System combined power refers to the sum of power outputs from two or more drivetrains that can operate simultaneously in a hybrid vehicle. It is the sum of the power output from the electric motor and the internal combustion engine. However, the combined power is not merely the addition of their maximum outputs but is determined based on the maximum power integrated from both systems.
According to the documents from the International Energy Agency (IEA), a vehicle is termed as a hybrid vehicle if it possesses the following characteristics related to the "Energy & Power Transfer Routes":
1：The energy propelling the vehicle's wheels comes from at least two different energy conversion devices (e.g., internal combustion engines, gas turbines, Stirling engines, electric motors, hydraulic motors, and fuel cells).
2：These energy conversion devices draw energy from at least two different energy storage devices (e.g., fuel tanks, batteries, flywheels, supercapacitors, and high-pressure hydrogen storage tanks).
3：Among the paths flowing from the energy storage to the wheels, at least one is reversible.
In the automotive domain, power units include kW, Ps, hp, etc., which commonly refer to kilowatts and horsepower. While kilowatts are international units – with one kilowatt denoting an engine performing one thousand joules of work in one second, horsepower is an imperial unit. Horsepower further branches into metric horsepower (Ps) and mechanical horsepower (hp). Metric horsepower denotes the work done when a horse raises 75 kilograms of water by 1 meter in one second, while mechanical horsepower refers to a horse lifting 1000 pounds by 33 feet in one minute. This analogy was later used to describe engine power.
