Which Gas is used in Home Gas Cylinders?
Do home gas cylinders contain LPG, CNG or maybe even Biogas?
There are three major factors that affect the type of gas used in home gas cylinders:
The gas supply situation in your area or country
The economics of the various options
The ambient temperature expected from seasonal weather patterns in your area
Gas Used in Home Gas Cylinders
Home gas cylinders are almost always LPG.
So, you get either propane, butane or a mixture of the two.
Both fall under the broad label of "LPG", as liquefied petroleum gases.
CNG – Compressed Natural Gas – is methane.
CNG supply is also a possibility, but rare for practical and economic reasons.
Biogas, with methane as the primary constituent, has the same limitations.
Major Differences between LPG & CNG
The big difference is in volumetric energy density.
LPG has almost 3x the energy density with 25MJ/L for LPG versus only 9MJ/L for CNG.
In other words, for comparable capacity cylinders, the LPG cylinders will last more than twice as long.
Another major difference is that CNG storage pressures can be more than 10x that of LPG.
For example, LPG pressure is less than 2 MPa whilst CNG is 20 – 25 MPa.
This much higher pressure requires a much heavier and more expensive cylinder or tank.
It also means it is impractical to make them large enough to offset the energy density deficit.
This is due to the size and weight required.
CNG vs LPG for Home Gas Cylinders – Energy Density
Due to the lower energy capacity of a CNG cylinder, they would need replacement more than twice as often.
This means the inconvenience of checking the CNG cylinders and placing orders much more often.
The homeowner would also have to absorb extra freight costs.
This would result from the extra deliveries and added weight.
This is because high pressure CNG cylinders weigh more than twice as much.
For example, an empty 45kg LPG cylinder only weighs approximately 35kg.
An empty CNG cylinder, with comparable volume capacity, is about 108kg.
So, when comparing empty cylinders, a CNG cylinder is 3x the weight.
This also makes it impossible to increase the cylinder size to hold an equal amount of energy.
The cylinder would be too large and too heavy to transport for exchange purposes.
Higher cylinder rental is also likely, as the heavier CNG cylinders cost more.
Finally, the equipment to fill the CNG cylinders is expensive – much more than LPG.
The supplier would need to offset these higher costs in the cost of the gas.
It is the energy density and pressure that affect the comparable convenience and affordability of use.
The Gas Supply in Your Country or Area
Assuming that the gas provided is LPG, it can be propane, butane or a mixture of the two.
For example, the LPG supplied in both the USA and Australia is pure propane.
Some countries, like New Zealand, provide a propane/butane blend.
In certain countries, like England, you can just buy propane or butane.
The relative availability and economics of the different gas types drive the differences.
Weather and Seasonal Effects
Weather, or more specifically temperature, can affect the type of gas used in home gas cylinders.
Propane works better in cold climates.
Propane will continue to vaporise – turn to gas – even in low temperatures.
Propane’s biggest advantage is a lower boiling temperature, at -42°C vs -0.4°C for butane.
Boiling Points for
Propane & Butane
So, propane will continue to vaporise at temperatures well below 0°C.
With butane, when it drops below freezing, you end up with no gas.
Some countries, like Italy, vary the mix by season.
In NZ, they even vary the mix by latitudes, as well as by season.
For example, New Zealand’s North Island and South Islands may receive different mixtures.
The colder regions get a different proportion of propane, vs butane, in winter.
Needless to say, propane is the preferred choice for cold weather climates.
The Name Game
The names for the gases are dependent upon what country you are in.
In Australia, we call it LPG but it is propane.
In New Zealand, LPG is almost always a propane and butane mix.
In the USA, they don’t use the term LPG often. They just call it "Propane".
In some countries, like England, you buy propane or butane by name.
In other countries, they call it "GPL" or "GLP" instead of "LPG".
This is because the acronyms comes from different languages and syntax.
For example, in French it is "gaz de pétrole liquéfié" or in Spanish it is "gas licuado de petróleo".
For many people, the gases supplied in home gas cylinders are indistinguishable and never pose an issue.
However, for others the various gases provide the flexibility for use in diverse conditions.
Either way, LPG is the most common energy product used in home gas cylinders.
Comments, questions or feedback?
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.