Alternators installed in cars produce Electricity known as Direct current (DC) at 13.2-14.9 volts. The alternators are rated by the amperage they can produce. The more amperage the more "stuff" you can have running in your car. The manufacture determines the size by what is installed in the car. If you buy a car with lots of extra electrical gadgets the amp rating on your battery and alternator will normally be larger.
Your definition of electricity is unknown by us, so it is hard to answer. What are your concerns about?