MilometryCharging an electric car
How to log a charge, what the tariff book does, and how battery readings give you a real efficiency figure without ever charging to 100%.
General information, not advice. Written as general information and correct as far as we know on 15 October 2026. Tax rules change, and how they apply depends on your own circumstances. This is not tax, legal or financial advice: check with an accountant, a tax adviser or HMRC before you rely on it.
An electric or plug-in hybrid car is costed the way a petrol car is: an efficiency figure times a price. The difference is where the figures come from. A petrol car has one price and fills to full; an electric car has a home tariff, often a cheaper one at night, a work rate and public chargers at several times either, and most owners never charge to 100%. This page covers the three things that deal with that: the charge screen, the tariff book, and battery readings.
Log a charge once you have plugged in or unplugged, never while driving.
1. Tell Milometry what the car runs on
Open Settings → Vehicles, pick the car, and under Fuel type choose Electric or Plug-in hybrid. A self-charging hybrid stays Hybrid: it only ever takes fuel.
Two more fields appear:
- Electric efficiency, in mi/kWh (or kWh/100 km on a metric scheme). Put the maker's figure in to start with; it is replaced by a measured one as soon as there is one.
- Battery size (kWh), the usable capacity. This is what turns battery readings into a measurement, in step 5.
The first-run setup asks the same questions, so a car set up as electric from the start is ready.
2. Open the charge screen
The same two ways in as a fill-up: the notebook button on the Track tab, then Log a charge, or Settings → Fuel & charging and the + button. For an electric car the screen is Log a charge. For a plug-in hybrid it is Log fuel or a charge, with Fuel and Charge buttons at the top.
3. kWh, cost and where you plugged in
- kWh added: what the charger or the car reports, for example 42.
- Where you charged: Home, Work or Public.
- Total cost: fills itself in from the tariff book (step 4) as soon as the kWh are typed, and says which tariff it used. Type over it if the receipt says otherwise.
Underneath, the price per kWh is worked out for you. The Odometer and Charger fields work exactly as the station field does for a fill-up, pin on the map included.
4. The tariff book
On Settings → Fuel & charging, the Electricity tariffs card holds four rates: Home, Home off-peak with the hours it runs, Work and Public. Each saves when you leave the field. A charge in the off-peak window prices itself at the off-peak rate; a daytime top-up at home uses the day rate and never overwrites the night one.
Every journey is costed at your cheapest home rate, then home, then work. A public rapid charge is logged and counted in what you spent, but it is never the price your year's driving is costed at: a motorway charger is not what the car usually costs you.
Each charge you log teaches the book the rate for where you charged, so after the first few the fields look after themselves.
5. Battery readings
Battery before (%) and Battery after (%) are the figures on the dash as you plug in and unplug. Both are optional, but with the battery size set they are the fields that matter most, for the same reason the odometer matters on a fill-up.
With both readings on two consecutive charges, plus an odometer reading on each, Milometry knows how much energy the car used between them (the drop from one charge's "after" to the next's "before", as a share of the battery) and how far it went. That is a real efficiency figure, and it needs no charge to 100%. The top of the fuel screen then says what a full battery is worth in miles at that efficiency.
If a charge starts with more battery than the previous one left, a charge went in that nobody logged. The fuel screen says so, the way Insights flags unlogged miles from odometer gaps.
6. Charged to full
Without battery readings, efficiency is measured the old way: between two charges to full with odometer readings, with any top-ups in between folded in. Charged to full marks one, and a reading of 100% after counts as full whatever the switch says.
7. Where the figures turn up
- The Track tab shows Est. energy while you drive an electric car.
- Each trip shows the estimated kWh and cost, and says whether it was costed at a measured or a stated efficiency.
- Insights adds charging to the fuel figure, draws the efficiency line for an electric car, and counts CO₂ for electricity at the grid's generation rate rather than as zero.
- The fill-ups CSV carries every charge with its kWh, price per kWh, location and both readings, and the claim PDF names each trip's energy.
Charges stay on your phone with everything else. Looking up a charger's name sends the pin's position to Apple or Google, as it does for a petrol station, and nothing more.
