This is from the book Dead and Gone:
"He had never sounded less like modern man.
'How old were you?'
He considered. 'I was in my early twenties', he said. 'Perhaps twenty-three'... "
This is a conversation between Eric and Sookie, and I don't know is he also 23 is tv- show. I hope I helped.

In the TV show he's thirty two per the season 1 bluray extras.