Re: Fag packet calculation time...
"Work out how much energy the UK car fleet consumes per year, when it burns petrol/diesel. For 2016 it was around 140TWh petrol, 130TWh diesel (with another 150TWh for haulage), calculated as Tonnes of Oil Equivalent (TOE). UK annual electricity consumption is 360TWh, so to recharge all those vehicles from the grid would require more than doubling electricity production."
Completely nonsensical. You are talking about one form or fuel, engine, technology and doing a direct conversion to another?
As well as different efficiencies you also have to look at the electricity required for refining petrol/diesel as well as the energy require in the logistics of delivery, extraction etc.
It is pointless starting with ICE and converting when electric cars already exist and their capacity, charge capabilities and efficiencies are already known. Anyone who starts with that calculation is not going to come out with a reasonable answer.