How Hybrids Work | Durham | Croxdale Subaru

How Hybrids Work


Self-charging hybrid vehicles have both an electric motor and a combustion engine. By using both power sources hybrids reduce CO2, NOx and particulate emissions, and make driving more efficient by using less fuel.

e-BOXER, the self-charging hybrid range from Subaru, features a self-charging battery-powered electric motor and an e-BOXER petrol engine in combination. Working together, the engine and motor automatically adjust the hybrid power to achieve the most efficient driving mode depending on your speed and the driving conditions.

Automatically-optimised e-BOXER power

Sometimes just the electric motor powers the car in Electric Vehicle (EV) mode; sometimes the petrol engine alone takes over; and sometimes both the electric motor and the petrol engine deliver power together. Whenever the petrol engine is running, and whenever the car decelerates or brakes, energy is recovered and is used to recharge the battery making it a self-charging hybrid vehicle.

Mild vs. Full vs. Plug-in hybrids

Subaru’s e-BOXER has mild-hybrid technology which automatically controls when the car uses the electric motor alone. This allows the high-voltage battery to remain compact and light. Full hybrid vehicles work in the same way, but also let the driver manually select electric-only drive (called Electric Vehicle – EV mode) if they wish.

Whilst full-hybrid vehicles can travel a limited number of miles using electricity alone, creating no emissions, they also need a larger capacity, heavier battery to do so. For this reason, some self-charging full-hybrids can also use a mains lead from a charging point to charge the battery. These are called Plug-in hybrids.​




Pulling away or driving at slow speeds (up to 15mph) in traffic, the battery-powered electric motor alone drives the car. The petrol engine remains off, using no fuel and creating no emissions. In city traffic, this EV mode offers highly efficient – and completely clean – power to drive.

When cruising, the petrol engine alone is the most efficient power source. The engine also powers the electric generator, recharging the battery.


Under full acceleration or increased load (like climbing a hill) both the petrol engine and electric motor work together providing instant, responsive power. Excess engine power also recharges the battery.

When you decelerate or brake, energy from the car’s movement that would otherwise be lost is captured and used to recharge the battery. This is called regenerative braking


On stopping, the petrol engine switches off to save fuel and reduce emissions. If the battery needs recharging, the engine may keep running so the generator can top it up.