A kilowatt-hour is measured, not estimated: a meter continuously multiplies the voltage and current passing through it to get power in kilowatts, then adds that power up over time. One kilowatt flowing for one hour is one kilowatt-hour. Which meter counts depends on where you charge — the utility meter bills home charging, the charger’s internal meter is what a per-kWh public bill is based on, and your car’s display is a third figure: an estimate of what the battery stored.
Key Takeaways
- A kilowatt-hour is power multiplied by time, counted by a meter — 1 kW for one hour.
- Home charging is billed by the utility meter; a per-kWh public bill is based on the charger’s own certified meter.
- Your car displays an estimate of energy stored, which is always lower than the energy delivered — the gap is charging losses.
- The charger’s session record is the evidence if a bill looks wrong.
Three Counters, Three Different Jobs
Every session passes several counters, and they disagree by design: each measures at a different point in the chain.
| Counter | Where it measures | What it is used for |
|---|---|---|
| Utility meter | Where electricity enters your home | Billing everything the house draws, charging included — counted before the charger converts it. |
| Charger’s internal meter | Inside the wallbox or public charger | The session record — energy delivered through the cable; the figure a per-kWh public bill is based on. |
| Car’s own estimate | At the battery, via the battery management system | Dashboard percentage and stored-energy figures. An estimate of what was kept, not a billing meter. |
The three figures never agree exactly, and they are not supposed to: energy is lost as heat between the charger and the battery, so each counter downstream reads lower. Worked example, with invented numbers to show the arithmetic only: a session delivers 40 kWh at the charger; if 4 kWh turns into heat on the way in, the car stores 36 kWh, and its display works from the 36. For typical session sizes, see how many kWh it takes to charge an EV.
The Meter Behind a Bill Is a Certified One
Where money changes hands per kilowatt-hour, the counter stops being a convenience display. In regulated markets, a meter used for billing must be a certified, sealed measuring device — the same principle as a petrol pump’s meter — whose accuracy the operator can be required to have checked. A public session therefore produces a formal record: the meter’s start and end readings are what your receipt, and any dispute, is built on.
The same logic is why your home bill follows the utility meter rather than your wallbox. The wallbox counter is for your own tracking — separating the car’s energy from the rest of the house — but the certified meter on the supply is the one the bill is built from. Your car’s figure, by contrast, is computed from battery voltage, current and temperature to manage the pack: modelled, rounded, and never a billing instrument.
How to Sanity-Check a Session Figure
- Compare the session kWh with the charge you added: the percentage gained, applied to your battery’s usable size, should land a little below the billed figure — the difference is losses.
- At home, the app shows the charger’s counter while your bill follows the utility meter, which also counts the rest of the house. The totals will never match exactly.
- If a public session claims more energy than your battery could hold, query it with the operator, with the receipt as evidence.
Chargers That Keep the Records
Per-session metering is why connected chargers log every session. The EVDANCE EV-ACT3204PE 22 kW wallbox (RFID and app, CE) reports each session’s energy in its app, so a household can separate car energy from the rest of the bill. For shared sites, the EV-AC03201T dual-connector AC station (OCPP 1.6J, RFID) sends session records to the operator’s platform — what itemised billing and reimbursement are built from. On smart meters, see do you need a smart meter for an EV charger?
Frequently Asked Questions
Which meter decides what I pay at a public charger?
The charger’s internal meter, where you are billed per kilowatt-hour. It measures the energy delivered through the cable, and that session record is what appears on your receipt.
Is the kWh figure in my home charging app the one on my electricity bill?
Not exactly. Your bill is built from the utility meter, which counts everything the house draws. The app counts only what passed through the charger — the car’s share, but never the bill itself.
Can a charger’s meter be wrong?
Meters used for billing are certified and sealed in regulated markets, and operators can have them checked. If a figure looks impossible for your battery’s size, raise it with the operator.
Related Reading
- Do You Need a Smart Meter for an EV Charger?
- How Many kWh Does It Take to Charge an EV?
- How Do EV Charging Stations Work?
