I recommend you look at a separate backup system that charges from your existing AC.
Essentially this would be an appropriately sized battery bank, inverter, and charger that charges the bank from your existing outlets. You're basically building your own beefier UPS, so only things plugged into it would have power if the grid is down.
You could also do a whole house backup, or DC/AC coupled systems but you're looking at significantly more $$. Depends on sizing, but can be done for under a grand with a small standalone, versus more than 10 times that for a whole house backup.
Pros of separate system: cheaper, can be sized down to emergency needs only, legal to self-install if not hard-wired, no need for inverter if DC loads only (e.g. charging mobile devices and DC lighting)
Cons: PV would not charge bank in grid-down situation. Does not protect whole house (main one!), less efficient charging batteries from AC vice a DC coupled or whole house backup system (this only really matters if you're off-grid a lot).
That said, if you have the money, an AC-coupled system is probably the way to go. Note that typically this will give you only some loads on the protected panels. Whole-house backup is ideal, but bring $$.