Fuel Energy Content Comparison Calculator
Compare jet fuel, SAF, liquid hydrogen, and batteries by the two numbers that decide what can fly: energy per kilogram and energy per litre.
Why jet fuel has been so hard to replace
An aircraft is unusually demanding of its fuel: it must carry the energy for hours, lift its own weight, and fit it inside a slender airframe. Kerosene is remarkable because it is strong on both weight and volume at once. Every alternative trades one for the other — hydrogen wins on weight but loses badly on volume; batteries lose on both — which is what this comparison makes visible.
Once you can see the energy each carrier stores, the Hydrogen / Battery Aviation Range calculator turns those figures into estimated flight range.
Frequently Asked Questions
What is the difference between energy per kg and energy per litre?
Energy per kilogram (gravimetric, or specific energy) is how much energy a carrier stores for each unit of weight — it matters because an aircraft has to lift its fuel. Energy per litre (volumetric energy density) is how much it stores per unit of space — it matters because the fuel has to fit inside the tanks. A good aviation fuel needs to be strong on both, and jet kerosene happens to be excellent at each, which is why it has been so hard to replace.
Why is hydrogen described as high energy but hard to use?
Liquid hydrogen holds roughly 120 MJ per kilogram — nearly three times Jet A — so by weight it is the best chemical fuel there is. But even as a cryogenic liquid it is extremely light and bulky, storing only about 8.5 MJ per litre, roughly a quarter of Jet A. A hydrogen aircraft therefore needs far larger, heavier, insulated tanks, which is the central engineering challenge of hydrogen flight.
Why can't batteries power large airliners?
A modern lithium-ion pack stores on the order of 0.9 MJ per kilogram — about 250 watt-hours per kilogram — which is roughly 45 to 50 times less energy per kilogram than jet fuel. Even after accounting for an electric drivetrain's much higher efficiency, the sheer weight of batteries needed for a long flight is prohibitive, which is why battery-electric aviation is aimed at small aircraft and short hops.
Is SAF more energetic than ordinary jet fuel?
Marginally. Many sustainable aviation fuels are slightly higher in specific energy — around 44 MJ per kilogram versus about 43 for Jet A — because they can be richer in hydrogen and lower in aromatics. In practice the energy content is close enough that SAF is a genuine drop-in replacement; its advantage is environmental, not energetic.
Educational estimate only. Uses representative values; real specific energy and density vary by fuel grade, battery chemistry, and storage conditions.