To provide useful information that allows consumers to make informed choices about the relative convenience of different fuels and, in particular, to enable a comparison between traditional fuels and so-called alternative or sustainable fuels, European legislation requires, for information purposes, the publication and dissemination of comparisons between the comparable average unit prices of fuels and of information on the energy equivalence factors of fuels.
The principle of energy equivalence
Energy equivalence is based on a physico-chemical value called the net calorific value (NCV), which is needed to compare traditional liquid fuels (petrol and diesel) with gaseous fuels at atmospheric pressure (LPG and methane), as well as with those used in electric and hydrogen engines.
The NCV measures the amount of energy released when a fuel is burned, and so makes it possible to compare very different energy sources.
In this case, the price comparison does not take vehicle efficiency into account, only the intrinsic characteristics of the fuels.
How to compare the prices of different fuels?
Consumers can compare different fuels by dividing the price of the fuel, expressed in €/litre (or in €/kg for methane), by the coefficient expressing the corresponding energy content, which gives the price per megajoule (€/MJ) or the price in euros per kilowatt-hour (€/kWh).
This makes it possible to compare unit prices, regardless of the fuel’s unit of measurement or differences in calorific value.
The table below shows the equivalence factors for the main fuels.
Energy content of fuels
| Fuel | Energy content (MJ) – net calorific value | Energy content (kWh) – net calorific value |
| Unleaded petrol (SP95 / SP98) | 32 MJ/L | 8.89 kWh/L |
| Fossil diesel (B7) | 36 MJ/L | 10.00 kWh/L |
| E85 (average) | 25 MJ/L | 6.94 kWh/L |
| Biodiesel (methyl ester) | 33 MJ/L | 9.17 kWh/L |
| Biodiesel (ethyl ester) | 34 MJ/L | 9.44 kWh/L |
| Bioethanol (from biomass) | 21 MJ/L | 5.83 kWh/L |
| Liquefied petroleum gas (LPG) | 24 MJ/L | 6.67 kWh/L |
| Compressed natural gas (CNG) | 48 MJ/kg | 13.33 kWh/kg |
| Liquefied natural gas (LNG) | 49 MJ/kg | 13.61 kWh/kg |
| Biogas | 50 MJ/kg | 13.89 kWh/kg |
| Hydrogen gas (H₂) | 120 MJ/kg | 33.33 kWh/kg |
| NGV (natural gas vehicle) | — | ≈ 9.97 kWh/Nm³ |
| ED95 fuel | 21 MJ/L | 5.83 kWh/L |
| Electricity | 3.559 MJ/kWh | 1.00 kWh |
Conversion: 1 MJ = 0.2778 kWh (net calorific value). Values may vary slightly depending on temperature, pressure and the composition of the product.
Why the energy equivalence of fuels matters
Knowing the energy equivalence of fuels is useful not only for comparing prices at the pump, but also for assessing the environmental and economic performance of the energy sources available.
For example:
- one litre of diesel contains about 10 kWh of energy, almost twice as much as E85;
- one kilogram of hydrogen provides nearly 33 kWh, but requires specific storage and conversion;
- electricity, for its part, stands out for a much higher efficiency in electric motors.
These differences explain the gaps in consumption between engine types and justify the need for a standardised indicator such as the energy equivalence of fuels.
Official sources and regulatory references:
The equivalence factors shown are taken from the following official sources:
- Directive (EU) 2018/2001 of the European Parliament and of the Council of 11 December 2018 on the promotion of the use of energy from renewable sources,
- Directive (EU) 2023/2413 of the European Parliament and of the Council of 18 October 2023 amending Directive (EU) 2018/2001
- French Ordinance No 2011-1105 of 14 September 2011 transposing Directives 2009/28/EC and 2009/30/EC of the European Parliament and of the Council of 23 April 2009 in the field of renewable energy and biofuels
- The French order of 2 May 2012, as amended, on the energy content of biofuels and fuels.