What Powers a Car?

A car is powered by energy stored in fuel or batteries—most commonly gasoline or diesel, increasingly electricity, and sometimes hydrogen or alternative fuels—which the powertrain converts into motion via an engine or electric motor. In practical terms, that energy source feeds a system of components that turn stored energy into rotational force at the wheels, moving the vehicle down the road.

How Cars Turn Energy Into Motion

Regardless of what’s in the tank or battery, the basic idea is the same: store energy, convert it into mechanical power, then transmit that power to the wheels. Internal-combustion vehicles burn fuel to drive pistons and a crankshaft; electric vehicles use current from a battery to spin one or more motors. Hybrids blend both approaches, switching or combining power sources for efficiency and performance.

Key Powertrain Components

The following lists outline the major components that enable energy conversion and motion in common vehicle types. Understanding these pieces helps explain how different energy sources ultimately produce the same result: forward motion.

• Internal-combustion engine (ICE): Burns gasoline or diesel to create pressure that turns a crankshaft.
• Fuel system: Tank, pump, and injectors deliver fuel to the engine.
• Exhaust and emissions control: Catalytic converters and filters reduce pollutants.
• Transmission and differential: Adjust torque and speed before power reaches the wheels.
• Electric motor(s): In EVs and hybrids, convert electrical energy into rotational motion.
• Battery pack: Stores electrical energy; in hybrids, smaller; in EVs, large high-voltage packs.
• Inverter/charger: Manages current flow between battery, motor, and grid (for plug-ins).
• Regenerative braking: Recovers kinetic energy back into the battery during deceleration.

While layouts vary, these components work together to balance power, efficiency, and drivability, whether the car burns fuel, draws from a battery, or does both.

Internal Combustion Power

Gasoline engines use spark ignition; diesel engines use compression ignition. Both create controlled explosions that drive pistons. Modern engines employ turbocharging, direct injection, and variable valve timing to boost power and efficiency. They are quick to refuel and supported by a mature infrastructure, but tailpipe emissions include CO₂ and pollutants, which are mitigated by advanced aftertreatment systems.

Electric Power

Battery-electric vehicles (EVs) use one or more electric motors powered by a high-voltage battery. An inverter modulates current, and regenerative braking recaptures energy. EVs have no tailpipe emissions, deliver instant torque, and require less maintenance. Their environmental impact depends on the electricity generation mix, and practical range and charging speed vary by model and network availability.

Hybrid Systems

Hybrids (HEVs) and plug-in hybrids (PHEVs) combine an engine with an electric motor and battery. Series hybrids use the engine mainly as a generator; parallel hybrids let the engine and motor drive the wheels; many systems blend both. PHEVs can drive on electricity for short trips and switch to fuel for longer journeys, reducing fuel use without full reliance on charging networks.

Hydrogen Fuel Cells

Fuel-cell electric vehicles (FCEVs) generate electricity onboard by combining hydrogen with oxygen in a fuel-cell stack, emitting only water vapor at the tailpipe. They refuel quickly but depend on limited hydrogen infrastructure and the carbon intensity of hydrogen production, which today largely comes from natural gas unless produced via low-carbon electrolysis.

Primary Energy Sources Used in Cars

From conventional fuels to cutting-edge alternatives, these are the main energy sources that power cars today, each with distinct strengths, limitations, and infrastructure needs.

• Gasoline: The dominant fuel for light-duty cars; high energy density and widespread availability.
• Diesel: Higher efficiency and torque; common in trucks and some SUVs; requires advanced emissions controls.
• Electricity (batteries): Powers EVs and PHEVs; zero tailpipe emissions; performance depends on charging access and grid mix.
• Hydrogen: Used in FCEVs to produce electricity onboard; fast refueling; limited station network.
• Ethanol (E10–E85): Biofuel blended with gasoline; reduces petroleum use; energy content and availability vary by blend.
• Biodiesel (B5–B20, B100): Renewable diesel substitute for compression-ignition engines; cold-weather and warranty considerations apply.
• Compressed/Liquefied Natural Gas (CNG/LNG): Lower CO₂ per unit energy than gasoline; niche light-duty use, more common in fleets.
• Liquefied Petroleum Gas (LPG/Propane): Alternative spark-ignition fuel with lower emissions than gasoline; regional availability.
• Solar (assist): Solar panels can supplement accessories or trickle-charge batteries; currently insufficient alone for primary propulsion in consumer cars.

The right energy source depends on use case, cost, policy incentives, and regional infrastructure, with many markets now supporting multiple paths side by side.

Where the Power Ultimately Comes From

A car’s “power” is the immediate energy source at the vehicle, but the climate impact depends on well-to-wheel factors: how fuel is extracted, produced, and delivered, or how electricity and hydrogen are generated. Cleaner grids and low-carbon hydrogen improve the lifecycle footprint of EVs and FCEVs, while sustainable biofuels can cut emissions from combustion engines where electrification is less practical.

Efficiency and Emissions at a Glance

The following points summarize how different power sources typically compare on efficiency and emissions at the vehicle and system level.

1. EVs: Highest drivetrain efficiency and zero tailpipe emissions; lifecycle emissions depend on grid mix and battery production.
2. Hybrids/PHEVs: Lower fuel consumption than conventional ICEs; PHEVs can run emissions-free locally when charged.
3. Efficient ICEs: Improvements like turbocharging and start-stop reduce fuel use, but tailpipe CO₂ remains inherent to combustion.
4. Fuel cells: Zero tailpipe emissions; lifecycle impact hinges on hydrogen production pathway.
5. Biofuels and gaseous fuels: Can reduce net CO₂ and some pollutants, with trade-offs in energy content, availability, and infrastructure.

Real-world results vary with driving style, climate, vehicle size, and energy sourcing, making local conditions and usage patterns key to choosing a powertrain.

Summary

A car is powered by stored energy—most often gasoline or diesel, increasingly electricity, and sometimes hydrogen or other alternative fuels—that the powertrain converts into motion. Internal-combustion engines, electric motors, hybrids, and fuel cells represent different ways to perform the same job, with distinct trade-offs in cost, convenience, efficiency, and emissions shaped by local infrastructure and energy supplies.