Series Hybrid Cars: a series design works by powering the vehicle through an electric motor. The batteries supply the power to the motor. As the power arrives at the motor through the battery, series hybrid cars need a substantially larger reserve of power and consequentially a greater amount of batteries need to be carried in the car.

The motor only uses the exact amount of power required for the task in hand. If you spend hours in a traffic jam, you may get a little hot under the collar but your car will not be overheating. An electric motor does not need to tick over or idle when sitting in a jam; it will simply start turning when you start moving. When driving hybrid cars there will be no power (although maybe a little hair) lost even in the most extreme of gridlocks. As the motor will not be working when the vehicle is still, there is no need for the batteries to be recharged until power is again being lost when the car starts to move forward.

The large battery supply that is required for series hybrid cars is kept supplied with energy by a generator that runs from the main gas power unit. This only needs to operate when the batteries are in need of extra power so for much of urban driving there is no need for the motor to operate as only low levels of power are required. This allows the hybrid cars engine to run without emissions for city driving, especially if some higher powered driving, as for highways or main routes is done, and the consequent loss of power means that the hybrid cars batteries are brought upon to their full power supply by the gas motor when out of the urban environment.

There are advantages to both systems, but overall the parallel system is the most flexible for hybrid cars as it allows for the option of either power source to be transferred directly to drive the car without going through another separate means of transmission to the wheels.