Gas

Which gas should I use, propane or butane?

The physical properties of the two gases are similar, and when regulated to the correct pressure, they will perform almost identically. However there are some important differences. Of the two gases, butane has the most advantages.

Litre for litre, it contains around 12% more energy than propane and so you can squeeze more running time into the same sized bottle. (butane is heavier than propane though, so weight for weight it's a pretty close call.)

Butane also burns cleaner than propane and although this isn't normally a serious issue in camping it might be a consideration on the maintenance of gas equipment in the long term.

Finally, while it's not strictly a property of the gas, butane cylinders generally but not always, use clip-on type connections. These are far more convenient than the propane screw type connections, especially if you swap cylinders around regularly.

Conversely, propane has only one advantage over butane - but it's a big one! It is more effective than butane when the temperature is lower so might be better during activities during the colder months.

In order to be usable, the liquid in the bottle must be able to boil into a gas. In the case of butane, this will happen at any temperature above -2 °C, whereas with propane, this figure is much lower, at -42 °C. In the real world, it's not so clear-cut. Whenever some of the liquid boils into gas, the remaining liquid cools. It is therefore possible for the temperature of the liquid to drop to several degrees below ambient. This can easily prevent a butane canister from producing a useful gas supply, even when the outside temperature is several degrees above 0 °C.

So choosing the right gas pretty much boils down to whether you need to use it in freezing (or near freezing) conditions. If this is likely, then propane is a must. If not, then butane has the edge.

Similarities

Both gases burn clearly and have a high calorific value, giving similar flame shapes and heat outputs, and in principle, appliances will burn equally well off either gas.

Differences

However, as gas is drawn off from the cylinder and liquid turns back into gas, the liquid cools down causing the rate of change from liquid to gas to slow down. This effect is particularly marked for butane which will not turn from liquid to a gas below -2 °C, so that on cold days or when the gas is being withdrawn at a high rate, the liquid gets so cold that it delivers very low amounts of gas, or indeed no gas at all.

Thus butane tends to be used for low pressure domestic appliances indoors, or outdoors in the summer only.

Propane continues to turn from liquid to gas at much lower temperatures than butane and thus gives a high pressure of gas on the coldest of days. Although propane cylinders can be used indoors on a temporary basis, they should not be stored indoors because of the higher pressures in them.