Hi - easy one, it's the BFC effect - big friendly cables

. I've forgotten the proper number now, but I'm going to say that for every kW you use at home 2kW is produced at the power station, ie half the energy is lost as heat on its way to you in cables and transformers etc. Also, the supply voltage at your house will drop as you increase the current draw. Hopefully not enough that you will notice flickering lights etc but it can be readily seen with test instruments. This is the end result of losses in transmission that means we can never get more useable energy out than is put in. Hope that helps. Cheers, David.