Road distance – 510 Kilometers (316 miles)
Travel time – 10 to 14 hours (By bus)
Traveling from Delhi is straight and time saving, because from Ambala most buses skip Chandigarh by passing through Kiratpur sahib by-pass.
Click here for CHANDIGARH-KASOL journey details

Ticket fare – Rs 700 to Rs 2000, depending upon AC or non-AC buses.
Boarding points – Paharganj, Majnu ka tila, Vidhan Sabha metro station and Karnal bypass.
Dropping point – Bhuntar (30 KM from kasol)
(If bus is to going to Manikaran, drop on the way at Kasol)
Most buses leave in evening (by 1900 hours) and will stop for dinner and loo break, before reaching bhuntar in early morning. If you don’t have car facility. It is recommended to reach bhuntar at least by 7 pm, because after that local buses don’t provide service. And local cab will ask around Rs 1200 (if in group, try negotiating from Rs 100 per person), whereas buses take around Rs 55.
Volvo and private buses are easy to find, but are little expensive. You can also go for government buses that are not as comfortable as Volvo, but yeah AC is there and one can sleep overnight. (Check HRTC website).
If traveling anywhere from India- South, east or west,one is most likely to go via  Delhi only.