The National Grid is the network of cables that covers the      whole country to take electricity from the power station to      homes and factories.    Electricity is generated in the power stations but cannot be      transmitted to houses just yet as the current would be too      high (energy will be lost as heat from the cables).   The solution is to use a step up transformer that steps up the      voltage to a very high value (thousands of volts). This      makes the current smaller, minimizing the heat loss.   For the electricity to reach homes at the appropriate voltage,      a step down transformer is used, this lowers the voltage      from its very high value (thousands of volts) to a lower value      (230 volts for homes).     Electrical power = current x voltage        P = I x V       Power is measured in Watt: W.