Are we assuming that the figures quoted are for a 100% charge. They will be even lower than when you have to change only to 80%
Obviously if you’re charging to 80% you’re getting 4/5 if the range. However, if you put half a tank of petrol you’d not be expecting it to go as far.
EV database gives you tested distances although some criteria are a little extreme for UK conditions.
Whilst the concept of simply taking 20/30% off the WLTP range is simple to operate and can be programmed into a website, maybe linking to EV Database would have been a better result. For example, the Kona will fly past 80% of its given range unless you drive particularly badly. The Mokka (according to multiple experiences) says 210 miles and delivers up to 100 miles less in winter. A set 30% loss in winter would still be optimistic for the Mokka and a little pessimistic for the Kona.
I'm Autistic, if I say something you find offensive, please let me know, I can guarantee it was unintentional.
I'll try to give my honest opinion but am always open to learning.
Mark