Fuel Energy Content
Comparing Gasoline, Diesel, and Other Fuels
Compare FuelsWhy does a diesel truck get better mileage than a gasoline one? Why do electric cars use "MPGe" instead of MPG? The answer lies in energy content—different fuels pack different amounts of energy per gallon, pound, or cubic foot. Understanding fuel energy content helps compare vehicles, heating systems, and energy costs.
Liquid Fuels Energy Content
| Fuel | BTU/Gallon | MJ/Liter | kWh/Gallon |
|---|---|---|---|
| Gasoline (regular) | 120,286 | 34.2 | 33.4 |
| Gasoline (premium) | 121,463 | 34.5 | 33.7 |
| Diesel (#2) | 137,381 | 38.6 | 38.2 |
| Biodiesel (B100) | 126,206 | 35.7 | 37.0 |
| Ethanol (E100) | 84,530 | 23.4 | 24.8 |
| E85 (85% ethanol) | 90,660 | 25.6 | 26.6 |
| Propane (LPG) | 91,502 | 25.4 | 26.8 |
| Heating oil | 138,500 | 38.7 | 40.6 |
| Jet fuel (Jet A) | 128,100 | 35.0 | 37.5 |
Gaseous Fuels Energy Content
| Fuel | BTU/Unit | MJ/Unit | kWh/Unit |
|---|---|---|---|
| Natural gas (per therm) | 100,000 | 105.5 | 29.3 |
| Natural gas (per CCF) | 103,000 | 108.7 | 30.2 |
| Natural gas (per cubic ft) | 1,030 | 1.09 | 0.302 |
| Propane (per gallon) | 91,502 | 96.5 | 26.8 |
| Hydrogen (per kg) | 134,000 | 141.4 | 39.3 |
| Compressed natural gas (GGE)* | 120,000 | 126.6 | 35.2 |
*GGE = Gasoline Gallon Equivalent
Solid Fuels Energy Content
| Fuel | BTU/lb | MJ/kg | kWh/kg |
|---|---|---|---|
| Anthracite coal | 12,000-13,000 | 30-32 | 8.3-8.9 |
| Bituminous coal | 10,500-12,500 | 26-31 | 7.2-8.6 |
| Sub-bituminous coal | 8,000-10,000 | 20-25 | 5.6-6.9 |
| Lignite | 5,000-7,000 | 12-17 | 3.3-4.7 |
| Wood (air dried) | 6,400 | 15 | 4.2 |
| Wood pellets | 8,000 | 18.6 | 5.2 |
Why Energy Content Matters
Vehicle Fuel Efficiency
A diesel vehicle getting 35 MPG actually travels further per BTU than a gasoline car at 30 MPG:
- Diesel: 35 miles ÷ 137,381 BTU = 0.000255 miles/BTU
- Gasoline: 30 miles ÷ 120,286 BTU = 0.000249 miles/BTU
The diesel is 2.4% more efficient per unit of energy, not just per gallon.
Heating Cost Comparison
To deliver 1 million BTU of heat:
| Fuel | Amount Needed | Cost* |
|---|---|---|
| Natural gas | 10 therms | ~$12 |
| Propane | 10.9 gallons | ~$33 |
| Heating oil | 7.2 gallons | ~$29 |
| Electricity | 293 kWh | ~$35 |
*Approximate 2024 prices, varies by region
Energy Density Comparison
Energy density (energy per unit weight) affects what fuels are practical for different uses:
| Fuel | MJ/kg | Use Case |
|---|---|---|
| Hydrogen | 142 | Highest by weight; hard to store |
| Gasoline | 46 | Cars, aircraft |
| Diesel | 45 | Trucks, ships, generators |
| Jet fuel | 43 | Aircraft |
| Natural gas | 55 | Heating, power plants |
| Lithium battery | 0.5-1 | EVs (low energy density) |
Batteries store ~50× less energy per kg than gasoline—why EVs need heavy battery packs.
Converting Between Fuels
Gasoline Gallon Equivalents (GGE)
| Fuel | Amount = 1 GGE |
|---|---|
| Gasoline | 1 gallon |
| Diesel | 0.88 gallons |
| Ethanol (E100) | 1.42 gallons |
| E85 | 1.33 gallons |
| Propane | 1.31 gallons |
| Natural gas | 126.67 cubic feet |
| Electricity | 33.7 kWh |
Conclusion
Different fuels contain vastly different amounts of energy. Diesel packs about 14% more energy per gallon than gasoline; ethanol has about 30% less. Understanding these differences helps you compare fuel costs, vehicle efficiency, and heating options on an equal energy basis rather than just price per gallon.