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When will the lights go out?

By Mark Hanlon - Last updated: Friday, September 29, 2017

A nice cup of teaI’m sure you’ve seen the headline, that if we were all to switch to electric vehicles (EVs) tomorrow the grid wouldn’t cope and, with a dramatic flourish, the lights would go out. Is this what will happen on January 1st, 2040, when the sale of diesel and petrol fuelled cars is banned? The Telegraph suggested that this planned ban was unravelling due to the ten new power stations that would have to be built to cope with the increased electricity demand. And at the micro-scale, the National Grid in a ‘thought piece’ stated that your home fuse could blow if you tried to boil a kettle while charging your electric car. This EV revolution is clearly a non-starter.

As an EV owner for approaching 18 months now, I’ve read these stories with interest. Particularly as I also enjoy a good cup of tea. It turns out that the writer of the National Grid piece made an assumption that home chargers would run at 11kW, drawing 48amps, which with another 10amps from a kettle would bring you precariously close to tripping a 60amp mains fuse. In truth, typical home chargers in the UK max out at 32amps (7kW) and to go beyond this requires a three-phase installation with three fuses, allowing much more power to be drawn.

How long to charge?

They have a point though don’t they? To ‘fill my tank’ at home I’ll need a really high-powered charger, otherwise it’ll take days. It’s true that fully charging a 90kWh battery through a three-pin plug at 10amps will take around 40 hours. But this doesn’t consider the change in behaviour that EVs encourage. Conventional petrol tanks tend to be driven until almost empty and are then filled to the brim by making a trip to the nearest petrol forecourt. EV charging is more akin to mobile phone charging – you top up whenever is convenient, ideally nightly. With the average round-trip commute in the UK being less than 20 miles, even the slowest form of charging via a 10amp plug will complete during the Economy 7 cheap rate period, putting minimal strain on the home electrics. My midnight cuppa is safe!

It’s the attraction of charging whilst sleeping that was ignored in the Telegraph article. The national grid has been designed to cope with the peak of demand, meaning that overnight there’s a large amount of available capacity. I randomly picked a Wednesday in April of this year and downloaded the UK electricity consumption figures from the 8pm peak through to 8am the next morning, and then roughly calculated how much available energy the trough represented. The total of 94GWh is enough to charge just under 19 million extra electric cars ready for their Thursday commute, without the need for any new power stations.

EV energy 1920

Drive by the sun

This back-of-an-envelope calculation also doesn’t take into account the saving in electricity currently used in the oil refinement process, or the opportunity to (at least partly) charge an EV with energy gathered by solar panels installed at home. It’s even possible to build your own charger that diverts any spare solar energy into your car with the open source OpenEVSE framework.

Tony Seba explained in his Clean Disruption video that we are heading for a perfect storm of electric vehicles, autonomous driving and cheap solar. That’s why I found all the negative press about the 2040 ban rather perplexing. In my opinion, by then it simply won’t make economic sense to buy a petrol or diesel car. Indeed, I think this will be the case a decade earlier, and Scotland’s recent announcement of a 2032 fossil-fuel ‘phase out’ supports this.

Park and charge

Our new multi-storey car park was opened at the end of August here at Cambridge Consultants head office, and included six 22kW EV chargers. This will help make EV ownership viable for people without off-street parking at home, allow hybrids to travel further on pure electric, and provide a useful top-up for our visitors.

Electric cars are an inevitable part of our future; a future that also includes working light bulbs and hot tea.


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AuthorMark Hanlon


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