In the 1990s the European Automobile Manufacturers Association entered into a voluntary agreement with the European Commission to reduce CO2 emissions per kilometer.

Most regulations focus on CO2 emissions measured in grams per kilometer emitted from the vehicle [...].

Fuel Economy – A measure of the distance a vehicle can travel on a set amount of fuel, measured in miles per gallon (MPG) in the U.S., and liters per 100 kilometers in Europe and China.

kW – Kilowatt – A unit of electrical power equal to 1,000 Watts.

Energy capacity is measured in kilowatt hours (1 kWh is equivalent to 1 kilowatt provided for 1 hour).

The rate of energy transfer is measured in kilowatts (kW) for automotive applications and typically portrayed as power density (W/kg) for batteries.