Well, recently, 8 days, and my corals all lived, upstairs, just on room light such as it was in 8 days with no power. In the sump, without light, the cheato was a messb.
But that's not optimum.
Suggest you go to a hardware, get a shoplight clip and a 6500 k daylight 100 w bulb, and use that until you get your lights.