I think it is 95% accurate. As they get there data from Google Keyword Planner & paired with clickstream data with the help of which gives they are able to provide an accurate estimate of search volumes for almost every keyword.
Not very accurate but much dependable than similar tools like ubber suggest and semrush.I have noticed that ahrefs keyword explorer shows low search volume compare to other keyword tools like keywords planner, semrush or Keywords Everywhere. Which one should I consider more accurate? There is a very big difference among ahrefs and others.
As someone who use ahrefs for 3 years+ i would say 20-30% accurate. And for some specific keywords in my niche it is close to 0.