# Calculating your EV's consumption: kWh per 100 km

> How to work out your electric car's real consumption from your odometer and charging meter, what affects it, and how to estimate trip costs and range.

Published: 2026-10-13 · Language: en · Source: https://laadpaalvinden.be/en/blog/calculate-ev-consumption-kwh-100km/

The consumption figure a manufacturer quotes rarely matches what you get on the road. It depends on where you drive, how fast and in what weather. Your own figure is more useful, and all you need is an odometer and a bit of arithmetic.

## The basic formula

Divide the energy used in kWh by the distance driven in kilometres, then multiply by 100. If you drove 500 km and used 90 kWh, your consumption is 90 / 500 x 100 = 18 kWh per 100 km.

The hard part is knowing where those 90 kWh come from. There are two sources.

## Trip computer or charging meter?

The trip computer shows the energy that leaves the battery. That is what the car actually uses. What you measure at the charger or wallbox is higher, because some of the electricity is lost as heat during charging. How much depends on the car and the charger. If you want to know what a trip costs you, the kWh you pay for matter most. If you want to compare cars or driving styles, the trip computer is the better choice.

Pick one source and stick with it. Mixing figures from both gives an average that means nothing.

## How to measure with your charging meter

1. Charge up and note your odometer reading and the battery percentage.
2. Drive as you normally do. Charge along the way as usual and keep track of the kWh from your app or your wallbox meter.
3. After a few weeks, note the odometer and battery percentage again.
4. Add up the kWh charged and adjust for the difference in battery level.

A worked example. You drove 1,200 km and charged 228 kWh at home according to the meter. You started at 80% and ended at 60%. Say your battery has 60 kWh of usable capacity: that 20% difference is 12 kWh you took out of the battery without recharging. Your total is 240 kWh. That gives 240 / 1,200 x 100 = 20 kWh per 100 km. Without that correction you would have calculated 19.

Look up the usable battery capacity in your car's documentation. If you also charge in public, include those sessions.

## What affects your consumption?

- Speed: the faster you go, the more air resistance you fight.
- Temperature, as covered in [winter range and charging](/en/blog/ev-winter-range-and-charging/). Heating and a cold battery cost energy.
- Tyre pressure and tyre type.
- Weight, roof boxes and trailers.
- Driving style and hills. Going uphill costs energy, going downhill gives some back.
- Short trips, where the car has to warm up every time.

That is why a single trip tells you little. An average over a few weeks and different conditions is far more reliable. To see the seasonal effect, calculate your consumption separately for summer and winter.

## What do you do with the figure?

First, the cost of a trip. Take a consumption of 19 kWh per 100 km and a price of 0.30 euro per kWh. That is 5.70 euro per 100 km. For a 250 km trip you need 47.5 kWh and pay 14.25 euro. These are example figures: enter your own consumption and your own tariff. The price per kWh at home, at a public AC charger and at a fast charger often differs a lot.

You can also estimate your range. If your battery has 60 kWh usable and you use 18 kWh per 100 km, you get 60 / 18 x 100 = just over 330 km. If you use 22 kWh in winter, that drops to around 270 km. For a long trip, plan with your worst consumption, not your best, and leave a margin for a detour or an occupied charger.

## When is your figure wrong?

- You measured only one trip, or only motorway trips, or only city trips.
- You left out a public charging session, or a top-up at a friend's or at work.
- You forgot the difference in battery percentage between start and finish.
- You mixed trip computer and charging meter figures.
- You drive with a trailer or a full roof box. That is a separate consumption, so note it separately.

The [charging calculator](/en/charging-calculator/) works out the cost straight away from your consumption and tariff. To see how that compares with a petrol or diesel car, read [EV running costs versus petrol and diesel](/en/blog/ev-vs-petrol-diesel-running-costs/).