Range is an estimate
The range shown when an electric car is fully charged is a prediction of how far the car can go. Two kinds of figures exist:
- A published rating, produced by a standardized test procedure. Different regions use different procedures, so the same car can have different official numbers in different places. These figures are mainly meant for comparing cars under identical conditions.
- The live estimate on the dashboard, which the car updates based on recent driving, battery condition and sometimes temperature or route information.
Neither is a promise. Think of the figure like the mileage estimate on a fuel tank gauge, but more sensitive to how you drive.
What is range, in simple terms
Range depends on two things: how much energy the battery holds (in kilowatt-hours) and how much energy the car uses per mile or kilometer. A hypothetical example, with made-up numbers: a usable battery of 60 kWh and consumption of 0.25 kWh per mile gives 60 / 0.25 = 240 miles. If conditions raise consumption to 0.30 kWh per mile, the same battery gives 60 / 0.30 = 200 miles. That is the whole mechanism: anything that raises consumption cuts range.
What affects consumption
Speed
Air resistance grows quickly as speed rises, so energy use climbs sharply at highway speeds. Many electric cars are most efficient at moderate speeds and in town, where regenerative braking helps recover energy. A drive at lower steady speeds usually yields more distance than one at the top legal limit. This is the reverse of the pattern for some combustion cars, which are often less efficient in stop-start traffic.
Temperature
Cold weather is one of the biggest everyday effects:
- Battery chemistry is less efficient when cold, and the car may limit power or regeneration until it warms up.
- Cabin heating draws energy, and in a combustion car this heat is a free by-product of the engine, whereas an electric car must supply it from the battery. Some cars use an efficient heat pump, which varies by model.
- Cold, dense air and wet roads increase resistance.
Hot weather also matters, mainly through air conditioning and battery cooling, but usually less dramatically than cold. The winter driving and hot weather articles cover the broader precautions for those seasons. Part of the loss in winter is temporary and returns when it warms up, which is different from lasting battery degradation.
Load and towing
A heavier car needs more energy to accelerate and climb. Extra passengers and cargo add some consumption. Towing a trailer can reduce range by a large margin, because of both the weight and the added air resistance, and not every electric car is rated for towing. Check the manual.
Aerodynamic drag
Roof boxes, bike racks and open windows at speed increase drag. Taking off a roof rack that you are not using is an easy saving.
Terrain
Climbing uses energy, and descending can return part of it via regeneration, though not all. A route with long climbs usually costs more than a flat one, and a route that ends higher than it begins will take more energy overall.
Driving style
Hard acceleration and late braking waste energy. Smooth, anticipatory driving and good use of the car’s regeneration usually help. The ideas in the article on smooth driving apply well to electric cars.
Tires and wheels
Underinflated tires have higher rolling resistance. Check tire pressure regularly, especially when the temperature changes, and use the pressures the manufacturer recommends. Wider or aggressively treaded tires and some wheel designs can raise consumption; the tire basics article explains how tires vary.
Accessories and auxiliary loads
Heated seats, defrosters, high-powered audio and charging devices use a little energy. Individually they are small, but heating the cabin is generally the biggest.
Battery condition and charge level
An older battery holds somewhat less, as described in the article on how EV batteries age. Also, if you set a daily charge limit below 100 percent, your range per charge is correspondingly lower, by design.
Everyday ways to get more from a charge
- Precondition the cabin while the car is plugged in, so the battery is not used for the initial warm-up or cool-down.
- Keep tires at the recommended pressure.
- Moderate your highway speed where it is safe and legal to do so.
- Remove unused roof racks and heavy items from the trunk.
- Use seat heaters and sensible climate settings instead of heating the whole cabin to high temperatures.
- Plan routes that avoid long, unnecessary detours.
None of these is essential. Together they can make a noticeable difference, but results vary by car.
Using range sensibly
For daily use, most people find that the real range far exceeds their routine distance, so it matters little. For long trips, plan with a margin and use conservative numbers, as described in the article on taking an electric car on a long trip. If the range figure drops suddenly without an obvious cause such as cold weather, or a warning light shows, have the car checked by a qualified technician.
Treat the number on the screen as a guide that updates with conditions, and you will rarely be caught out.