This is why if possible, you should schedule your charge closer to when you need the car. That way the residual heat from the charging process isn't lost to entropy and preserves your regen during your drive. I haven't quantified it, but this year, my electric usage is way lower than last year, and some of that might be because I've started to schedule charging to start 3 hours before my morning commute, as opposed to charging immediately when I get home. And anecdotally, with just 1 hour of charging, I have the full regen bar back. 30 min gets a lot of it back. this seems way better than relying on just a battery heater to condition the battery.