Economically, it means that Sainsburys pay a little less for electricity, and all the cars going into the car park burn a little more fuel instead – thus shifting the cost from the supermarket to their customers.

Environmentally it’s even worse – I am sure that getting electricity from petrol via cars’ movement with this system will be far less efficient than generating electricity in a power station and transmitting it to the supermarket – so congratulations Sainsburys, your “green scheme” releases more CO2 than doing nothing would have done.