The best I can find from retail fuel figures is more like 14 - 16 kWh / p / d of fuel. (realclimate.org)
For the convenience industry alone, this will require a minimum infrastructure investment that will add nearly $ 22 billion to the cost of retailing fuels.» (americanenergyalliance.org)
Anne, I can not reconcile your 20km / p / d with actual retail fuel in UK. (realclimate.org)