What a charge actually costs — including the energy lost on the way into the battery.
Enter your car, the charge you want and the price you pay, and this works out what the session costs, how long it takes, and what that comes to per mile. Unlike most charging calculators it also shows charging losses — the electricity your meter records but the battery never receives.
Car and charge
Electricity price
Preset prices are indicative UK defaults set in August 2026 — electricity prices move, so check yours and type over the value. Anything you type is saved against the selected preset, so you can switch between them without losing your figures. Pick Custom to keep your own price, charger speed and efficiency untouched by the presets.
Charging setup
£3.00
Cost for this charge
Energy into the battery36.00 kWh
Energy drawn from the grid40.00 kWh
Charging loss4.00 kWh
Cost per percentage point£0.05
Charging time4h 52m
Range added126 miles
Cost per mile2.38p
Time is a flat estimate. On a rapid charger the car slows itself sharply above roughly 80% to protect the battery, so a 20–80% session is far quicker than the last 20% alone.
Full charge (0–100%) cost£5.00
Full charge range210 miles
Compared with petrol or diesel
£1,226.76
Saved per year against petrol
Petrol cost per mile14.65p
EV cost per mile2.38p
Saving per mile12.27p
Fuel and energy only — it excludes tax, insurance, servicing and depreciation, which differ between the two.
How it works
Four formulas do all the work:
Energy into the battery = battery kWh × (target% − current%) ÷ 100 Energy drawn from the grid = energy into the battery ÷ (efficiency ÷ 100) Cost = energy drawn × price per kWh + session fee Charging time = energy into the battery ÷ charger kW
The second line is the one most calculators skip. You are billed for what passes through your meter, not what reaches the battery, so the grid figure is always the larger of the two and it is the one that determines the cost.
For the petrol comparison, an imperial gallon is 4.54609 litres, so petrol cost per mile = (price in p/litre × 4.54609) ÷ mpg. At 145p a litre a gallon costs £6.59, and at 45 mpg that is 14.65p per mile.
Worked example
A 60 kWh car charged from 20% to 80% at home on an off-peak EV rate of 7.5p per kWh, at 90% efficiency on a 7.4 kW home charger.
The battery receives 60 × (80 − 20) ÷ 100 = 36 kWh. At 90% efficiency the meter records 36 ÷ 0.9 = 40 kWh, so 4 kWh is lost as heat in the charger, cabling and battery. The cost is 40 × 7.5p = £3.00, which is 5p per percentage point. It takes 36 ÷ 7.4 = 4 hours 52 minutes. At 3.5 miles per kWh those 36 kWh are worth 126 miles, so the drive costs 2.38p a mile.
The same charge on a public rapid at 79p per kWh costs £29.94 — ten times as much, for exactly the same miles.
Why you rarely charge 0–100%
Almost nobody runs an EV from empty to full. Most manufacturers suggest keeping a lithium-ion battery roughly between 20% and 80% for daily use, because sitting at a very high or very low state of charge accelerates degradation. Rapid chargers also slow dramatically above about 80%, so the last fifth of a charge can take as long as the first three-fifths. That is why the calculator defaults to a 20–80% session rather than a full charge, though the full-charge figure is shown separately for reference.
What causes charging losses
Energy is lost converting AC from the grid into DC for the battery, as resistance in the cable, and as heat in the battery itself. Thermal management adds more: in cold weather the car may heat the pack before and during charging, which draws power that never gets stored. Slow AC charging typically runs around 85–92% efficient, while DC rapid charging bypasses the car's onboard converter and is usually a little better, around 94–96%. Charging in the cold at low power is the worst case, because a fixed overhead is spread over fewer kWh.
Why the tariff matters more than the car
The spread between the cheapest and dearest way to buy the same kWh is enormous. A dedicated off-peak EV tariff overnight can be under 10p per kWh; a public rapid can be eight to ten times that. Nothing else in the calculation moves the answer as much — not the car, not its efficiency, not the weather. If you can charge at home overnight, that single fact does more for your running costs than any other choice you make.
Electricity prices change often. The preset prices here are indicative defaults set in August 2026 and are not a live feed, so check your own tariff and your charging network's current rates and type them in. The Custom preset exists for exactly that: it never overwrites your price, charger speed or efficiency.
A note on currency and units
The currency selector changes the symbol shown against your results only — it does not convert between currencies, so enter every figure in the currency you have picked. Prices for electricity and fuel are entered in the minor unit, which is pence per kWh and pence per litre in the UK, and the equivalent hundredth of the main unit elsewhere.
Fuel economy stays in miles per gallon using the imperial gallon of 4.54609 litres, which is the UK convention. If you are working in US mpg, note that a US gallon is 3.785 litres, so a US mpg figure needs converting before it will give the right answer here.
Frequently asked questions
How much does it cost to fully charge an electric car in the UK?
It depends almost entirely on where you charge. A 60 kWh car needs about 67 kWh from the grid for a full charge at 90% efficiency. On a 7.5p off-peak home tariff that is about £5; on a public rapid at 79p per kWh it is closer to £53. Same car, same electricity, ten times the price.
Why is the electricity drawn more than the battery receives?
Because charging is not perfectly efficient. Energy is lost as heat in the onboard charger, the cable and the battery, plus whatever the car spends warming or cooling the pack. Your meter bills the larger figure, so a 90% efficient charge of 36 kWh actually costs you 40 kWh.
Is charging at home really that much cheaper than public charging?
Yes, and the gap is the single biggest factor in EV running costs. An off-peak home tariff is typically well under a third of a public fast charger and around a tenth of a rapid. If you have off-street parking and a home charger, using it overnight is worth more than any efficiency gain from the car itself.
Why does rapid charging slow down after 80%?
To protect the battery. As cells fill, the car reduces the current it will accept to limit heat and degradation — this is called tapering. The practical effect is that going from 20% to 80% is often quicker than 80% to 100%, which is why rapid stops are usually planned around the 20–80% window.
What efficiency figure should I use?
Around 90% for AC home or workplace charging and about 95% for DC rapid, which is what the presets set. Drop it a few points in cold weather or when charging at very low power, since the fixed overhead is then spread across fewer kWh.
Are the preset prices kept up to date?
No — they are indicative defaults set in August 2026, not a live feed. Energy prices and public charging rates change regularly, so treat them as a starting point, check your own tariff, and type the real number in. Anything you type is stored against whichever preset is selected, and the Custom preset leaves your own figures alone entirely.
Can I use this outside the UK?
Yes. Pick your currency and enter the price in that currency's minor unit per kWh. The selector only changes the symbol — it does not convert between currencies, so keep every figure in the one you have chosen. One caveat: fuel economy is miles per imperial gallon (4.54609 litres), so a US mpg figure needs converting first.