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 unit conversion

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.

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, electricity, and blended petroleum & biofuel 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.

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.

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.

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.