EV range explained in plain numbers

Electric cars are marketed with big battery numbers because they are easy to advertise. The harder number is consumption. Two cars with a similar battery can deliver very different real-world range if one needs far more Wh/km to move down the road.

The core formula: capacity and efficiency

Range comes down to one relationship: usable battery capacity divided by energy consumption. Expressed as an equation:

Range (km) = Usable capacity (kWh) / Consumption (kWh/km)

It is more common to see consumption expressed in Wh/km rather than kWh/km, so the same formula written in practical terms is: range = (usable kWh x 1000) / Wh/km.

A worked example makes this concrete. Take a car with a 64 kWh total pack. Manufacturers typically hold back 10 to 15 percent to protect cell chemistry, so the usable capacity is around 58 kWh. If that car averages 170 Wh/km on a mixed route, the real-world range is 58,000 / 170 = roughly 340 km. Clip the speed up to motorway pace and consumption rises to, say, 230 Wh/km. The same battery now yields 58,000 / 230 = about 250 km. That 90 km gap comes entirely from driving style and speed, with no change to the battery at all.

A 60 kWh usable pack at 170 Wh/km gives approximately 350 km. At 250 Wh/km it gives 240 km. The battery did not shrink; only the efficiency changed.

Why the WLTP or EPA figure rarely matches real life

Official range figures are measured on a test cycle, not on real roads. The WLTP (used in Europe) runs at moderate speeds, with minimal climate control and on flat ground. The US EPA cycle is somewhat more demanding, which is why EPA numbers tend to be closer to reality than WLTP, though still optimistic in cold climates.

In practice, most drivers see 70 to 85 percent of the WLTP figure under normal mixed conditions. In winter that can fall to 60 percent or below. A car rated at 500 km WLTP might deliver 380 km on a mild autumn day and 280 km on a cold motorway run in January.

The key difference is that the official test does not simulate cold batteries, sustained high speed, heavy loading, or consistent use of the heater at full output. Real driving involves all of those at once.

The main factors that reduce real-world range

Cold weather and cabin heating. Battery chemistry slows at low temperatures, reducing both capacity and the rate at which energy can be discharged efficiently. On top of that, a resistance heater running at 3 to 5 kW to warm the cabin draws power continuously. Together, cold and heating can reduce range by 25 to 40 percent compared to a mild day. Heat pumps, now fitted to most newer EVs, recover much of that loss by moving heat rather than generating it directly.

Speed and aerodynamic drag. Aerodynamic drag rises with the square of speed. Driving at 130 km/h instead of 100 km/h increases drag by roughly 69 percent. This is the single largest variable most drivers can control. Dropping from motorway speed to 90 km/h can add 60 to 80 km to a trip on a large-pack car.

Terrain and payload. Climbing adds direct energy cost. A sustained climb of 500 m of altitude with a 2,000 kg car costs around 2.7 kWh just for the elevation gain, not counting road losses. Passengers and luggage add mass, which increases rolling resistance and makes acceleration more expensive. Regenerative braking can recover a portion of energy on descents, but not all of it.

Battery age. Lithium-ion cells lose a small percentage of capacity each year, typically 1 to 2 percent annually under normal use. A five-year-old car might have 88 to 93 percent of its original capacity remaining, which trims range proportionally. The decline is gradual and most drivers notice it only over multiple years.

Regenerative braking. Regen converts kinetic energy back to electricity during deceleration. On urban routes with frequent stops it can recover 15 to 25 percent of the energy that would otherwise be lost as heat in conventional brakes. On long motorway runs with few slowdowns the benefit is small because there is little deceleration to capture.

How to estimate your own range

The most accurate source for your real consumption is the trip computer in your own car. Most EVs display a rolling average in Wh/km (or Wh/mile in markets using imperial). To estimate remaining range at any point, divide the remaining usable kWh by your current average. If the car shows 28 kWh remaining and your rolling average is 175 Wh/km, you have roughly 28,000 / 175 = 160 km available under those conditions.

For planning ahead, use separate figures for each leg of a journey. A flat motorway section at 120 km/h might consume 220 Wh/km while a slower urban stretch runs at 140 Wh/km. Blending those appropriately gives a better estimate than using one flat average for the whole trip.

The EV range and charging cost calculator lets you plug in your own capacity, consumption rate and electricity price to get a quick answer without manual arithmetic.

Practical tips to get more range

Reduce motorway speed where the route allows. Dropping from 120 to 100 km/h is consistently the highest-return adjustment available.

Pre-condition the cabin while the car is still plugged in, using grid electricity to reach temperature before departure. This removes most of the heating load from the driving range budget.

Keep tyres at the upper end of the manufacturer's recommended pressure range. Under-inflated tyres increase rolling resistance noticeably and cut efficiency by 1 to 3 percent per bar of deficit.

Use eco or range mode on long trips. These modes typically cap top speed, reduce heating output and increase regen, all of which shift the efficiency curve favourably.

On longer journeys, charge to 80 percent rather than 100 percent, and plan charging stops at 15 to 20 percent remaining. Fast chargers slow their output significantly above 80 percent, so stopping earlier and more often is usually faster than waiting for a full charge.