How to calculate EV charging cost per kWh

An EV charging session costs the energy taken from the grid multiplied by your price per kWh, plus any fee caused by that session. Battery energy and grid energy are not interchangeable: conversion losses mean the meter can record more kWh than the battery receives. This guide shows the calculation for the UK, Germany and the Netherlands; the charging cost calculator is where you can run and edit your own scenario.

At a glance

• Battery energy: E_bat = usable capacity × (final SOC − initial SOC).
• Grid energy: E_grid = E_bat ÷ efficiency. Efficiency is an editable assumption, not a universal loss percentage.
• Variable cost: grid kWh × tariff per kWh.
• Session total: variable cost plus only a fee that you actually incur because of this session.
• Official examples: the figures below are dated reference snapshots for defined domestic markets, not universal current tariffs and not public-charging prices.
• Reviewed: 24-08-2026. Sources were accessed on the same date.

Start with the energy going into the battery

Battery energy for a partial charge comes from usable capacity and the change in state of charge, or SOC. Enter SOC percentages as fractions in the formula: 20% is 0.20, while 80% is 0.80.

E_bat = C_usable × (SOC_final − SOC_initial)

C_usable means the usable battery capacity in kWh, not an unlabelled gross figure. Use the value supplied for your vehicle or your own known input; the calculation cannot infer it safely from a model name. The distinction matters because a percentage is applied to the capacity you enter.

A reproducible example uses a usable capacity of 60 kWh and a charge from 20% to 80%:

E_bat = 60 × (0.80 − 0.20) = 36 kWh

The battery therefore gains 36 kWh. This is an energy quantity. A tariff written as £/kWh or €/kWh tells you the price of each unit of grid energy; it does not tell you how quickly the car charges.

Convert battery energy into grid energy

Grid energy is higher than battery energy whenever charging efficiency is below 100%. The relevant efficiency, eta, is the share of energy taken from the grid that is stored in the battery. Losses can occur in the cable, conversion equipment, battery and auxiliary systems, and they vary with the equipment and conditions.

E_grid = E_bat ÷ eta

For the worked example, 85% efficiency (eta = 0.85) is only an editable EU modelling assumption. It is not a measurement of a particular vehicle, charger, home or country. The European Commission has used 85% as a fleet-level modelling assumption and explicitly notes variation between vehicles.

E_grid = 36 ÷ 0.85 = 42.3529... kWh

Keep the full value while calculating and round only the displayed result: 42.35 kWh. If your meter, charger or receipt already reports grid energy, use that measured number directly. Dividing it by efficiency again would count the losses twice.

Read the price per kWh before multiplying

The correct tariff is the unit price that applies to the session you are calculating. For home charging, copy the applicable energy unit rate from your contract or bill. A domestic standing charge that you already pay regardless of the car is not an incremental session cost, so it should not be allocated to every charge by default.

Public charging needs a different input. Use the operator's displayed per-kWh rate and add any session-specific amount shown in its terms or receipt. There is no single national public-charging price for the UK, Germany or the Netherlands, and the domestic reference values below must not be substituted for one.

Market	Dated official reference	Scope and expiry	What it must not be called
Great Britain	£0.2611/kWh	Ofgem average standard variable direct-debit unit rate, including 5% VAT, for England, Scotland and Wales from 01-07-2026 to 30-09-2026; it expires after that period	Your tariff, a Northern Ireland rate or a public-charging price
Germany	€0.4055/kWh	Destatis total household average for 2025 H2, including taxes, levies and surcharges; a historical statistical benchmark	An August 2026 price, a wallbox tariff or an offer
Netherlands	€0.25055/kWh	CBS marginal example for June 2026: €0.13970 supply with VAT plus €0.11085 electricity tax with VAT; excludes annual network/supply charges and the annual tax reduction	A total bill, a dynamic tariff or a public-charging price

The Ofgem snapshot does not cover Northern Ireland and expires on 30-09-2026. The German figure describes all household consumption classes in 2025 H2. The Dutch figure is a June 2026 weighted consumer reference for fixed and variable contracts, assembled only from the two stated marginal components. In every case, replace the example with the rate that actually applies to you.

Calculate one session in three markets

The cost formula uses grid energy, not battery energy:

variable_energy_cost = E_grid × tariff_per_kWh
session_cost = variable_energy_cost + incremental_session_fee

Holding the battery inputs and the 85% scenario assumption constant makes the three calculations reproducible. The fee is set to zero so the table isolates energy cost.

Market example	Grid energy	Dated tariff input	Calculation	Illustrative energy cost
Great Britain	42.3529 kWh	£0.2611/kWh	42.3529 × 0.2611	£11.06
Germany	42.3529 kWh	€0.4055/kWh	42.3529 × 0.4055	€17.17
Netherlands	42.3529 kWh	€0.25055/kWh	42.3529 × 0.25055	€10.61

These are three applications of one method, not a ranking of tariffs or a promise about a future bill. The geography and period attached to each input remain part of the result. Changing the language of this guide does not turn an Ofgem reference into a German or Dutch tariff.

See how an efficiency assumption changes the result

Cost changes in direct proportion to the tariff and grid energy. For the same 36 kWh added to the battery, a lower efficiency assumption produces more purchased energy because the calculation uses 36 ÷ eta.

Scenario efficiency	Grid energy	UK reference	German reference	Dutch reference
95%	37.89 kWh	£9.89	€15.37	€9.49
90%	40.00 kWh	£10.44	€16.22	€10.02
85%	42.35 kWh	£11.06	€17.17	€10.61
80%	45.00 kWh	£11.75	€18.25	€11.27

The 80–95% rows are sensitivity scenarios, not a claimed normal range. A measured grid value takes precedence. Keeping eta visible also makes the estimate auditable: another reader can reproduce it, replace the assumption and see exactly why the result changes.

Add only genuinely incremental charges

A per-session activation fee belongs in the total when the operator actually charges it for that session. The same principle applies to another amount that appears solely because you initiated or used that charge. Enter the amount as a separate input rather than hiding it inside the energy price.

Item	Include in this session?	Treatment
Energy unit rate	Yes	Multiply by measured or calculated grid kWh
Actual per-session fee	Yes	Add once after the variable energy cost
Actual incremental operator charge	Yes	Add the amount attributable to this session, using the operator's terms or receipt
Existing domestic standing charge	No by default	Do not assign it again when the household pays it without charging the car
Annual network or supply charge	No by default	Keep outside a session unless it is a new incremental cost and you deliberately model another scope
Charger installation or vehicle ownership cost	No	These are outside this session-energy method

This separation prevents a common category error. A session calculation answers “what did this energy event cost under these inputs?” It does not calculate installation cost, ownership cost, payback or savings.

A repeatable five-step check

1. Choose the energy basis. Use measured grid kWh when available; otherwise calculate battery energy from usable capacity and SOC.
2. State the efficiency input. Divide battery energy by an editable eta once, and label whether it is measured or assumed.
3. Copy the applicable unit rate. Record its currency, market, tariff type and validity period.
4. Add incremental fees separately. Use only amounts the session actually triggers.
5. Preserve the inputs. Report battery kWh, grid kWh, tariff, efficiency, fee and date with the total so another person can reproduce it.

The most frequent mistakes are using gross capacity without saying so, treating 20 as 20 rather than 0.20, applying losses to an already measured grid value, using a dated national snapshot as a universal current price, or adding the same domestic fixed charge to every session. Each mistake changes the question being answered.

Run your own numbers

Use the EV charging cost calculator to change market, usable battery capacity, SOC, efficiency, tariff and incremental fee. The tool executes scenarios; this guide remains the audit trail for the method. If you also need an AC duration estimate, open the charging time calculator. You can review all available calculators, browse the guide library, or read the site's editorial and source methodology.

Official sources and review date

• Battery-energy terminology: Regulation (EU) 2023/1542, accessed 24-08-2026.
• Efficiency definition and variation: European Commission JRC evaluation of fast-charging efficiency, published 28-08-2018 and accessed 24-08-2026; European Commission modelling document using the 85% scenario, accessed 24-08-2026.
• Great Britain snapshot: Ofgem unit rates and standing charges and Ofgem's 01-07-2026 to 30-09-2026 price-cap notice, accessed 24-08-2026.
• Germany snapshot: Destatis GENESIS table 61243-0001, 2025 H2 data, table status 22-07-2026, accessed 24-08-2026.
• Netherlands snapshot: CBS table 85592NED, June 2026 components, accessed 24-08-2026.

Next review: replace or remove the Ofgem input after 30-09-2026; recheck the German reference when Destatis publishes a newer half-year and the Dutch reference monthly.