Using first principle calculations, we investigated the energetic and electronic properties of two stacking faults that have been recently identified experimentally in as-grown 4H-SiC homo epitaxial films. We found that both defects generate two separate split-off bands localized below the bottom of the conduction band. The energy of the deepest intra gap state associated with each defect is in excellent agreement with photoluminescence measurements. Furthermore, we calculated formation energies of 0.3 and 2.4 mJ/m2 for the (4,4) and (3,5) defects, respectively, much smaller than the energy of any other stacking fault; this result justifies their dominance in as-grown epilayers.