'Typical gasoline-powered auto engines are approximately 27% efficient. Typical fossil-fueled generating stations are 50% efficient, transmission to end user is 67% efficient, battery charging is 90% efficient and the auto's electric motor is 90% efficient, so that the fuel efficiency of an electric car is also 27%. However, the electric car requires 30% more power per mile traveled to move the mass of its batteries.CO2 emissions from domestic transport account for 24% of UK CO2 emissions, and cars, vans, and taxis represent 90% of road transport (DfT, 2013). Assuming 80% of fuel use is by these autos, they account for 19.2% of UK CO2 emissions. Conversion to electric power, 61% of which is generated by fossil fuels in the UK, would abate 39% of 19.2% (i.e. 7.5%) of UK CO2 emissions
However, the battery-weight penalty would be 30% of 19.2% of 61%: i.e. 3.5% of UK CO2 emissions. The net saving from converting all UK cars, vans, and taxis to electricity, therefore, would be 4% of UK CO2 emissions, which are 1.72% of global CO2 emissions, abating 0.07% of global CO2 emissions of 2 ppmv yr–1, or 0.00138 ppmv. Assuming 400 μatm concentration at year end on business as usual, forcing abated by the subsidy for converting all UK cars to electricity would be 5.35 ln[400/(400-0.00138)], or 0.00002 W m–2, which, multiplied by the Planck parameter λ0 = 0.31 K W–1 m2, gives 0.000006 K warming abated by the subsidy.The cost to the UK taxpayer of subsidizing the 30,000 electric cars, vans, and taxis bought in 2012 was a flat-rate subsidy of $8333 (£5000) for each vehicle and a further subsidy of about $350 (£210) per year in vehicle excise tax remitted, a total of $260.5 million. On that basis, the cost of subsidizing all 2,250,000 new autos sold each year (SMMT, 2013), would be $19.54 bn.Though the longevity of electric autos is 50% greater than that of internal-combustion autos, the advantage is more than canceled by the very large cost of total battery replacement every few years. No allowance for this extra cost is made. Likewise, the considerable cost of using renewable energy to bring down the UK's fossil-fueled generation fraction from the global mean 67% to 61% is not taken into account, though, strictly speaking, an appropriate share of the cost of "renewable" electricity generation should be assigned to electric vehicles.Dividing the $19 bn annual cost by the warming abated gives a unit abatement cost of $3400 tn K–1. Abating the 0.013 K projected warming over the study period by global methods of equivalent unit cost would thus cost $45 tn, or approaching $6500 a year per head of global population, or almost two-thirds of $71 tn global annual GDP.'