It depends on the size of the AC, age of AC, cooling capacity, the SEER rating, and other factors. But A 5-star air conditioner (1.5 tons) consumes 1.6 units each hour.  Whereas a 3-star air conditioner (1.5 tons) uses 1.7 units each hour. So, a 5-star 1.5 ton AC would use 40% less power than a 3-star 1.5 ton AC.