1. Typical Accuracy under Steady Conditions
- ≈ 5–10% error: Once your EV has some “learning” data for your driving style and the current route/temperature, its predicted range is usually within ±5–10%. An academic study on real‐world trips (average range ~226.6 miles) found a root mean square error of about 19.5 miles (~8.6%).
- Trip-computer precision: Many drivers report that EV trip computers are highly accurate, with each 10% drop in the SoC gauge reliably corresponding to the same distance if driving conditions remain constant.
2. When Errors Grow (±20–30%)
- Sudden condition changes: Jumping from city streets to a 70–75 mph interstate cruise, adding heavy HVAC loads, or climbing steep hills can spike consumption—and the onboard estimate can lag by 20–30% until its rolling average catches up.
- Extreme temperatures: Very cold or very hot weather alters battery chemistry and HVAC draws, so unless you’ve driven in that exact temperature band recently, initial estimates can be off by 10–20%.
3. Why It Can Be So Good—and Sometimes So Off
- Adaptive algorithms: Continuously update forecasts based on recent kWh/mi, navigation data (route length, elevation), ambient temperature, and predicted HVAC use.
- Learning curve: New cars start without a personalized profile—estimates may be optimistic or pessimistic, then improve over the first few hundred miles as the model refines.
- Test-cycle bias: Official EPA ranges assume standardized speeds, gentle acceleration, and moderate temperatures. Real-world driving often deviates, creating the biggest gaps.
4. Tips to Get the Most Reliable Prediction
- Maintain a consistent driving style and speed to stabilize the rolling average.
- Use built-in navigation: entering a destination lets the car factor in elevation changes and expected HVAC use.
- Precondition the cabin while plugged in so the estimate doesn’t reserve energy for thermal comfort.
- Keep software up to date: automakers refine their range-prediction algorithms via over-the-air updates.
In extreme cold with heating, range can fall by up to 53%, and in hot weather with A/C by about 21%, so plan your trips and charging strategy accordingly.