yeah lights out is no problem for corals,sometimes they go like a week without light because of storms in the ocean.
i personally had my lights off for 3 days once because i ran into a cyano issue when my tank was 3 months in.
the thing that corals would need the most is flow,i have my swc160 with a DIY battery backup so whenever there is a power outage i just put it inside the main display and it puts out a good amount of flow and aerates the water because micro bubbles come out.
i was once out of power for a day and after being out of power for 3 hours i drove to best buy and bought a plug that goes into the car that has two ground plugs inside of it and just got an extension cord,plugged my vortech in and ran the car for a few hours.