Fuel energy content: kWh, MJ and CO₂ per litre, kg or m³

How this fuel energy calculator works

Choose a fuel, enter a quantity in its usual unit (litres, kilograms or cubic metres) and pick the heating-value basis. The calculator returns the energy in kWh, MJ and BTU, the CO₂ released on combustion and, from the price you pay, what each kWh really costs — both as fuel and as useful heat or work after the efficiency of your boiler, engine or power plant.

It covers 21 fuels: road and heating oils, kerosene, heavy fuel oil, LPG, pipeline and compressed natural gas, four coal grades and coke, firewood and pellets, hydrogen, ethanol, biodiesel, and three uranium cases. Two charts compare the energy per unit and the CO₂ per kWh of every combustible fuel, splitting fossil from biogenic CO₂.

The formulas

Net calorific values and CO₂ factors are IPCC 2006 defaults (e.g. diesel 43.0 MJ/kg and 74.1 kg CO₂/GJ; natural gas 56.1 kg/GJ; bituminous coal 25.8 MJ/kg and 94.6 kg/GJ).

Worked example: 100 litres of diesel

The default is 100 L of diesel at 1.60 per litre, on a net basis:

• Energy: 100 × 35.9 MJ ÷ 3.6 = 997 kWh (3,590 MJ; gross value 1,058 kWh)
• CO₂: 100 × 0.0359 GJ × 74.1 kg/GJ = 266 kg (2.66 kg per litre, 267 g per kWh)
• Cost per kWh of fuel: 1.60 ÷ 9.97 = 0.160

In a car engine converting about 30% of that into motion, each useful kWh costs over 0.50, compared with 0.25 or less for an electric motor running on grid electricity at 90% efficiency.

Energy content of common fuels

How to read the results

• LHV vs HHV: compare like with like. A condensing boiler can exceed 100% “efficiency” on an LHV basis because it recovers latent heat, so enter efficiencies on the same basis as the heating value.
• CO₂ per kWh shows why switching from coal (340–385 g) to gas (≈200 g) halves emissions per unit of heat, and why biomass CO₂ is only “neutral” if forests regrow.
• Cost per useful kWh is the number to compare against electricity or a heat pump (whose useful heat costs electricity price ÷ COP).

Tips

1. Check your fuel’s real calorific value on delivery notes or gas bills; coal and wood vary most.
2. Dry your firewood. Wood at 50% moisture delivers about 2 kWh/kg versus 4 kWh/kg when air-dried to 20%.
3. Compare fuels per useful kWh, not per litre or kilogram. The heating cost comparison does this for boilers and heat pumps.
4. Convert units with the energy unit converter and prices with the energy price converter.

Limitations

Values are IPCC defaults and typical densities; commercial fuels vary with season, blend and origin (±3% for oil products, ±10% for coal, ±20% for wood). CO₂ figures cover combustion only unless the upstream option is ticked, in which case rough well-to-tank factors are added. Methane slip, nitrous oxide and black carbon are not included. Uranium energy depends strongly on reactor type, enrichment and burn-up; the figures are indicative thermal energy.

Method & assumptions

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