The distribution system loses (as heat) about 8% of the energy that is supplied to it - i.e. it is 92% efficient. The generation system is less efficient. A conventional power station is about 35% efficient although modern combined heat and power (CHP) plants can have efficiencies approaching 60%. Most of the losses in the power station are inherent in the thermodynamic processes with the generators being about 92% efficient.
So, by the time we use the electricity, it only represents about 33% of the original energy content of the fuel. There is then a further loss in the appliance that we use. For a standard motor, this would be about 12%, making the whole system about 28% efficient.
If we can improve efficiency, then this reduces the cost, the environmental impact and the rate at which we are using up precious fossil fuel reserves. Efficiency can be thought of as the third fuel an alternative to alternative energy sources.