Hybrid power units combine at least two different methods of generating power.
The hybrid power units in cars typically use a petrol engine together with an electric motor and batteries. The Toyota Prius is one of the best-known hybrid electric vehicles and can use its engines singly or in parallel. At low speeds – up to 15mph – it uses the electric motor but as the driver asks for more power the petrol engine will fire up and assist. The petrol engine can also be used to generate electricity that can be stored in the car's batteries. Electricity can also be produced regeneratively when braking.
All the electricity used by the Toyota Prius is self-generated. It never needs to be plugged in for a recharge.
Hybrid power units are used for two reasons: to reduce emissions and to reduce consumption of fossil fuels, such as petrol or diesel. Both are achieved by reducing the running time of the petrol or diesel engine versus a conventional-engined car.
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