Separate the battery top-up from the electricity bill
A charger bills energy from its meter, while the battery stores energy after losses. For a 60 kWh usable battery charged from 20% to 80%, the battery gain is 36 kWh. With an illustrative assumption that 10% of grid energy does not reach the battery, billed energy is 36 ÷ 0.90 = 40 kWh.
Here the loss percentage is a share of grid energy, not an extra percentage added to battery energy. Multiplying 36 by 1.10 would give 39.6 kWh and use a different definition. Use your own evidence for losses when available; 10% is an example assumption, not a universal measured rate.
Price the session with the tariff you will actually pay
At an illustrative £0.25/kWh, that 40 kWh session costs £10. At £0.65/kWh, it costs £26 before additional fees. Neither price is a current supplier offer. Check the station or electricity contract before copying a price into a calculator.
Include connection, parking, idle and subscription fees where they apply. Confirm whether the price already includes tax. If charging crosses two time bands, allocate the billed energy to each band rather than applying the cheap rate to the entire session. Currency selection changes the displayed denomination; it does not convert prices.
Calculate a monthly budget from distance
Suppose you drive 1,000 km per month at 18 kWh/100 km. The car uses 180 kWh for those journeys. With the same 10% grid-loss assumption, charging requires 200 kWh. The table holds consumption and losses constant so that only the charging-price mix changes.
The mix is a share of billed energy, not a share of charging visits. One long rapid charge may buy more energy than several short home top-ups. Use the energy shown on bills or receipts to estimate the mix.
| Where the 200 kWh is bought | Monthly cost | Per 100 km |
|---|---|---|
| All at home: £0.25/kWh | £50 | £5.00 |
| 70% home at £0.25; 30% public at £0.65 | £74 | £7.40 |
| All public: £0.65/kWh | £130 | £13.00 |
Find the subscription break-even before subscribing
Imagine a charging plan with a £10 monthly fee and an eligible energy-price reduction from £0.65 to £0.50/kWh. The saving is £0.15 per eligible kWh, so the fee is recovered at £10 ÷ £0.15 = 66.7 kWh per month. Buying 60 kWh saves £9 before the fee and costs £1 more overall; buying 100 kWh saves £15 before the fee and £5 overall.
Count only energy bought on the plan’s eligible network and rate. Check roaming prices, minimum terms and whether a second vehicle can use the account. A subscription can make sense in a busy travel month and be unnecessary in a month dominated by home charging.
Check the household tariff as well as the car tariff
A cheap overnight EV rate can be accompanied by a different daytime rate or standing charge. Compare the whole bill. In a purely illustrative month, saving £15 on charging but paying £12 more for daytime household electricity leaves £3, before any standing-charge difference.
For a new wallbox, compare a written installation quote with the savings you can realistically achieve. A £900 installation divided by £30 monthly charging savings gives a simple 30-month payback. It excludes finance, repairs and future tariff changes. If installation is already paid for, treat it separately from the decision about where to buy tonight’s electricity.
Use each EVVerity tool for its specific question
Use Charging Cost for a battery top-up and energy cost per distance. Enter annual distance to calculate the monthly average; 1,000 km/month means 12,000 km/year. Use Charging Tariff Comparison for an energy mix, a subscription and simple charger payback. Use Cost of Ownership when you also need insurance, tax, maintenance, finance and depreciation.
Re-run the budget with a higher public-charging share and less favourable consumption. If a small change removes the expected saving, the result is sensitive to your charging routine. That is useful information to establish before buying the car, especially when home charging is uncertain.
Put the explanation to work
Use your own vehicle information, check the assumptions and see the calculation.
Charging Cost →EVVerity estimates are informational and are not a substitute for a professional battery diagnostic or pre-purchase vehicle inspection.
Sources & editorial basis
Source list reviewed 2026-10-26. Additional guidance carries its own review date. Practical checklists and worked examples are EVVerity editorial guidance. Read our methodology.
Related reading
- Owning an EV without home charging
- Compare home charger installation quotes
- Convert kWh/100 km, miles/kWh and Wh/mile
Apply this to a model
Check the model’s battery references, charging equipment and viewing checklist. Match the year and original market to the car you are considering.