What difference will electric cars make to our electricity demand

Simple calculation[s] as to the impact on electricity demand as we progressively switch over to electric cars.

National Grid estimates up to 7% increase in electricity demand by 2040 for EVs

There are around 30 million cars on the road today [1]. National Grid’s Future Energy Scenarios 2016 presents 4 scenarios – in the most ambitious ‘Gone Green’ scenario there are 9.7 million electric vehicles (EV) on the roads in 2040 using an extra 24 TWh/year. Relative to current electricity demand that is an increase of 7%[2].

But the impact on peak demand will be minor, if drivers respond to time of use pricing.

However, this demand is highly unlikely to be spread evenly through the day and year. Firstly, people tend to drive more in the summer, presumably because it is considerably more pleasant than driving in the winter [3]. Fortunately our peak electricity demand is in the winter so this helps to even out the load.

Secondly, assuming time of use pricing is widely adopted drivers will try quite hard to charge their vehicles at times of the day when the electricity is cheap. Most people will have quite a lot of flexibility and during the peak time a lot of drivers are on the road anyway.

This means electric car charging will increase non-peak demand much more than peak. The chart below shows a typical January day. If electric car charging is spread over non-peak times it will start to fill in the yellow area but not impact on the peak demand. 24 TWh/year is 66 GWh/day so it could fill in just over a quarter of the yellow area.

A typical day’s UK electricity demand in January

If all cars were electric there would be more impact on peak demand

However, 66 TWh/day is from only 9.7 million electric vehicles. If we replaced all 30 million cars, it would be nearer 200 GWh/day. This does still fit into the yellow area – just – but it would be quite a challenge to ensure that there was no ‘leakage’ and it did not impact on the winter peak at all.

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