EV Efficiency Calculator

Find out how efficient your electric vehicle really is. Enter your battery capacity, the state of charge (SOC) at the start and end of a trip, and the distance you drove — the calculator works out the energy used and your average efficiency in km/kWh, mi/kWh, kWh/100km or Wh/km.

EV Efficiency Calculator
Work out your average efficiency from a single trip.
Energy used—kWh
Efficiency—km/kWh
Consumption—kWh/km

Share this calculation — the link prefills your values.

How to measure your EV’s efficiency

  1. Step 1

    Note your state of charge before you set off — or charge to a round figure like 80% to make the maths easy.

  2. Step 2

    Drive your normal trip, then record the ending SOC and the distance covered from the trip computer.

  3. Step 3

    Enter the numbers above to get energy used (kWh), distance per kWh and consumption per kilometre or mile.

The efficiency formula

The calculator first works out how much energy the trip consumed:energy used = battery capacity × (start SOC − end SOC) ÷ 100. A 60 kWh battery dropping from 100% to 40% uses 36 kWh. Dividing the distance travelled by that energy gives your efficiency — for example 250 km on 36 kWh is 6.9 km/kWh, or 14.4 kWh/100km the other way up.

Not sure which unit to quote the result in? Our EV efficiency converter translates any figure between Wh/km, kWh/100km, km/kWh, Wh/mi, mi/kWh and kWh/100mi instantly, and the guide what is EV efficiency?explains what a good number looks like for your class of car.

Why your real-world efficiency matters

Official EPA and WLTP figures are measured in labs on gentle cycles. Your own efficiency — measured over your roads, your speeds and your weather — is the only number that reliably predicts how far your car will go. Feed it into the EV range calculator to plan charging stops with confidence, and track it over time to spot winter losses, tyre problems or roof-box drag before they cost you.

Frequently asked questions

What is a good efficiency for an electric car?

Most modern EVs achieve between 14 and 20 kWh/100km (155–200 Wh/km, or roughly 3.1–4.4 mi/kWh) in mixed real-world driving. Efficient hatchbacks and saloons can beat 15 kWh/100km (over 4 mi/kWh), while large SUVs and vans often sit above 22 kWh/100km. Weather, speed and terrain all move the figure, so compare like for like.

Why is my EV efficiency worse in winter?

Cold weather thickens the battery's internal chemistry, reduces regenerative braking and demands energy for cabin and battery heating. Most drivers see consumption rise 10–30% in freezing conditions. Preconditioning the car while plugged in and using heated seats instead of the cabin heater softens the drop.

Should I measure efficiency in kWh/100km or mi/kWh?

Use whichever your car and region use. Europe typically quotes kWh/100km or Wh/km (lower is better), while North America prefers mi/kWh (higher is better). They are reciprocals of each other — our efficiency unit converter translates between all of them instantly.

Can I use this calculator for a plug-in hybrid (PHEV)?

Yes, as long as the trip was driven in electric-only mode. Enter the usable battery capacity, the state of charge at the start and end of the electric drive, and the electric distance covered.

Can I share my efficiency calculation?

Yes. Hit the Share button and the resulting link carries all your values as URL parameters. Anyone who opens it sees your numbers prefilled and the result already calculated — nothing is stored or sent to a server.

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