A rapid charge receipt, a home-energy bill and an annual insurance renewal do not look like parts of the same calculation. They are. EV expenses become misleading when each cost sits in a different app, bank transaction or kitchen drawer. The useful number is not a headline claiming that electric driving is cheap. It is what your car actually costs to run, for your tariff, routes, mileage and ownership pattern.
That requires a record which is detailed enough to be honest, but simple enough to keep while standing at a charger in the rain. If a cost is only logged when you get home, it is often not logged at all.
EV expenses are more than electricity
Electricity is the most visible running cost, so it usually gets the most attention. Yet it is only one part of the picture. A proper EV cost record separates energy costs from routine running costs and from the wider cost of ownership. That distinction matters because each answer serves a different purpose.
Energy-only cost per mile answers a straightforward driving question: what did it cost to power the car? It is useful for comparing home charging with public charging, checking whether a new tariff is worthwhile, or seeing how a long motorway trip affected the month.
Running cost per mile adds the items that keep the car legally on the road and in working order. Think insurance, servicing, tyres, MOTs where applicable, screenwash, parking and repairs. Total cost of ownership goes further, including finance interest, depreciation, road tax and any other ownership costs you choose to record. None is the one true figure. They are different views of the same vehicle ledger.
The mistake is to quote an energy-only figure as if it includes everything. A car may be inexpensive to charge but costly to insure, or it may have low monthly energy spend while carrying a large depreciation cost. Both things can be true.
The charging costs that distort the numbers
A home charge can look cheaper than it really was if you only log the amount paid at the socket and ignore a standing charge you would not otherwise have incurred. It can also look more expensive than it needs to if you allocate your entire domestic electricity bill to the car. The sensible treatment depends on your situation.
For most drivers, the clearest approach is to log the energy delivered to the car and the applicable unit rate, then keep tariff-specific costs visible where relevant. If an EV tariff gives you a low overnight rate that you genuinely use for charging, record that rate. If you regularly charge outside the cheap window, record the higher rate too. A blended home rate is useful only when it reflects what you actually pay.
Public charging needs equally careful treatment. A receipt may show kWh, price per kWh, connection fees, idle fees, VAT and a total. Capture all of it. The price printed on a charger screen is not always the final cost, particularly where a session runs into an overstay charge or a pre-authorisation hold confuses the card transaction.
Charging losses are another judgement call. If you track electricity bought from the wall and mileage travelled, your cost per mile already reflects those losses. If you compare the car’s dashboard consumption against your bill, the difference can be revealing, but do not count it twice. Choose a consistent method and keep it throughout the year.
Prepaid charging balances deserve their own record
A £100 charging credit is not the same as £100 of charging used. It is cash paid in advance for a future service. Recording the purchase as an expense immediately can make one month look needlessly expensive and the following months artificially cheap.
Instead, keep the prepaid block as a balance, then reduce it as charging sessions are used. This shows the remaining value, the effective rate and the actual burn rate. It also makes it easier to spot credit that is about to expire or a network that has become poor value after a tariff change.
The same principle can apply to workplace charging allowances, marina shore-power arrangements and other account-based energy schemes. Track what was paid, what was consumed and what remains. Guesswork is not a financial record.
Mileage turns spending into a usable figure
A monthly electricity total tells you something. Cost per mile tells you whether that spend is moving in the right direction. It makes different periods comparable, even if one month included a holiday trip and another was mostly school runs and local errands.
Log the odometer regularly, rather than relying on a rough annual mileage estimate. A photo of the dashboard is often enough. Then each charging cost and operating expense can be allocated against a real distance travelled.
This also prevents a common false comparison with petrol. The fair comparison is not against the price of petrol remembered from six months ago. Set a petrol baseline using a current fuel price and realistic mpg for the alternative vehicle. If fuel is £1.50 per litre and the comparable petrol car returns 40 mpg, its fuel cost per mile is very different from a claim based on an optimistic brochure figure.
Your savings then become evidence-based. They can rise when you charge at home on an off-peak tariff and fall when a month involves frequent rapid charging. That is not bad news. It is a true account of the way the vehicle was used.
Track maintenance before it becomes a surprise
EVs have fewer routine mechanical service items than many combustion cars, but they are not maintenance-free. Tyres, brakes, suspension components, air-conditioning servicing, alignment, wipers and 12V batteries still cost money. Some costs arrive infrequently, which is why they are easy to forget when someone asks what the car costs per mile.
A £900 tyre replacement should not vanish into a bank statement under a generic garage payment. Log the date, mileage, supplier, category, amount and receipt. The same applies to annual insurance, vehicle excise duty, breakdown cover and servicing plans.
There is a useful trade-off here. You do not need to turn every windscreen-washer top-up into an accounting project if that makes the record impossible to maintain. Track the categories that materially affect your decision-making, and use a consistent threshold for minor purchases. The aim is accuracy that survives real life, not a perfect spreadsheet abandoned in February.
Keep EV expense records ready for tax and work use
For self-employed drivers and small businesses, a clean log is more than a budgeting tool. It provides evidence of business mileage, charging expenditure and vehicle-related costs. The right treatment depends on ownership, VAT status, whether electricity is supplied at home or on the road, and whether the vehicle is used privately as well as for work.
That is precisely why the raw record matters. Keep the original receipt where possible, note VAT separately when it is shown, and record the journey or mileage purpose when business use needs to be evidenced. An accountant can apply the correct tax treatment far more easily when the underlying information is complete.
Do not assume every VAT amount is reclaimable, or that a public charging receipt automatically proves the right to reclaim it. The rules can depend on who incurred the cost and how the vehicle is used. A well-organised record does not replace professional advice, but it gives your accountant something defensible to work with.
A mobile-first logbook such as Amperlo is designed for this practical job: record a charge, receipt or mileage entry while it is fresh, then use the resulting ledger to see costs, VAT splits and reports without rebuilding the year from bank statements.
Use the figures to make decisions, not claims
Once you have several months of clean data, the patterns become more valuable than any single charging session. You may find that home charging accounts for most miles but public charging accounts for most energy spend. You may see a tariff saving disappear because charging has shifted outside its off-peak window. Or a higher insurance renewal may outweigh a fall in energy costs.
Use those findings carefully. A single winter month is not a verdict on the car, and neither is a summer road trip dominated by rapid charging. Compare similar periods, look at a rolling average, and keep energy-only and total-cost views separate.
The strongest EV cost record is not the one that produces the lowest number. It is the one you can explain. Start with the next charge, the current odometer reading and the next receipt. Small, timely entries are what turn scattered payments into an honest view of what your car actually costs to run.
