Probably your worst situation is lots of short trips where the car is parked in the sun, and you have the a/c set to a generally comfortable range. Well, on the REx, in the cold, heating is all via resistance heat, which is a lot less efficient than the cooling or heat pump on the BEV. It takes a lot of energy to cool the interior of the i3 with the large front windscreen. If you live in an area where they allow tinting the front windows, you might consider something like 3M's crystalline tint...even in the lightest tint, it blocks a significant amount of IR and UV light with the 200-layers of coatings on it. Then, running fast and not anticipating stops and using regeneration while actually using the friction brakes often messes up range. Not holding a steady speed, where you're constantly speeding up and slowing down (regen is never 100%) messes things up as does climbing a grade. Recently, I sat in a long line to get a COVID test (luckily, came out negative) and my efficiency for that trip was like 1-mile/kw...pretty dismal, but it was hot out, and was essentially not moving for most of the trip.
So, given the rolling average, some little things can combine to show either really good or really bad efficiency
2014 i3 BEV, 2021 X5 45e
(The i3 will be sold soon, <17K-miles, interested?)