Q - would we have enough electricity generating capacity if each household in the UK had one electric car?
A - I don't know, but here's how I would guesstimate it. Feel free to pile in if you have better info.
---------------------------------------------
Typical daily electricity usage per household - 9.25 kWh (from here)
Add on 50% for the electricity people use when out of the home, i.e. at work or at school = 13.875 kWh (a rough guess, I can't find a more accurate figure).
That's (say) 16 hours a day, grid running at near full capacity.
That leaves 8 hours where not much electricity is being used (another assumption), in which time power stations, if they continued running at near capacity, could generate another 6,9375 kWh per household per day (5,775 x 8/16), call it 7 kWh in round numbers.
Electric cars can do 2.9 miles/kWh (from here).
7 kWh x 2.9 miles/kWh = about 20 miles (per car per day).
About half of all car miles are commuting, and the average journey (one way) is less than 10 miles, so most of us would be OK for commuting and a weekly shopping trip. Some would do a lot less than that, some would do more, it might well average out.
Clearly, overall use would have to come down a lot. 28 million households/cars x 20 miles/day x 365 days/year = about 200 billion miles a year.
Total miles driven in the UK per year (car, van, taxi) = 658 billion km = 409 billion miles.(from here).
So ball park, yes, if we ran power stations 24 hours a day, and reduced overall miles driven by half (more public transport, more car sharing, work nearer home or from home, don't go on holiday by car, no driving round just for the joy of it* - a problem which solves itself), we could just about manage.
It's still a ridiculous idea, for many other reasons**, but on this narrow point, I think the idea just about passes the feasibility test.
---------------------------------------------
* Most of the miles I drive, to be honest.
** Negative impact of CO2 on climate has been exaggerated ten- or a hundred-fold; it will he hugely expensive, there isn't enough copper for the cables or rare metals for the batteries; it will take decades to switch over and electric cars are no fun, but hey.
Debate Magazine
