High speed trains run on electricity instead of diesel fuel. Because much of the world's electricity is still generated at fossil fuel burning power plants, high speed trains do contribute to carbon emissions, however the climate impact of one train is significantly less than that of many personal vehicles.

Bullet trains, or high-speed rail (HSR) systems like the Japanese Shinkansen or the French TGV, do not run on liquid fuels like diesel or gasoline in the traditional sense. Instead, they are powered entirely by electricity. This power is typically delivered through an overhead line system known as a catenary, where a pantograph on top of the train maintains constant contact with the wires to draw current. This electrical energy is then converted by onboard traction motors into mechanical motion. Because they rely on the electrical grid, bullet trains are considered much more environmentally friendly than planes or cars, especially if the local grid is powered by renewable sources like wind, solar, or nuclear energy. This electric propulsion allows for the rapid acceleration and sustained high speeds (often exceeding 300 km/h) that define the "bullet" experience.