There are many methods for producing synthetic fuels, I think those using sea water look most interesting, so we'll use those as an example. https://en.wikipedia.org/wiki/Carbon-neutral_fuel "The U.S. Navy estimates that 100 megawatts of electricity can produce 41,000 gallons of jet fuel per day and shipboard production from nuclear power would cost about $6 per gallon." https://en.wikipedia.org/wiki/Heather_Willauer "In 2012, Willauer estimated that jet fuel could be synthesized from seawater in quantities up to 100,000 US gal (380,000 L) per day, at a cost of three to six U.S. dollars per gallon."
So, that basically means that the wholesale electricity cost of 41,000 US gallons (155201L) is 2400mw/h x £40(today's wholesale per mw/h) = 61p per Litre.
Internal combustion engine(ICE) cars are now edging towards achieving 100 mpg. There are new engine technologies hoping to improve this, such as http://achatespower.com/our-formula/opposed-piston/
Hybridisation using batteries, flywheels or compressed gas can improve efficiency still further by regeneration energy lost under braking.
Point is, if we can get the cost of a 100 mile journey using ICEs to £2.77 (61x4.55) that is also carbon neutral, is it worth pursuing an expensive transition to battery only powered cars? Where a 100 mile journey, which is not CO2 neutral, costs around 30kw/h at 12p per kw(retail), adding up to £3.60
Of course I am not comparing like for like ie wholesale vs retail. But then a large manufacturer of synthetic fuels would probably have their own plant or negotiate low prices. Maybe it would be worth building a dedicated nuclear power plant for the job?
The UK currently uses 45 billion litres of petrol/diesel every year. If continuing efficiency can half this we'd need around 45gw of extra electric generation to make the equivalent in synfuel.
That's roughly the equivalent of 12 Hinkley Point C, to end our dependency on petrol and diesel imports, and reducing net CO2 emissions by 120 million tonnes per year. Hybrid cars may be a good idea. What may not be a good idea is to replace the internal combustion engine and all the infrastructure created for it, with a technology that is more expensive, less convenient, and will require an massive and expensive upgrade in infrastructure.
