Until quite recently, I commuted all year round for 20-odd yrs on my Africa Twin, albeit here in southern UK it rarely gets much below freezing. But even at freezing, or a few degrees above, it's still cold on the hands, and having cold hands is miserable. So I put Oxford Hot Grips on the 'bars.... they certainly made a difference, but really only warmed-up my palms (unless I held onto the grips using a strange, claw-like posture). The bike also had OEM brush guards which I guess deflected some of the cold air away from my hands. Then came the revelation.... heated gloves. So much better than heated grips, they keep hands beautifully warm. They're made by Gerbing and can be wired to the bike's battery or used with small independent batteries which last up to around 3 hours before a re-charge is needed. Otherwise, I stay warm enough with lined Goretex gear.
Now I work at home I sort of miss the year-round bike commute.