View the common conversion factors for energy use in Ireland.

Energy units

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

From Multiply by    
toe 1 11.63 41.868
MWh 0.086 1 3.6
GJ 0.02388 0.2778 1

Calorific values

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.

FuelNet Calorific Value (toe/t)Net Calorific Value (MJ/t)
Crude Oil 1.0226 42,814
Gasoline / Petrol 1.0650 44,589
Kerosene 1.0556 44,196
Jet Kerosene 1.0533 44,100
Gasoil / Diesel 1.0344 43,308
Residual Fuel Oil / Fuel Oil 0.9849 41,236
LPG 1.1263 47,156
Petroleum Coke 0.7663 32,084
Coal 0.6650 27842
Milled Peat 0.1860 7,787
Sod Peat 0.3130 13,105
Peat Briquettes 0.4430 18,548
Fuel Gross Calorific Value (MJ/m³) Net Calorific Value (MJ/m³)
Natural Gas (2021) 39.0 35.2

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 methodology 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.

Emission factors

The table below shows emission factors for CO2 per unit of energy for particular fuels. Definitions of energy units (toe and J) and net calorific values (NCV) appear above. TJ stands for terajoule or 1012 joules. Values for Petroleum Coke, Milled Peat, Natural Gas and Electricity change annually.

Fuel tCO₂/TJ (NCV) gCO₂/kWh (NCV)
Liquid Fuels    
Gasoline / Petrol 70.0 251.9
Kerosene 71.4 257.0
Jet Kerosene 71.4 257.0
Gasoil / Diesel 73.3 263.9
Residual Oil / Fuel Oil 76.0 273.6
LPG 63.7 229.3
Naphta 73.3 264.0
Petroleum Coke 2021 94.1 338.7
Solid Fuels and Derivatives    
Coal 94.6 340.6
Milled Peat 2021 119.6 430.5
Sod Peat 104.0 374.4
Peat Briquettes 98.9 355.9
Natural Gas 2021 56.4 202.9
Electricity 2021 96.6 347.8

Fuel densities

Conversion from volume (litres) to mass (tonnes) for liquid fuels requires the densities of the liquids, with the most common fuels shown here.

FuelDensity (in litres/tonnes)
Kerosene 1250
Crude Oil 1067
Gasoline (Petrol) 1325
Diesel / Gasoil 1183
Heavy Fuel Oil 1062
LPG* 1915
Biodiesel 1136
Bioethanol 1250
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.

Fuel2021 conversion factor
Aviation fuels 1.1
Biogas / landfill gas 1.0
Coal 1.1
District heat 1.1
Electricity 1.952
Gasoil 1.1
Kerosene 1.1
Light, medium & heavy fuel oils 1.1
LPG 1.1
Manufactured Ovoids 1.2
Marked diesel, road diesel & petrol 1.1
Natural gas


Peat 1.1
Pure biodiesel / bioethanol 1.1
Solar thermal 1.0
Wood briquettes / chips / logs / pellets 1.1