How much more electricity will the UK need to switch to electric vehicles?

Going to 100% electric cars would increase electricity demand by around one-quarter. Moving all road transport to electric would increase it by around 40%.

Electric car sales across the world are soaring. Countries are setting phase-out plans for petrol and diesel cars. And more manufacturers are shifting their focus to the EV market.

The future of road transport is electric.

That means we’re going to need more electricity. But how much? Will electricity demand double, triple, increase ten-fold?

Here I’ll run the numbers for the UK to see how much electricity we’d need if all of our cars, vans, lorries and buses went electric.

Since electric vehicles are much more efficient than petrol or diesel, we’ll also see how this move would decrease our total energy consumption.

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How much electricity would we need for fully electric cars?

Let’s start with cars. The UK Government plans to end the sale of new petrol and diesel cars by 2030. This doesn’t mean everyone will have to hand over their internal combustion engine in 2030: you just won’t be able to buy a new one. New plug-in hybrids will still be on sale until 2035.

In Great Britain, cars and taxis drive around 240 billion miles per year.¹ That’s 390 billion kilometres.

A standard electric car – here I’m using the Renault Zoe – uses around 171 Wh per kilometre.²

Multiply these two numbers together and we get the amount of electricity needed if all of these vehicles were Renault Zoes: 67 terawatt-hours (TWh).³

In 2021, Great Britain produced around 300 TWh of electricity.⁴ Demand – after trade, losses etc. – was 284 TWh.

That means that its cars going fully-electric would increase demand by around 24%.

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How much electricity would we need for fully electric road transport?

Let’s extend this to vans, lorries and buses. How much would we need if they also went electric?

For vans, we can run the numbers in the same way that we did for cars.

The Vauxhall Vivaro electric van has an efficiency of 263 Wh per kilometre. Vans in Great Britain travel 92 billion kilometres per year.⁵

Multiply these numbers and we get 24 TWh for fully electric vans.

I don’t have good figures on the efficiency of EV lorries and buses. But we can estimate these from their petrol equivalents.

Electric vehicles are 3.5 to 4 times as efficient as gasoline equivalents: as I covered in another post, only 20% of petrol actually gets converted into motion. This efficiency in EVs is around 80%. That would be 4 times as efficient. Diesel has a slightly higher efficiency than petrol – and lorries and buses tend to be diesel-powered – so let’s be conservative. We’ll say that EVs are 3.5 times as efficient.

From the UK’s road fuel statistics, I estimate that lorries use the equivalent of 83 TWh of diesel per year. If these were all electric, we might assume they’d use 3.5-times less energy. That’s 23 TWh.

Buses use 14 TWh of diesel. Going electric, they would use just 4 TWh.

That gives us:

• Cars: 67 TWh

• Vans: 24 TWh

• Lorries: 23 TWh

• Buses: 4 TWh

118 TWh in total for road transport.

That would increase electricity demand by around 40%.

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Electricity transport significantly reduces primary energy demand

If we were to electrify transport, we’d need much less energy overall.

When we look at the amount of energy that countries currently use, it can seem like an overwhelming challenge to replace all of this with low-carbon sources.

But, we don’t need to produce the equivalent amount of low-carbon energy. Our current energy stack includes the energy that we actually need, but it also includes all of the wasted energy in converting fossil fuels to something useful. When we switch to electric cars or low-carbon electricity, a lot of that disappears.

We can demonstrate that with transport.

Great Britain currently uses the equivalent of 445 TWh from petrol and diesel road vehicles.⁶ As we’ve just calculated, if this was electric we’d need just 118 TWh. Almost 4 times less. Our energy demand has shrunk dramatically.

Now, this only applies to electricity from solar and wind. If we were to produce this electricity from coal or gas, our energy inputs would be much higher. That’s because a lot of energy would be wasted as heat in the power plant.

In a coal plant, only around 32% of energy is converted to electricity.⁷ So to get our 118 TWh out, we’d need to put 368 TWh of coal in.

A gas plant is around 45% efficient. To get 118 TWh out, we’d need to put 262 TWh in.

Now, most countries do not run on 100% coal or gas, so this is an extreme case. But as we can see in the chart, even with an electricity grid rich in coal or gas, electric vehicles are still more efficient than petrol and diesel.

For maximum efficiency, electric vehicles should be powered by low-carbon electricity.

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Conclusion

Electrifying our cars will increase electricity demand by around one-quarter. Electrifying all of our road transport will increase demand by 40%.

This seems do-able to me. What will be more challenging is managing peak times, when everyone wants to charge their car. Here, incentives such as dynamic pricing would be crucial. For example, offering cheaper rates near the middle of the day when solar is at its peak (and other demand loads are not at their peak).

And a big win for electric transport is that it will reduce our overall energy demand. A big chunk of our energy stack will disappear – most of it is wasted as heat in our engines anyway.

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1. Note that Great Britain is the UK minus Northern Ireland. My only reason for using Great Britain figures is that these are the statistics reported by the Government in its National Statistics: https://roadtraffic.dft.gov.uk/summary

2. There are, of course, more efficient models.

The Tesla Model 3 uses just 144 Wh per kilometre.

3. We get this in the following way:

171 * 390 billion = 67 trillion watt-hours.

1 TWh = 1 trillion watt-hours.

So, that's 67 TWh.

4. Again, I haven’t included Northern Ireland here, so the numbers are comparable to earlier figures.

https://www.gov.uk/government/statistics/energy-trends-december-2022-special-feature-article-electricity-generation-and-supply-in-scotland-wales-northern-ireland-and-england-2017-to-20

5. The UK Government reports 57.5 billion miles.

That's equal to 92 billion kilometres [57.5 * 1.6].

https://roadtraffic.dft.gov.uk/summary

6. To get these numbers, I took fuel use from the UK Government's statistics: https://www.gov.uk/government/statistical-data-sets/energy-and-environment-data-tables-env#fuel-consumption-env01

These are reported in tonnes.

I converted these figures to litres.

Then I converted to MJ using a conversion factor of 32 MJ per litre for petrol, and 36 MJ per litre for diesel.

Convert from MJ to TWh using a conversion factor of 0.278, multiplied by one billion.

Finally, I adjusted from UK demand to Great Britain demand using UK population statistics by country. I assumed that Northern Ireland had a similar per capita demand to other nations.

https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationestimates/bulletins/annualmidyearpopulationestimates/mid2021

7. For coal and gas plant efficiencies, I've taken the conversion factors used by the US Energy Information Administration (EIA).

https://www.eia.gov/todayinenergy/detail.php?id=44436