I got Leviton load centers for the breakers in my house, which are backed up by our home battery; one panel has been in for over a year, and the installation on the other just finished today. My plan all along has been to do exactly what you’re suggesting – if a grid power loss occurs, switch off specific breakers so we are only pulling from the battery for the most important things (refrigerator, internet modem, basic lighting).
Since most of my most impactful loads (heat pumps, water heater, exterior lighting) are on the panel that just got installed today, I hadn’t set up my “in case of power failure” automation yet. But as a first step, I have long had an automation in HA set up to detect when the grid is cut and battery backup starts; so far, I just get a notification from HA, but my next project will be to also instruct the Leviton integration to switch off breakers. The option is pretty straightforward, see screenshot (this would shut off air conditioning, as an example).
