The electrical loads of present automobiles are related to multimedia, HVAC (heating, ventilation, air conditioning), body electronics (power windows, heated backlight) and lighting (exterior, interior). Their consumption is above 3 kW.

A conventional vehicle with internal combustion engine uses part of the mechanical power (about 5 kW) to drive the mentioned on-board equipments through the alternator, considering its efficiency of approximately 60%. Regarding cabin heating, engine waste heat assures the cabin thermal comfort that requires 5-10 kW, while a mechanically driven vapour compression cycle guarantees the cabin cooling in summer, absorbing up to 3 kW electric and generating up to 5 kW of cooling power.

On a fully electric vehicle (FEV), electrical auxiliaries are supplied by the batteries pack resulting in increased mass installed to guarantee reasonable covered ranges from 50 to 100 km. The power consumption of any kind of auxiliary contributes reduces this range and decreases the battery lifetime. Moreover, the amount of heat available for cabin heating is very small (less than 5 kW) and the energy available to supply an air conditioning system is far low than normally required by a conventional one.