If the AC system is running on DC internally (e.g. DC fans instead of AC) then you have DC --> AC --> DC conversion and should probably figure about 10-15% loss

If the AC system is running on DC internally (e.g. DC fans instead of AC) then you have DC --> AC --> DC conversion and should probably figure about 10-15% loss at each of those. For convenience, call it a 25% loss of efficiency overall so not insignificant. Edit: AC has advantages in transmission over distances, but if you're looking at both solar panels and AC units on the same roof distance is probably not a major factor.