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Fuel energy density comparison: CNG, ANG, LNG, hydrogen and diesel
Per kilogram, hydrogen wins by a wide margin. Per liter, the order turns upside down. Switch the view to see both.
Energy stored in the fuel
The numbers behind the chart
| Fuel | Storage condition | MJ per kg | MJ per liter | CO₂ at use, g/MJ |
|---|---|---|---|---|
| Diesel | liquid, ambient | 43.0 | 35.8 | 74.1 |
| Gasoline | liquid, ambient | 43.4 | 32.3 | 69.3 |
| LNG | −162 °C, near 1 bar | 50.0 | 21.1 | 56.1 |
| CNG, 250 bar | 15 °C | 50.0 | 10.0 | 56.1 |
| CNG, 200 bar | 15 °C | 50.0 | 8.4 | 56.1 |
| Liquid hydrogen | −253 °C | 120.0 | 8.5 | 0.0 |
| ANG, 35 bar, 150 V/V | 15 °C, carbon adsorbent | 50.0 | 5.1 | 56.1 |
| Hydrogen, 700 bar | 15 °C | 120.0 | 4.8 | 0.0 |
| Hydrogen, 350 bar | 15 °C | 120.0 | 2.9 | 0.0 |
What the comparison says
Liquid fuels set a high bar. A liter of diesel holds about 36 megajoules and needs nothing more than a thin steel tank. Every gaseous fuel has to be made dense before it competes, and the chart shows how far each method gets. Liquefying methane reaches about 60 percent of diesel per liter, which is why LNG trucks cover long-haul routes that CNG struggles with. Compression to 250 bar reaches a little under 30 percent, enough for buses and delivery fleets that return to a depot each night.
Hydrogen flips the picture. Its 120 megajoules per kilogram are almost three times diesel's, but a liter of tank at 700 bar holds under 5 megajoules, about 13 percent of diesel. That gap is the whole subject of hydrogen storage research, and it explains why fuel-cell cars carry large carbon-fiber tanks for 5 to 6 kilograms of fuel.
The adsorbed natural gas row sits below CNG per liter at a seventh of the pressure. The trade is in the hardware, lower-pressure compression and tanks, as the ANG guide explains.
Carbon at the point of use
Burning natural gas releases about 56 grams of CO₂ per megajoule, against about 74 for diesel. That is a tailpipe or flue figure only. Methane that leaks before it is burned is a strong greenhouse gas, and the full picture is covered in is natural gas clean.
Questions about energy density
Which fuel has the most energy per liter?
Of the fuels compared, diesel carries the most energy per liter, about 36 MJ. LNG reaches about 60 percent of that, CNG at 250 bar about 28 percent and hydrogen at 700 bar about 13 percent.
Why does hydrogen look best per kilogram but worst per liter?
Hydrogen holds about 120 MJ per kilogram, nearly three times diesel, but it is so light that even at 700 bar a liter of tank holds only about 40 grams of it.
Do these numbers include the tank?
No. They describe the fuel inside the vessel. Pressure vessels and cryogenic tanks add a great deal of mass and some volume, which is why system-level figures are lower.
Why is CO₂ zero for hydrogen?
Burning or converting hydrogen releases no carbon dioxide at the point of use. Emissions from producing the hydrogen depend entirely on how it was made and are not shown here.