Electric vehicles are becoming increasingly popular in the UK, with more models available and improving infrastructure for charging. However, a common concern for prospective EV owners is how much charging an electric car will add to their electricity bill.
The cost of charging an electric car
The cost of charging an electric car depends primarily on two factors:
- The size of the EV battery
- The electricity rate you pay per kWh
Most electric cars have batteries between 40-100 kWh. Long range Tesla models like the Model S and Model X have 100 kWh battery packs, while more affordable EVs like the Nissan Leaf have batteries around 40 kWh.
The average electricity rate in the UK is currently around 15-20p per kWh for a standard variable tariff. Many EV owners switch to time-of-use tariffs which offer cheaper overnight rates of 5-10p/kWh for charging when demand on the grid is lower.
So for example, to charge a 40 kWh Nissan Leaf from empty to full might cost:
- 40 kWh x 15p/kWh = £6 on a standard variable tariff
- 40 kWh x 10p/kWh = £4 on an overnight time-of-use tariff
And to charge a 100 kWh Tesla Model S:
- 100 kWh x 15p/kWh = £15 on a standard variable tariff
- 100 kWh x 10p/kWh = £10 on an overnight time-of-use tariff
Annual charging costs
Based on average electric car usage, drivers charge their EV at home around 2-3 times per week. The average EV in the UK drives around 7500 miles per year.
So over a year an average EV might use:
- 40 kWh battery x 2.5 charges per week x 52 weeks = 5,200 kWh
- 100 kWh battery x 2.5 charges per week x 52 weeks = 13,000 kWh
Which would cost annually:
- 5,200 kWh x 15p/kWh = £780 per year for a 40 kWh EV
- 13,000 kWh x 15p/kWh = £1,950 per year for a 100 kWh EV
With an overnight time-of-use tariff the costs could be:
- 5,200 kWh x 10p/kWh = £520 per year for a 40 kWh EV
- 13,000 kWh x 10p/kWh = £1,300 per year for a 100 kWh EV
Cost comparisons with fuel
To compare running costs against petrol or diesel vehicles, a typical family car such as a VW Golf does around 40 mpg. At current UK fuel prices of around £1.20 per litre, that equates to:
- 7500 miles per year / 40 mpg = 187 gallons per year
- 187 gallons x £1.20 per litre = £225 per year on petrol
So a 40 kWh EV charged at the standard rate would cost around £780 in electricity versus £225 for an equivalent petrol Golf. However with cheap overnight charging the EV costs £520, only around double that of the petrol Golf.
And when comparing against less efficient petrol/diesel cars doing under 30 mpg, the annual fuel costs rise to over £300. So against these vehicles, an EV makes more financial sense.
Electricity bill impact
For the average household, charging an EV with a 40 kWh battery is equivalent to around 16-18% more electricity usage.
A household with typical usage of 3,100 kWh per year would use around 3,600 kWh with the addition of an EV charging 2-3 times per week.
So the household electricity bill may increase by £117-£156 per year assuming a standard electricity tariff. With cheap overnight charging, the increase would be around £78-£104 per year.
The impact is more pronounced for households that charge larger battery EVs, especially Teslas. A 100 kWh Tesla could add £650-£975 onto the annual household electricity bill.
Ways to mitigate increased electricity costs
There are a few ways EV owners can reduce the impact of charging costs on their electricity bills:
- Move to a cheaper time-of-use tariff and charge overnight or during daylight hours when rates are lower.
- Use public rapid chargers for some top-ups to avoid charging at home all the time.
- Take advantage of free charging incentives – some workplaces offer free EV charging benefits.
- Generate your own solar power during the day to offset EV charging usage.
- Only charge to 80-90% to reduce the kWh required unless you need full charge.
Cost per mile of driving an EV
Based on the projected annual costs above, we can determine the cost per mile to drive an electric car charged at home in the UK:
| EV Battery Size | Annual Charging Cost | Miles Driven | Cost Per Mile |
|---|---|---|---|
| 40 kWh | £520 | 7,500 | 6.9p |
| 40 kWh | £780 | 7,500 | 10.4p |
| 100 kWh | £1,300 | 7,500 | 17.3p |
| 100 kWh | £1,950 | 7,500 | 26p |
This compares very favourably to average petrol and diesel cars that cost around 12-16p per mile to run in the UK and up to 25p per mile for less efficient models.
Electricity usage comparisons
It’s also useful to understand how much electricity an EV will use compared to other household appliances.
Charging an electric car uses a similar amount of kWh as the following household items and annual costs:
- 40 kWh EV charged weekly = 5,200 kWh/year
- Equivalent to an old fridge/freezer running all year at 500 kWh x £150 = £780/year
- 100 kWh EV charged weekly = 13,000 kWh/year
- Equivalent to clothes dryer used 300 times per year at 4 kWh x £150 = £1,800/year
So while an EV adds significantly to electricity usage compared to not owning one, the charging requirements are comparable to the consumption of major appliances we already have in our homes.
Electric car charging speed impacts
Faster charging electric cars will typically use more electricity overall than slower charging EVs. That’s because faster charging enables drivers to charge up more quickly and drive farther more often.
For example, a Tesla Model 3 Long Range using the Supercharger network charges at over 150 kW compared to 7 kW home charging. This allows it to add hundreds of miles of charge in an hour.
While Supercharging is more expensive than home rates per kWh, the faster speed enables more miles driven per year. So the overall annual charging costs may be higher despite the slower overnight home charging being cheaper per kWh.
Outlook for future EV charging costs
In the next few years, electric car charging costs are expected to decrease in the UK due to:
- Falling electricity rates as more renewables come online
- Wider adoption of cheap time-of-use tariffs
- Smart charging technology to avoid peak rates
- Lower battery prices allowing more affordable EVs with shorter ranges
We should also see more workplace and public charging options available to reduce dependency on charging at home. Apps will allow EV drivers to easily locate and pay for charging across networks.
Overall electric car charging costs look set to decrease, making EVs more affordable to run for UK drivers regardless of charging location.
Conclusion
Charging an electric car rather than fuelling a petrol or diesel vehicle increases UK household electricity bills by an estimated £100-£200 per year on average.
For higher mileage drivers and larger battery EVs like Teslas, the annual charging costs can be £500-£1000 more than an equivalent petrol car.
But smart charging using time-of-use tariffs can greatly reduce the impact, with overnight rates as low as 5-10p per kWh available.
With the running cost per mile as low as 7-8p for electric cars charged overnight at home, EVs make financial sense for drivers covering average mileages. And as charging infrastructure improves, costs should come down further in the years ahead.