WLTP range figures are measured in lab conditions at 23°C. UK weather isn't a lab. This tool adjusts the official range for season and driving style so you get a number closer to what you'll actually see on the road.
WLTP (Worldwide Harmonised Light Vehicle Test Procedure) is the official UK and EU test standard, run under controlled lab conditions at 23°C with no wind resistance variation and a defined speed profile. It's more realistic than the older NEDC standard it replaced, but it still doesn't account for British winters, motorway-heavy commutes, or running the heating on a January morning.
In our own testing across multiple UK-market EVs, winter range drops of 20-30% below WLTP are common, with the steepest losses on motorway journeys in sub-5°C conditions. This estimator uses conservative multipliers based on patterns reported across UK EV ownership communities and our own road testing, not manufacturer figures.