The Impact Of EVs On Grid Capacity

By Paul Homewood


As promised, some more reflections on the grid implications for EVs:

A woman, circa 1912, hand-cranks the charger for her electric Columbia Mark 68 Victoria. 

First, let us recap the Committee on Climate Change’s calculations for  fully electric fleet:


Unfortunately I have lost the link, but only the other day the National Grid was still insisting that they would only need 10% extra capacity to cope – that is about 5 GW.

So, to my fag packet!

Based on the Nissan Leaf, you can expect about 100 miles from a 40 KWh battery. [Their official figure is 168 miles, but this assumes perfect driving conditions. The Leaf is also a tiny car, so my 100 miles assumption is not unreasonable for an average car size]

Based on an annual mileage of 10,000, a car would therefore consume 4000 KWh a year. There are 33 million cars on the road in the UK, so this would add up to 132 TWh a year, much higher than the CCC’s estimate. (Note as well that they assume 46 million cars.) I may of course be overestimating average miles. However, there is a double check.

According to the OBR, fuel duty brings in £28.4bn a year at 57.95p/litre. Assuming an average of 40 mpg, this works out at about 13,000 miles a year on average for every car.

However, assuming the CCC is correct, if all cars were charged up between midnight and 6 am, the average load from EVs during those hours would be 35 GW.

As the chart below shows, the current load at night during January is about 30 GW, indicating the need for at least 65 GW. This is 20 GW higher than the peak daytime load, making a nonsense of the Grid’s claims.


Of course, some cars may charge during the day, but this will simply add to demand which the grid is already struggling to meet, particularly when every house relies on a heat pump.

If my guesstimate of 132 TWh is correct, we would need an extra 60 GW of capacity, instead of 35 GW.

Let’s carry on with the CCC assumption, and suppose that EVs are charged up evenly for a 12 hour period, between 6pm and 6am. This would need capacity of 18 GW, but at 6pm demand is at a peak of 45 GW, so we would still need at least 63 GW, so this scenario is little better.

But what is the likelihood that cars will be charged up at these times that are convenient to the grid? In my view, extremely unlikely.

The official view is that we will all be using smart chargers, which only switch on when there is spare power around. But smart chargers currently do no such thing – they are merely pre-set timers, to allow you to set the time you want them to come on.

Moreover smart chargers cost typically £1000 or more. Many drivers will refuse to pay this, and simply plug into a household socket.

A further problem is that most drivers park on the drive at night. If the charger is in the garage, that means leaving the garage door open. Nobody in their right mind would leave the door open at night, an open invitation to steal bikes, lawn mowers and tools! Even if the charger is outside the garage, you are still likely to get the cable nicked if it is left out all night.

I suspect that most drivers will simply plug in as soon as they get home from work out of convenience, and do this everyday, and not just when the battery is low. Even if the price of electricity is lower at night, the savings would only amount to a few pence, so who is going to bother?

Under this scenario, the demands on the grid will be much greater.Even generously assuming that cars are plugged in in an evenly staggered fashion between 6pm and 10pm, you would need 51 GW of capacity. And this at a time when demand is at a peak of 45 GW.

In reality, although the average car might only need an hour or two charge each night, most drivers will start charging up in a small band of time, with most cars being charged between 6pm and 8pm. Under this scenario, and assuming half of the nation’s cars on charge at this time, we would need capacity of 112 GW. [16 million cars at 7 KW]

All of this, of course, applies to the time when all cars are electric. But with the new ban, it is likely that half of Britain’s cars will be electric by the mid 2030s, given annual sales of 2.5 million. It is inevitable that many EVs will be sold in the years leading up to 2030, as manufacturers begin to phase them in.

We could therefore very quickly see a lot of extra capacity being needed by then. We cannot rely on wind power, and if nuclear energy is to be relied on, it will have to start being built now.


November 20, 2020 at 09:09AM

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