EV charging cost calculator (UK home charging)

How the EV charging calculation works

Two sums give the answer. First, the energy needed is the usable battery size multiplied by the share of the battery being filled. Second, that energy divided by the charging power gives the time, and multiplied by the unit price it gives the cost. If an optional loss figure is entered, the energy drawn from the meter is increased to cover it, and both the time and the cost use that larger figure.

A worked example: a car with a 60kWh usable battery charged from 20% to 80% takes on 60 x 0.6 = 36kWh. On a 7kW chargepoint that is 36 / 7 = 5.14 hours, about 5 hours 9 minutes. At the Ofgem price cap rate of 26.32p per kWh the electricity costs 36 x 26.32p = £9.48. The same charge from a 2.4kW three-pin socket would take 15 hours.

What changes the result

Charger power and your home's supply

Which? says 7.4kW is the most a typical single-phase UK home can supply and that a 7kW chargepoint suits most drivers. A 22kW charger needs a three-phase supply, which most homes do not have. Approved Document S sets a minimum of 7kW for chargepoints installed in new homes under the Building Regulations.

The car's own limit

A car can only accept AC power up to the limit of its on-board charger. Which? says this is likely to be 7kW to 11kW, or less for plug-in hybrids. Fitting a faster chargepoint than the car can use does not make it charge any faster, which is why the calculator uses the lower of the charger and car figures when both are entered.

Your tariff

The default is the price cap rate, a GB average for a single-rate Direct Debit tariff. Rates vary by region and supplier, and many EV drivers use time-of-use tariffs with a cheaper overnight rate. Because cost is energy multiplied by price, halving the rate halves the cost of the charge.

How full the battery is

Topping up from 50% to 80% needs half the energy of a 20% to 80% charge. Many drivers charge to a set limit for daily use and only charge fully before a long trip; the car's handbook gives the maker's advice for that model.

Common mistakes and tips

• Using the gross battery size. Enter the usable capacity, which is the figure that can actually be charged. It is usually listed in the car's specifications.
• Assuming a faster charger always helps. The car's AC limit and the home's supply both cap the speed.
• Forgetting the standing charge. The daily standing charge is paid whether or not the car is charged, so it is not part of the cost of a charge.
• Leaving the tariff unchecked. The unit rate on a recent bill or in the supplier's app gives a more accurate cost than the average.
• Planning around a three-pin socket. At about 2.4kW a large battery can take more than a day to fill, so a dedicated chargepoint is the practical choice for daily use.

When to get a professional

A home chargepoint runs on its own circuit and should be installed by a qualified electrician, who checks that the supply, the consumer unit and the earthing can take the extra load. If the house needs a supply upgrade, or the chargepoint has to go some distance from the meter, the electrician will explain the options and the cost before starting. Getting this right first time avoids tripping, overloaded circuits and a charger that cannot run at full speed.

How this is worked out

• Energy into the battery (kWh) = usable battery kWh x (target % minus start %) / 100.
• Energy from the meter (kWh) = energy into the battery / (1 minus losses % / 100). With losses at 0 the two are the same.
• Charging power (kW) = the charger power, or the car's AC limit if that is lower.
• Time (hours) = energy from the meter / charging power, assuming a steady rate.
• Cost (£) = energy from the meter x unit price in pence / 100.

• Ofgem, energy price cap unit rates and standing charges (1 October to 31 December 2026, checked 9 November 2026). GB average electricity unit rate of 26.32p per kWh and standing charge of 54.83p per day for Direct Debit on a single-rate tariff. Ofgem states there is no VAT on electricity from 1 October 2026 to 31 March 2027.
• Which?, electric car charging at home (20 October 2026, checked 9 November 2026). 7.4kW is the most a typical single-phase UK home can supply and 7kW suits most drivers; 22kW needs a three-phase supply; cars usually accept 7kW to 11kW on AC, less for plug-in hybrids; a 2.4kW three-pin socket takes at least 30 hours for a full charge depending on the car.
• HM Government, Approved Document S: infrastructure for the charging of electric vehicles (2021 edition, page updated 17 April 2023, checked 9 November 2026). Chargepoints required under the Building Regulations for new homes should have a minimum nominal rated output of 7kW.

Related guides

• Electric Car Charger Installation at Home Explained
• Does Your Home Need a Bigger Supply for an EV Charger?
• Can You Get a Home EV Charger Without a Driveway?