What is the difference between rich and lean gas? Does this have an impact on my bill?

Rich gas and lean gas are the two types of natural gas that are distributed via different networks. The difference between them is their calorific value, i.e. a different quantity of energy.

In other words, 1 m³ of lean gas provides less energy than 1 m³ of rich gas. To take a concrete example, to heat the same volume of water for a bath, you will need more lean gas than rich gas.

However, this difference does not have any impact on your bill, as your supplier bases this on the quantity of energy that you have actually used and not on the quantity of gas supplied to you. After all, your bill is calculated on the basis of the amount of energy (number of kWh), and not on the amount of gas you have consumed (number of m³).

Different gases, but a fair rate for everyone

When using a wood-burning stove, no-one would want to pay the same price for a cubic metre of pinewood as for a cubic metre of oak. The volume may be the same, but pine wood contains far less bulk (and hence less energy) than oak.

The same is true of gas. The two sorts of gas have a different calorific value, i.e. a different quantity of energy.

Rich gas

comes mainly from Norway, the United Kingdom, Germany or Qatar
contains an average of 11.4 kWh per m³

Lean gas

came from The Netherlands (Slochteren): this gas supply was discontinued in 2023
contains an average of 10.3 kWh per m³ (type of gas that is found in Brussels)

The combustion of 1m³ of lean gas releases less energy than the combustion of 1m³ of rich gas.

Why are there different types of natural gas?

As its name indicates, natural gas is not an industrial product but a natural one. Its composition varies over time and depends on the geological layers in the subsoil of the place of origin. This is why the gas network operators recalculate the calorific value every month.

No more lean gas in Belgium

The Netherlands have stopped gas production in Slochteren.

Gas reserves are indeed running out and so the Dutch government has decided no longer to supply to Germany, northern France and a third of Belgium. The shutdown took effect in october 2023.

In Brussels, the entire network has been switched over to rich gas since the end of 2022.