With new technologies come new modes of calculation. Human beings, naturally reluctant to change, we often seek to compare with what we know to better to better understand the impact of something new on our daily lives. When electric vehicles first appeared, the first question asked was: “How does this compare with our our internal combustion vehicles, and how can I calculate the potential savings potential savings? Thus was born the concept of litre-equivalent (L-e). This measure makes it possible compare the energy efficiency of an electric vehicle with that of a fuel-powered vehicle. But how is it calculated, and what exactly is it used for?
WHAT IS L-É?
At first glance, you might think that the “é” stands for “electric”, but in reality it means “equivalent”. The litre-equivalent represents the energy equivalence in liters of fuel (usually gasoline) that a gasoline-powered vehicle would consume for the same distance covered. This measure can also be applied to hydrogen-powered vehicles, natural gas or other energy technologies.
Energy is measured in joules. Whether it's the explosion in an engine cylinder or the electricity
propelling a vehicle, both generate energy, expressed in joules. Here's the energy equivalence of different fuels and energies:
| Fuel/Energy |
Energy per unit |
Equivalence in kWh |
| Gasoline |
34,2 MJ per liter |
9,5 kWh |
| Diesel |
38,6 MJ per liter |
10,7 kWh |
| Hydrogen |
120 MJ per kg |
33,3 kWh |
| Natural gas (CNG) |
38,3 MJ per m³ |
10,6 kWh |
| Electricity (1 Watt) |
1 joule per second |
1 kWh = 3,6 MJ |
Notes :
- Natural gas (CNG): 1 m³ of compressed natural gas (CNG) contains approx. 38.3 MJ, i.e. approximately 10.6 kWh.
- Hydrogen: 1 kg of hydrogen contains around 120 MJ, or 33.3 kWh.
- Gasoline and diesel: These are standard values commonly used to compare these fuels with other energy sources.
- Electricity: 1 kWh corresponds to 3.6 MJ of energy.
Regardless of the energy source used, the L-value provides a universal basis for comparison to assess energy requirements on the same reference basis.
WHEN AND WHY IS L-É USED?
Looking ahead to the future of transport, I see a world where fleets will be multi-energy, with vehicles running on hydrogen, natural gas, electricity and other technologies still to come. At AttriX, we advocate an approach based on the right vehicle for the right need.
This marks a major paradigm shift. We're used to standardized solutions, facilitating management and procurement. However, the transition to energy-efficient solutions requires a complete overhaul of the business model. To succeed transformation, we need the right tools, and the emergence of various technologies in the transportation sector.
In a mixed fleet, it's crucial to have a baseline against which to compare vehicles on standard and universal criteria, such as fuel efficiency. The L-é is therefore not to compare running costs directly, but rather to assess fuel efficiency. This data can help to better plan future vehicle deployments and ensure that each vehicle is adapted to specific needs.
IN SUMMARY
The concept of litre-equivalent is useful in certain situations, but in everyday business it's not the data that will be used most. What counts above all are costs, not just energy efficiency. Personally, I use more consumption indicators such as kWh/100 km, as they enable me to calculate savings more based on data I already know, with associated costs.
Consider the following example:
- A diesel vehicle consuming 35 L/100 km at $1.70/liter will cost $59.50 per 100 km.
- The equivalent for an electric vehicle consuming 140 kWh/100 km with an L-e of 13.08 L-e/100 km will cost $21 per 100 km, at a rate of $0.15/kWh.
The difference in L-e is impressive, but what speaks louder is the difference in price per 100 km. Some will point out that we haven't included the cost of recharging in the calculation. But that's a bit like not including the cost of filling stations in the calculation for diesel vehicles. That, however, is another debate!
