Higher Heating Value: what it is and how it is calculated?

When analysing the gas bill, one of the most interesting items is the Higher Heating Value, HHV. This parameter indicates the amount of thermal Energy contained in the gas and directly affects the calculation of the expense. Knowing how it works allows you to read your consumption with greater awareness and better manage your Energy choices.

What is the higher heating value of gas?

The HHV measures the Energy quality of the gas distributed in the local network. It expresses how much thermal Energy is contained in one standard cubic metre of gas, indicated as Smc or SMC, two equivalent graphic forms of the same unit of measurement.

The HHV is measured in kilowatt-hours per standard cubic metre, kWh/Smc, or in megajoules per cubic metre, MJ/m³. In Italy, according to the provisions of ARERA, the Regulatory Authority for Energy, Networks and Environment, the HHV is periodically measured by local distributors and communicated to the Authority, since the heating value of natural gas may vary depending on the composition of the local distribution network.

Higher and lower heating value: what is the difference?

Alongside the higher heating value, there is the lower heating value, LHV, which differs from it in one specific technical aspect: the LHV does not include the heat recoverable from the condensation of the water vapour produced during combustion, which the HHV instead considers.

The HHV is always higher than the LHV: for natural gas, methane, the HHV is conventionally around 10.69 kWh/Smc, while the LHV is typically around 10–13% lower.

This distinction is not only theoretical but has a direct impact on three fundamental aspects of Energy management:

How is the HHV measured and why does it appear on the bill?

The HHV is measured under standard conditions: temperature of 15°C and atmospheric pressure of 1.01325 bar, 1013.25 mbar. These reference conditions, called Standard Measurement Conditions, SMC, make it possible to express gas volumes in a uniform and comparable way, regardless of the environmental conditions at the time of measurement.

The gas meter measures the physical cubic metres consumed. To obtain standard cubic metres, Smc, the distributor applies Coefficient C, a correction factor that takes into account temperature, atmospheric pressure and the altitude of the geographical area, normalizing consumption to national standard conditions.

The HHV comes immediately afterwards: by multiplying the Smc by the local HHV value, the actual Energy expressed in kWh is obtained, which is the true basis for calculating the expense on the bill. The HHV value adopted for the calculation appears on the gas bill as declared and verifiable data.

How does the heating value affect actual consumption?

The HHV is not a fixed value: it can vary from one geographical area to another and, to a lesser extent, during the year, depending on the composition of the gas distributed in the local network. This means that, with the same cubic metres consumed, the cost may differ slightly depending on the HHV applied by the local distributor.

For those considering changing supplier or wanting to better understand how their Energy expense is calculated, it is important to know that the HHV does not depend on the commercial supplier chosen, but on the local gas network distributor.

Monitoring Energy consumption and understanding the parameters that affect the bill is the first step towards managing your expenses with greater awareness, whether you use gas for heating or for the production of domestic hot water.

Frequently asked questions