There are several hybrid engine designs, but they all combine gas and electric power. A car requires the most power during acceleration or on a steep hill, but can otherwise function quite well on a small engine. The electric power in a hybrid engine gives the gas engine a boost when additional power is needed. Because hybrid cars have the electric component, they can carry a smaller, more efficient engine than a comparable non-hybrid car. Smaller engines use less energy.

There are two main types of hybrid cars: series hybrid cars and parallel hybrid cars.

Parallel hybrid cars work by using a combination of a traditional gas engine and a high output electric motor. The different elements of the engine start working at higher or lower levels of output are required. If the car is being driven carefully and accelerating at a reasonable level the electric motor will work on its own until a greater output is needed at a higher speed. Then the small high performances, in terms of fuel economy that is, gas engine takes over. This is a seamless almost unnoticeable process with a smooth transition of control from electric to gas power.

As the acceleration is powered by the electric motor the gas engine can be much smaller and more economical. There is no need for a great deal of energy, merely enough to keep the car at a steady speed, or to move the car from a mid range, around 40 mph to a higher speed. This requires a lot less energy than the initial movement from a standstill and consequently can be achieved with a lower level of power.

The parallel system of using both the gas engine and electric motor for hybrid cars means that there is less loss of power as when the car is traveling at higher speeds. As the energy is not required to go through the batteries and electric motor before providing power to the car. When traveling in this mode there is no need for the electric motor to operate and this also allows it to be recharged by the gas engine as the vehicle is traveling along. All ready for when the hybrid car slows and switches back to the electric motor.

The hybrid car is designed to give drivers the same convenience as any other car. You can drive it long distances, accelerate quickly and there is no recharging time involved. In fact, until you look under the hood, you might not even realize you're in a hybrid car.