Dear Sire,
Thanks for contacting the world's largest BMW owners forum
The "EV range" is hugely impacted by outside temps, driving environment (highways vs B-roads vs city) and your driving style. Smaller the battery back (plug-in hybrids), more noticeable is the range fluctuation. These all affect much, much more than with petrol engine cars. For example how cold its in the UK now?
1. Colder winter temps = battery is drained faster than during spring / fall. Especially cabin heating will drain battery but also during summer AC will drain up to 2-3 miles of real life range. The best EV range is generally achieved during spring or fall when AC is OFF (use normal HVAC w/o AC), car is in ECO PRO -mode and outside temps are something like 10-15C or 50-60F.
Mine is 2014 model and I can achieve over 30km / 18 miles on pure electric range when driving 60-80kph limited country roads, Eco Pro -mode enabled and using HVAC w/o AC. But like I said, the range is hugely affected for example speeds, your driving style and traffic environment etc. I paid 300 euros for the official BMW "battery back test" and got figure of 98%. 10 year old vehicle with 85k km or 53k miles on the odometer.
2. Keep the car plugged in your home charger and use cabin preheating / precooling option via BMW app. This will significantly impact your EV range. With out it the cabin heating (cold morning starts) really drains the battery pack. If you do not have home charger, then you'll get much less EV range no matter the time of the year, sir.
3. The "estimated range" is calculated by the ECU. It shows less range when battery has been heavily used (cabin heating etc) and it takes into account last few "driving sessions" when showing expected range. Kind of MPG in city vs country roads.
With any BMW in general the Comfort Mode is basically similar to Eco Pro -mode only major difference being that in Eco Pro -mode the car will use HVAC / AC / heating system in more ... how to say it, in more "restrict manner". Also shift points are lower (when driving with petrol engine) and the accelerator pedal is tad more lenient.
If the cabin will not "fog up", just use Eco Pro -mode when daily commuting, especially if you want to extend the EV range or your MPG.