What is EV Efficiency? kWh per 100km Explained

EV efficiency is a measure of how much electrical energy an electric vehicle consumes to travel a given distance. It is expressed in kilowatt-hours per 100 kilometres — written as kWh/100km. A lower number means the car uses less energy per kilometre and is more efficient. Unlike range, which tells you how far you can go, efficiency tells you how well your car uses every unit of energy to get there.

Understanding your EV's efficiency is more useful than knowing its range — because efficiency is something you can actively improve, and because it gives you a consistent benchmark across conditions, routes, and vehicles.

kWh/100km vs miles per kWh: what's the difference?

There are two common ways to measure EV efficiency, depending on where you are in the world:

• kWh/100km — used in Europe and most of the world. Lower is better. Equivalent to fuel consumption (litres/100km) for petrol cars.
• Miles per kWh (mi/kWh) — used in the United States and UK. Higher is better. Equivalent to miles per gallon.

To convert: divide 100 by your kWh/100km figure to get approximate kWh per 100km in mi/kWh terms, or use the conversion factor of 1.609. A car doing 16 kWh/100km is doing roughly 3.9 miles per kWh.

This guide uses kWh/100km throughout.

What is a good EV efficiency score?

Efficiency varies significantly by vehicle size, weight, and aerodynamics. As a general benchmark for real-world mixed driving:

• Under 15 kWh/100km: Excellent — compact, aerodynamic, or very efficiently driven
• 15–18 kWh/100km: Good — typical for mid-size EVs like the VW ID.3, Polestar 2, or Tesla Model 3
• 18–22 kWh/100km: Average — common for larger cars and SUVs like the Tesla Model Y or BMW iX3
• 22–28 kWh/100km: Below average — larger vehicles, performance models, or inefficient driving conditions
• Above 28 kWh/100km: Poor — large SUVs, high-performance modes, or extreme weather impact

These ranges are for real-world driving. Manufacturer WLTP ratings are typically 10–20% better than what you'll see in everyday use.

Why efficiency matters more than range

Range is the number manufacturers advertise. Efficiency is the number that actually determines your experience.

Two cars can have identical 450 km WLTP ranges but behave very differently. A car with 15 kWh/100km that degrades slightly in cold weather will still comfortably cover 350 km in winter. A car with 22 kWh/100km and the same range rating will struggle.

Efficiency is also what you can improve through your driving behaviour. Range is fixed by the battery. Efficiency is variable — and understanding what drives it is the first step to getting more out of every charge.

What affects EV efficiency?

1. Speed — the biggest single factor

Aerodynamic drag increases with the square of speed. This means driving at 130 km/h uses roughly four times the aerodynamic energy of driving at 65 km/h. Motorway driving is consistently the most energy-intensive environment for an EV — the opposite of petrol cars, which are most efficient at steady highway speeds.

Most EVs hit their efficiency sweet spot between 80–100 km/h. Above that, consumption rises sharply.

2. Temperature — especially cold

Cold weather is the most significant real-world efficiency variable most drivers encounter. At sub-zero temperatures, an EV's battery must work harder to maintain optimal operating temperature, and the cabin heating system draws directly from the battery. Range and efficiency losses of 20–40% in very cold conditions are commonly reported by EV drivers.

Heat pumps — now standard on many newer EVs — significantly reduce this penalty by using ambient heat more efficiently than resistive heating.

3. Heating and air conditioning

Climate control is one of the largest draws on EV battery capacity after propulsion. Running a cabin heater in winter can consume 2–5 kWh per hour, meaningfully impacting short to medium journeys. Pre-conditioning the cabin while plugged in — available on most EVs — avoids this drain entirely.

4. Driving style

Smooth, anticipatory driving — accelerating gently and coasting early to regenerate — consistently outperforms aggressive stop-start patterns. Regenerative braking recovers energy on deceleration, but it is always less efficient than not needing to brake in the first place. The most efficient EV drivers use one-pedal driving and plan their stopping well in advance.

5. Weight and load

Every additional 100 kg increases energy consumption. Full passenger loads, roof boxes, and heavy cargo all reduce efficiency — the same as in any vehicle, but with more directly visible data in an EV context.

6. Tyre pressure

Under-inflated tyres increase rolling resistance, which directly increases energy consumption. Keeping tyres at the manufacturer's recommended pressure — or slightly above — is one of the easiest efficiency improvements available to any EV driver.

WLTP vs real-world efficiency: why the gap exists

WLTP (Worldwide Harmonised Light Vehicle Test Procedure) is the European standard for measuring EV energy consumption and range. It replaced the older, less realistic NEDC cycle and is more representative of real driving — but it still cannot capture all variables.

WLTP tests are conducted at moderate temperatures (23°C), with no accessories running, and on a standardised drive cycle. Real driving adds cold weather, heating, motorway speeds, and stop-start traffic in combinations that the test does not model.

The result is that most drivers experience real-world efficiency 10–25% worse than the WLTP figure, depending on climate and driving patterns. In very cold climates, the gap can be larger.

How to improve your EV efficiency

1. Drive at 90–100 km/h on motorways where possible — the efficiency gain over 120 km/h is significant
2. Pre-condition while plugged in — heat or cool the cabin before unplugging, not after
3. Use regenerative braking — set it to maximum and practice one-pedal driving
4. Check tyre pressure monthly — especially before long journeys or as seasons change
5. Reduce unnecessary weight — remove roof boxes and heavy items when not in use
6. Track your consumption over time — patterns across seasons and routes reveal exactly where you're losing efficiency

The last point is where data becomes genuinely useful. A single trip's efficiency is interesting. Months of data, across conditions, compared with other drivers in similar vehicles on similar routes — that is where real insights emerge.

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