EV Charging Cost Calculator: What It Costs to Charge Your Electric Car

Work out your charging cost above

Enter your battery capacity and your electricity rate in the tool at the top of the page, and it returns the cost of a charge in seconds. The sections below explain the maths behind that number, walk through real examples, and show where home and public charging part company on price.

How the EV charging cost calculator works

Charging an electric car is just buying electricity, measured in kilowatt-hours (kWh). Your battery has a capacity in kWh, your energy supplier charges you a price per kWh, and the cost of a charge is simply one multiplied by the other. The formula is as plain as it gets:

Cost of a full charge = battery size (kWh) × electricity price (per kWh)

If you are only topping up rather than charging from empty to full, you scale it by how much of the battery you are filling:

Cost of a partial charge = battery size × (percentage added ÷ 100) × price per kWh

There is one real-world adjustment worth knowing about. No charger is perfectly efficient: some energy is lost as heat in the cable, the car's onboard charger and the battery itself. Home AC charging typically loses somewhere around 10% to 15%, so the electricity that leaves your meter is a little more than the energy that lands in the battery. A more honest version of the formula divides by an efficiency factor:

True cost = (battery size × price per kWh) ÷ charging efficiency

So for a 90% efficient charge you divide by 0.90, which pushes the cost up by roughly a tenth. Public rapid DC chargers tend to be more efficient at the car end but cost far more per kWh, which is where the real price gap appears. The calculator lets you set the price per kWh directly, so you can model home rates, public rates, or an off-peak overnight tariff without doing any of this by hand.

Battery size and your kWh rate: the two numbers that matter

Everything hinges on two inputs, so it pays to get them right.

Battery size (kWh). This is your car's usable battery capacity, not its range. A small city EV might have a 40 kWh battery; a typical family electric car sits around 58 to 64 kWh; larger models run to 77 kWh or more. The figure is in your car's spec sheet, usually quoted as a gross and a slightly smaller usable capacity. Use the usable figure if you have it.

Price per kWh. At home this is the unit rate on your electricity bill, set against the energy price cap that Ofgem updates each quarter. If you are on a standard variable tariff you pay one rate around the clock. If you are on a time-of-use or dedicated EV tariff, you may pay a much lower rate during a set overnight window and a higher rate the rest of the day. Public charging is priced separately by each network and is almost always dearer, sometimes two to three times your home rate, because it bundles in the cost of the hardware, the site and rapid delivery.

Home vs public charging: where the cost really splits

The single biggest driver of what you pay is not your car, it is where you plug in. Home charging on an overnight EV tariff is usually the cheapest electricity a UK household can buy. A standard home rate is more expensive than that but still well below public prices. Public rapid and ultra-rapid chargers sit at the top because you are paying for speed and convenience.

Roughly speaking, most drivers do the bulk of their charging at home and use public chargers only for longer journeys. That mix matters: if 80% of your miles come from cheap home charging and 20% from pricier public sessions, your average cost per mile is much closer to the home figure than the public one. The calculator lets you price each scenario on its own so you can see the spread, then weight it however your week actually looks.

Worked example: charging a family EV at home

Take Priya, who has just bought a used electric car with a 60 kWh battery and charges it overnight on her driveway. Her electricity unit rate is 25p per kWh on a standard tariff. To charge from empty to full:

• Energy needed: 60 kWh
• Cost = 60 × £0.25 = £15.00 for a full charge, before efficiency losses
• Allowing for 90% charging efficiency: £15.00 ÷ 0.90 = £16.67

If that 60 kWh gives her around 200 miles of real-world range, her home cost works out at roughly 8.3p per mile on the raw figure, or about 9.3p per mile once you account for the efficiency loss. Now compare the same full charge at a public rapid charger priced at 79p per kWh:

• Cost = 60 × £0.79 = £47.40 for the same full charge

Same car, same battery, more than three times the price. Over a year that gap is the difference between charging being one of the cheapest parts of running a car and one of the more annoying ones.

Worked example: an overnight top-up

Now imagine Priya only needs to add 40% to her battery overnight, and she has switched to an EV tariff with a 7p per kWh off-peak rate:

• Energy added = 60 kWh × 0.40 = 24 kWh
• Cost = 24 × £0.07 = £1.68

That same 40% top-up at the 79p public rate would cost 24 × £0.79 = £18.96. The off-peak top-up is under a tenth of the public price. This is why so much EV advice comes down to a single point: charge at home, overnight, on the right tariff, and the running cost looks very different from the headline figures you see at motorway services.

EV cost per mile vs petrol

To compare an electric car with a petrol one, convert both to pence per mile. For the EV:

EV pence per mile = cost of a full charge ÷ miles you get from that charge

Using Priya's home charge: £15.00 ÷ 200 miles = 7.5p per mile (or about 8.3p with efficiency losses). For a petrol car you divide the pump price per litre by the car's miles per gallon, after converting gallons to litres. A petrol car doing 45 mpg with fuel at £1.45 a litre costs roughly 14.6p per mile. So home-charged electric driving can be around half the per-mile fuel cost of an equivalent petrol car, sometimes far less on an off-peak tariff. Public-only charging narrows or even closes that gap, which is the part many switchers do not expect. If you want to run the petrol side of that comparison properly, our fuel cost calculator and cost per mile calculator handle the mpg-to-pence-per-mile maths for you.

Cutting your EV charging costs

A few practical moves make a real difference to what you pay:

• Get on an EV or time-of-use tariff. A dedicated overnight rate is usually the single biggest saving available, often cutting the unit price by two-thirds or more compared with a standard rate.
• Set a charge schedule. Most EVs and home chargers let you set charging to start automatically inside the cheap window, so you never pay peak rates by accident.
• Avoid charging to 100% routinely. For daily driving, topping up to 80% is gentler on the battery and usually all you need, which also keeps each session cheaper.
• Plan public charging. Networks vary a lot on price. A little planning to use cheaper destination or slow chargers on longer trips, rather than defaulting to the most expensive ultra-rapid unit, adds up over a year.
• Watch your home energy mix. EV charging sits on the same meter as the rest of your house, so the overnight rate you negotiate affects everything. Our energy bill calculator helps you see the charging cost in the context of your whole bill.

If you run an electric car through a company scheme or claim mileage, the tax treatment is a separate question from the electricity cost, and it is worth checking the rules. Our car tax calculator covers the vehicle duty side for different cars.

Common mistakes to watch out for

The EV charging cost calculator only gives you an accurate figure if your inputs are right, and a few errors come up again and again:

• Confusing battery size with range. A 60 kWh battery and a 60-mile range are completely different things. The calculator wants the kWh capacity, not how far the car goes.
• Forgetting charging losses. The energy that enters the battery is not the same as the energy that leaves your meter. Ignoring the roughly 10% to 15% home AC loss understates the real cost slightly, so allow for it on home charging.
• Using the wrong unit rate. A standard daytime rate, an off-peak EV rate and a public network rate can differ by a factor of ten. Make sure the price per kWh you enter matches where you are actually charging.
• Ignoring standing charges and peak/off-peak splits. Your bill also has a daily standing charge that does not change with how much you charge, and EV tariffs only give the cheap rate inside a set window. Charging outside that window costs much more.
• Assuming public prices apply everywhere. Quoting the motorway-services rate as your everyday cost is a common scare. If most of your charging is at home, your blended cost is far lower.
• Treating advertised range as real range. Cold weather, motorway speeds and a full car all cut range, which raises your real pence-per-mile figure above the showroom number.

These figures are estimates for general guidance only and are not personal tax or financial advice. Your actual cost depends on your tariff, your car and how you drive.

Related calculators

To build a full picture of your motoring and energy costs, try the fuel cost calculator to compare petrol or diesel, the cost per mile calculator to put EV and petrol on the same footing, and the energy bill calculator to see charging inside your wider household energy spend.