View the common conversion factors for energy use in Ireland.
Energy is delivered in many different fuels and sources and can be expressed in terms of volume, mass, energy or emissions. Using the conversion factors below, it is possible to express each fuel or energy source in common units of energy or emissions so that they can be compared and aggregated.
Energy unit types
- Joule (J): Joule is the international unit of energy
- Kilowatt hour (kWh): This is the conventional unit of energy that electricity is measured by and charged for commercially.
- Tonne of oil equivalent (toe): This is a conventional standardised unit of energy (41.868 GJ), and is defined on the basis of a tonne of typical oil having a net calorific value of 41,868 kJ/kg. A related unit is the kilogram of oil equivalent (kgoe), where 1,000 kgoe = 1 toe.
Energy conversion factors
Conversions of fuel quantities -- from physical units to energy units -- require conversion factors expressing the heat obtainable from one fuel unit. Conversion factors are termed the "calorific value" or "heating value" of fuels. Definitions of energy units (toe and J) appear above, while the description of net calorific values (NCV) appears below the table.
|Fuel||Net Calorific Value (toe/t)||Net Calorific Value (MJ/t)|
|Gasoline / Petrol||1.0650||44,589|
|Gasoil / Diesel||1.0344||43,308|
|Residual Fuel Oil / Fuel Oil||0.9849||41,236|
|Fuel||Gross Calorific Value (MJ/m³)||Net Calorific Value (MJ/m³)|
|Natural Gas (2019)||38.6||34.8|
Gross calorific value (GCV) is determined by bringing all the products of combustion back to the original pre-combustion temperature, in particular condensing any water vapour produced. Net calorific value (NCV) is determined by subtracting the heat of vaporisation of the water vapour from the higher heating value. Since the NCV represents the amount of actual usable energy, we adopted NCVs into the methdology for Ireland’s Energy Balance. The differences between net and gross calorific values are typically about 5% to 6% of the gross value for solid and liquid fuels, and about 10% for natural gas.
Source: European Commission (2019) Energy balance guide link.
The table below shows emission factors for CO2 per unit of energy for specific fuels.
|Fuel||tCO₂/TJ (NCV)||g CO₂/kWh (NCV)|
|Gasoline / Petrol||70.0||251.9|
|Gasoil / Diesel||73.3||263.9|
|Residual Oil / Fuel Oil||76.0||273.6|
|Solid Fuels and Derivatives|
Conversion from volume (litres) to mass (tonnes) for liquid fuels requires the densities of the liquids, with the most common fuels shown here.
|Fuel||Density (in litres/tonnes)|
|Diesel / Gasoil||1183|
|Heavy Fuel Oil||1062|
|Pure Plant Oil||1087|
|*Assumes a mixture of 70% propane & 30% butane by mass|
Primary energy conversion factors
Energy consumption can be expressed as total final consumption (TFC) or total primary energy requirement (TPER). TPER accounts for the energy that is consumed and/or lost in transformation, transmission and distribution processes. It is calculated by applying conversion factors, which vary by fuel type, to TFC values. The table below shows the conversion factors for 2019. Historic conversion factors can be downloaded here.
|Fuel||2020 conversion factor|
|Biogas / landfill gas||1.0|
|Light, medium & heavy fuel oils||1.1|
|Marked diesel, road diesel & petrol||1.1|
|Pure biodiesel / bioethanol||1.1|
|Wood briquettes / chips / logs / pellets||1.1|