Free EV savings calculator
EV savings calculator: how much could you save by switching to electric?
Compare what you spend on petrol or diesel today with the cost of charging an electric car at home — and see how much charging you’d actually need. Takes about a minute.
How the EV savings calculator works
The calculator compares what you spend on petrol or diesel today with what the same miles would cost in electricity. It uses three simple sums:
- Fuel cost = (miles a year ÷ mpg) × 4.546 litres per gallon × price per litre.
- Electricity used = miles a year ÷ the EV’s miles per kWh.
- EV cost = electricity used × your blended price per kWh (your home rate and any public charging, weighted by how much of each you use).
It also works out how much charging you would need each day and week, and how long that takes on a 7kW home charger — usually far less than people expect.
Electric vs petrol: a worked example
Take a driver covering 10,000 miles a year in a 40mpg petrol car, with petrol at £1.45 a litre. That is about 1,137 litres a year, or £1,648. The same 10,000 miles in an EV averaging 3.5 miles per kWh needs about 2,857kWh of electricity. What that costs depends almost entirely on where you charge:
| How the EV is charged | EV cost a year | Cost per mile | Saving vs petrol |
|---|---|---|---|
| At home, off-peak EV tariff (7p/kWh) | £200 | 2.0p | £1,448 |
| At home, mid-rate (15p/kWh) | £429 | 4.3p | £1,219 |
| At home, standard tariff (26p/kWh) | £743 | 7.4p | £905 |
| 70% home off-peak, 30% public (55p/kWh) | £611 | 6.1p | £1,036 |
| All public rapid charging (55p/kWh) | £1,571 | 15.7p | £76 |
The pattern is clear: charging at home on an off-peak tariff is what makes an EV cheap to run. Rely only on public rapid chargers and the saving all but disappears. See how much it costs to charge an electric car at home and Octopus Intelligent Go vs Go.
How much you could save by mileage
The more you drive, the bigger the saving. Here is the same comparison across typical annual mileages.
| Miles a year | Petrol cost | EV, off-peak (7p) | Saving | EV, standard (26p) | Saving |
|---|---|---|---|---|---|
| 5,000 | £824 | £100 | £724 | £371 | £453 |
| 7,500 | £1,236 | £150 | £1,086 | £557 | £679 |
| 10,000 | £1,648 | £200 | £1,448 | £743 | £905 |
| 12,000 | £1,978 | £240 | £1,738 | £891 | £1,086 |
| 15,000 | £2,472 | £300 | £2,172 | £1,114 | £1,358 |
| 20,000 | £3,296 | £400 | £2,896 | £1,486 | £1,810 |
What the calculator does not include
This is a running-cost comparison: fuel against electricity. It leaves out the purchase price or lease cost, insurance, servicing, tyres, vehicle tax and depreciation. EVs generally need less routine servicing because there is no oil, clutch or exhaust, but they have paid vehicle excise duty since April 2025 and can cost more to insure. Weigh those up alongside your fuel saving. Our electric car vs petrol running costs guide covers the wider picture, and company car drivers should read home chargers for company and lease cars.
Does a home charger pay for itself?
A standard home charger installation typically costs £800–£1,200. In the 10,000-mile example above, the gap between charging at home off-peak (£200 a year) and relying on public rapid chargers (£1,571 a year) is over £1,300 a year. If the alternative is relying on public chargers, a home charger can pay for itself within a year or so; even against a slow three-pin plug, it makes off-peak charging fast and automatic. See our EV charger installation cost page for typical prices, or get a free quote and we’ll help match you with a suitable local installer.
EV savings FAQs
How much can I save by switching to an electric car?
At 10,000 miles a year, swapping a 40mpg petrol car (petrol at £1.45 a litre) for an EV charged at home on a 7p/kWh off-peak tariff cuts fuel costs from about £1,648 to about £200 — a saving of roughly £1,450 a year. On a standard 26p/kWh tariff the saving is still about £905 a year.
Is it cheaper to run an electric car than a petrol car?
Usually, if you can charge at home. Home charging on an off-peak EV tariff works out at around 2p per mile, against around 16p per mile for a 40mpg petrol car. If you rely entirely on public rapid chargers, the running cost can be close to petrol.
How much does it cost to charge an electric car per mile?
Divide your electricity price by your car’s efficiency. At 3.5 miles per kWh, 7p/kWh is 2p per mile, 26p/kWh is about 7.4p per mile, and 55p/kWh at a public charger is about 15.7p per mile.
What does the EV savings calculator not include?
It compares fuel against electricity only. It does not include the purchase price, finance, insurance, servicing, tyres, vehicle tax or depreciation, which can all differ between petrol and electric cars.
Do I need a home charger to get these savings?
Home charging is where almost all of the saving comes from, because it gives you access to cheap overnight tariffs. A home charger makes overnight charging fast, safe and automatic.
What miles per kWh should I use for an EV?
Around 3.5 miles per kWh is a fair average for mixed UK driving. Small, efficient cars can manage 4 or more; large SUVs, winter driving and motorway speeds can bring it down to 2.5–3.