I'm an introvert, yes.
The rate of exhaustion for me depends on who the person/people is/are, how big the group is, how long I went without human interaction (aside from family) before I hang out with the person/people, where we are hanging out.
Going to the movies with 10 people would not exhaust me. Going to dinner with 10 people would.
Basically, the more effort I have to put into the interaction, the quicker I become exhausted.