If your actuall "ALL costs included" price per KWH of electric is in the 8.3 cents (US equivilent) range, that's not going to work well IF at all for a major mining facility.
3c / KWH on the other hand IS a good price range to run a major facility.
Make sure you are looking at ALL of the costs though, not just the base rate charge. In many cases the "added charges" and surcharges total up to MORE than the base rate does.
2 MW is not "substation" power draw range, but it DOES take some substantial investment in infrastructure. Check out the Great Northern Data thread for some information - they're bigger than that, but not in a range that they're completely different on infrastructure requirements.
675 TH by current standards isn't all that big of a farm - it's definitely not SMALL but by the standards of the Major Farms it's definitely on the low end.