The final energy is the proportion of primary energy that reaches the end consumer after energy conversion and transmission losses. For example, the primary energy coal is converted into electrical energy in the power plant and then supplied to the end consumer as electricity at 230 volts in the socket. This electrical energy is then used by the end consumer for an oven, for example. The electrical current represents the final energy, whereas the thermal energy of the oven is referred to as useful energy. As some of the energy is lost in any form of energy conversion into energy that can no longer be used, the sum of the final energy is less than the sum of the primary energy.