Quote:
Originally Posted by villiom
hyrid car runs on electric power at low speeds...
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That isn't necessarily the case. Some CAN run on electric only, but generally the electric motor assists the engine when the car accelerates. It takes much more power to do that than to drive at a steady speed, so a hybrid can have a smaller engine that is more economical to run at cruising speed. Normal cars have to have oversized engines to give power to accelerate, so they are inefficient at cruising speed. (This is something called Base Specific Fuel Consumption, or BSFC, which you can look up.)
The power for the hybrid mostly comes from braking: the electric motor acts as a generator, putting power back into the batteries. In addition, if the battery drops too low, the engine will recharge it.
See for instance here for more info:
HowStuffWorks "How Hybrid Cars Work"