Overall energy efficiency analyses have been made on the electric energy system level. An example of this kind of system analysis is the case, where the current combustion engine based vehichles would be replaced with electric cars.
Limited quantity, uncertain availability and increasing prizes of fossil fuels and the global warming have increased the demands for moving more and more to controlled electric drives having better efficiencies. The popularity of controlled drives has increased along with their improved reliability, efficiency and power capacity, lower prizes and decreased disturbances. Energy efficiency of the electric drives can be increased by raising the nominal voltages, by using more sophisticated converters, by improving their control systems and by cutting their power fluctuations and disturbances.