For a long time I was told that our extroversion was determined by where we get our energy from, but in my experience that doesn't seem to reflect how social people are. I have heard stories of people who are social but need time alone to regain energy, and vice versa.
Also, extroverts are supposed to make up 70% of the population. I think about 90% of the people I know get their energy from being alone.
It seems that your energy source and your sociability are two separate groups. In my opinion, we should just redefine extroversion as one's sociability, because one's energy source doesn't seem very useful.