajoule and why does it matter when I buy a gas heater or hot water heater or other gas appliance?
What size gas heater or hot water system should I buy?
How do I compare gas appliance prices?
Many people think they know but you might be surprised by the real answer.
A MJ is NOT This...
I recently watched a product video produced by a major Australian retailer.
In it, a “Product Expert” reviews a Rinnai gas heater.
He did a fair job of explaining the features, even if you could get the same information from the Rinnai web site or product brochure.
The problem was that the presenter lost me in the second sentence when he said: “That’s 13MJ of heat.”
He also makes a similar statement in at least one other video.
To quote the popular Gen Y meme… EPIC FAIL!
Sorry, but there is nothing worse than an “expert” giving out bad advice.
Please let me explain…
Gas Consumption = MJ
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.
Appliance output is often expressed as just kW.
Energy Efficiency  Star Ratings
Star ratings were developed to provide consumers with an easy way of comparing the energy efficiency of different models of gas heaters and hot water systems.
All States now require both LPG and Natural Gas heaters to be tested and certified, under AS4553, by independent testing organisations, such as the AGA and SAI Global.
The Star Rating is based on net heater efficiency.
Net heater efficiency is calculated on the basis of a combination of efficiency measures and takes into account all gas and electrical inputs.
It basically compares the amount of raw energy input consumed by the heater in comparison to the heat energy output provided.
This is calculated as a percentage and then translated into the corresponding Star Rating.
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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.