Conversion factors
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 content
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. Unless otherwise stated, all values are NCV.
Liquid | toe/t | MJ/kg | MJ/l | Note |
---|---|---|---|---|
Petroleum | ||||
Crude oil | 1.023 | 42.81 | 40.13 | |
Gasoline / petrol (100% petroleum) | 1.065 | 44.59 | 33.03 | |
Kerosene | 1.056 | 44.20 | 35.36 | |
Jet Kerosene | 1.053 | 44.10 | 35.28 | |
Diesel / gasoil (100% petroleum) | 1.034 | 43.31 | 36.61 | |
Residual fuel oil / fuel oil | 0.985 | 41.24 | 39.09 | |
LPG | 1.126 | 47.16 | 24.62 | Assumes 70% propane & 30% butane by mass |
Biofuel / bioliquid | ||||
Bioethanol | 0.633 | 26.49 | 21.20 | |
Biodiesel ME | 0.890 | 37.27 | 32.79 | Methyl ester |
Biodiesel HVO | 1.051 | 44.00 | 37.23 | Hydrotreated vegetable oil |
Biodiesel CHVO | 1.027 | 43.00 | 36.38 | Co-processed hydrotreated vegetable oil |
Biopropane | 1.099 | 46.00 | 24.00 | |
Biojet HVO | 1.051 | 44.00 | 35.20 | Hydrotreated vegetable oil (jet fuel) |
Blended petroleum & biofuel | ||||
Road diesel (avg. biofuel content) | 1.025 | 42.91 | 36.37 | Average diesel-biofuel blend in 2023 (provisional) |
Road petrol (avg. biofuel content) | 1.035 | 43.34 | 32.26 | Average petrol-biofuel blend in 2023 (provisional) |
Solid | toe/t | MJ/kg | Note |
---|---|---|---|
Fossil fuel | |||
Petroleum coke | 0.766 | 32.09 | Updated for 2023 |
Bituminous coal | 0.665 | 27.84 | |
Anthracite | 0.665 | 27.84 | |
Lignite | 0.473 | 19.82 | |
Milled peat | 0.130 | 5.43 | Updated for 2023 |
Sod peat | 0.313 | 13.10 | |
Peat briquettes | 0.443 | 18.55 | |
Biomass | |||
Wood pellets & briquettes | 0.413 | 17.28 | |
Wood logs & chips | 0.313 | 13.11 | Assumes 25% moisture content |
Gas | MJ/m3 | Note |
---|---|---|
Natural gas (GCV) | 39.55 | Gross calorific value for 2023 |
Natural gas (NCV) | 35.67 | Net calorific value for 2023 |
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.
Emission factors for fuels
The table below shows emission factors for CO2 produced from combustion of fuels. Definitions of energy units (kWh) and net calorific values (NCV) appear above. These emission factors include only direct CO2 emissions from combustion of fuels and do not include indirect or upstream emissions, such as those from extraction, cultivation, transportation or processing of fuels.
These emission factors are for statistical purposes, such as calculating direct energy-related emissions on a sectoral and national level. The factors are not suitable for use under frameworks that are based on CO2 equivalent of primary energy or life-cycle emissions: Energy Performance of Buildings Directive (EPBD); BER calculations; Public Sector Monitoring and Report; and greenhouse gas saving criteria under the Renewable Energy Directive. Factors to be used under the EPBD calculation framework are published separately under the BER Calculation methodologies.
SEAI does not currently provide emission factors for CH4 and N2O produced from combustion and recommends consulting the EPA's National Inventory Submissions for details on sector-specific factors for CH4 and N2O.
Values for petroleum coke, milled peat, natural gas and electricity change annually. Unless otherwise stated, all values are calculated based on NCV.
Biomass fuels
The net emission of CO2 from the combustion of biogenic carbon in sustainable biomass fuel (incl. solid biomass, biofuel, bioliquid and biogas) is considered to be zero, as it is assumed that the biomass itself absorbs an equal amount of CO2 during growth as is emitted during combustion. Where biomass fuel is not sustainably produced, CO2 emissions from combustion should be counted. This is consistent with guidelines for greenhouse gas reporting, such as the IPCC 2006 Guideline for National Greeenhouse Gas Inventories & 2019 refinement and EU Emission Trading System.
Liquid | gCO2/kWh | gCO2/MJ | kgCO2/kg | kgCO2/l | Note |
---|---|---|---|---|---|
Petroleum | |||||
Crude oil | 264.0 | 73.33 | 3.140 | 2.943 | |
Gasoline / petrol (100% petroleum) | 251.9 | 69.96 | 3.119 | 2.311 | |
Kerosene | 257.0 | 71.39 | 3.155 | 2.524 | |
Jet Kerosene | 257.0 | 71.39 | 3.148 | 2.519 | |
Diesel / gasoil (100% petroleum) | 263.9 | 73.30 | 3.174 | 2.683 | |
Residual fuel oil / fuel oil | 273.6 | 76.01 | 3.134 | 2.951 | |
LPG | 229.3 | 63.69 | 3.003 | 1.568 | Assumes 70% propane & 30% butane by mass |
Solid | gCO2/kWh | gCO2/MJ | kgCO2/kg | Note |
---|---|---|---|---|
Fossil fuel | ||||
Petroleum coke | 345.0 | 95.83 | 3.075 | Provisional value for 2023 |
Bituminous coal | 340.6 | 94.60 | 2.634 | |
Anthracite | 353.9 | 98.30 | 2.737 | |
Lignite | 363.6 | 101.00 | 2.001 | |
Milled peat | 475.6 | 132.12 | 0.717 | Provisional value for 2023 |
Sod peat | 374.4 | 104.00 | 1.363 | |
Peat briquettes | 355.9 | 98.86 | 1.834 | |
Biomass | ||||
Wood pellets & briquettes | - | - | - | See note above on biomass fuels |
Wood logs & chips | - | - | - | See note above on biomass fuels |
Gas | gCO2/kWh | gCO2/MJ | kgCO2/m3 | Note |
---|---|---|---|---|
Natural gas (GCV) | 184.0 | 51.10 | 2.021 | 2023 values on GCV basis |
Natural gas (NCV) | 204.0 | 56.66 | 2.021 | 2023 values on NCV basis |
Emission factors for electricity
The 'electricity consumption' factor published below includes scope 2 emissions (as defined in GHG Protocol Corporate Accounting and Reporting Standard) from electricity generation, and scope 3 emissions from transmission & distribution losses, and own-use of electricity at plants. SEAI does not currently publish 'well to tank' factors for electricity, which account for scope 3 emissions from extraction, refining and transportation of fuels used for electricity generation.
Electricity 2023 | gCO2/kWh | gCO2/MJ | Note |
---|---|---|---|
Electricity consumption | 254.8 | 70.77 | - 2023 provisional value - CO2 per unit of electricity consumed - Total CO2 from electricity generation / total final consumption of electricity - Use this factor to calculate CO2 for electricity consumption including generation, transmission and distribution losses, and own-use of electricity in power plants (scope 2 and 3 under the GHG Protocol). |
Electricity generation | 229.9 | 63.85 | - 2023 provisional value - CO2 per unit of electricity generated - Total CO2 from electricity generation / gross electricity production (incl. net imports) - Use this factor to calculate CO2 for electricity generation only (scope 2 under the GHG Protocol). |
Fuel densities
Conversion from volume (litres) to mass (tonnes) for liquid fuels requires the densities or specific volumes of the liquids. The most common fuels are shown here.
Liquid | Density [kg/m3] | Specific volume [l/t] | Note |
---|---|---|---|
Petroleum | |||
Crude oil | 937 | 1,067 | |
Gasoline / petrol (100% petroleum) | 741 | 1,350 | |
Kerosene | 800 | 1,250 | |
Jet Kerosene | 800 | 1,250 | |
Diesel / gasoil (100% petroleum) | 845 | 1,183 | |
Residual fuel oil / fuel oil | 942 | 1,062 | |
LPG | 522 | 1,915 | Assumes 70% propane & 30% butane by mass |
Biofuel / bioliquid | |||
Bioethanol | 800 | 1,250 | |
Biodiesel ME | 880 | 1,136 | Methyl ester |
Biodiesel HVO | 846 | 1,182 | Hydrotreated vegetable oil |
Biodiesel CHVO | 846 | 1,182 | Co-processed hydrotreated vegetable oil |
Biopropane | 522 | 1,917 | |
Biojet HVO | 800 | 1,250 | Hydrotreated vegetable oil (jet fuel) |
Blended petroleum & biofuel | |||
Road diesel (avg. biofuel content) | 848 | 1,180 | Average diesel-biofuel blend in 2023 (provisional) |
Road petrol (avg. biofuel content) | 744 | 1,343 | Average petrol-biofuel blend in 2023 (provisional) |
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.
TPER can be calculated by applying primary energy (PE) converion factors, which vary by fuel type, to TFC values. The table below shows the latest PE factors. Historic factors can be found in the SEAI conversion and emission factors spreadsheet. With the exception of the PE factor for electricity, all of the factors below are default values, which provide an approximation of primary energy requirement for each fuel. The PE factor for electricity is calculated based on the primary energy inputs to electrical power generation during the year.
Liquid | PE factor [-] | Note |
---|---|---|
Petroleum | ||
Crude oil | - | |
Gasoline / petrol (100% petroleum) | 1.1 | |
Kerosene | 1.1 | |
Jet Kerosene | 1.1 | |
Diesel / gasoil (100% petroleum) | 1.1 | |
Residual fuel oil / fuel oil | 1.1 | |
LPG | 1.1 | |
Biofuel / bioliquid | ||
Bioethanol | 1.1 | |
Biodiesel ME | 1.1 | Methyl ester |
Biodiesel HVO | 1.1 | Hydrotreated vegetable oil |
Biodiesel CHVO | 1.1 | Co-processed hydrotreated vegetable oil |
Biopropane | 1.1 | |
Biojet HVO | 1.1 | Hydrotreated vegetable oil (jet fuel) |
Blended petroleum & biofuel | ||
Road diesel (avg. biofuel content) | 1.1 | |
Road petrol (avg. biofuel content) | 1.1 |
Solid | PE factor [-] | Note |
---|---|---|
Fossil fuel | ||
Petroleum coke | 1.1 | |
Bituminous coal | 1.1 | |
Anthracite | 1.1 | |
Lignite | 1.1 | |
Milled peat | 1.1 | |
Sod peat | 1.1 | |
Peat briquettes | 1.1 | |
Biomass | ||
Wood pellets & briquettes | 1.1 | |
Wood logs & chips | 1.1 |
Electricity 2023 | PE factor [-] | Note |
---|---|---|
Electricity consumption | 1.888 | - 2023 provisional value - Primary energy input per unit of available final energy consumption. - Electricity imports are not included in the calculation of this factor. |
Electricity generation | 1.706 | - 2023 provisional value - Primary energy input per unit of electricity generated, before subtracting own use of electricity in power plants, and transmission & distribution losses. - Electricity imports are not included in the calculation of this factor. |