Easy, but don't forget battery storage is just a buffer for when the solar or genset is not producing energy.
Install your aircon unit (plus DC-AC inverter / DC-DC converter) in your actual box and run it for 24 hrs at a given thermostat setting off a cheap lead battery bank, measuring the Ah consumed at that bank's native voltage.
Of course only good for the heat load inside / ambient outside temp range at that time and that thermostat setting, but gives you a ballpark Ah per 24 hrs.
So just as an example, a 5000 BTU set for 70°F might use 500Ah at nominal 24V, say that rounds to 12kWh per 24 hrs.
85kWh for a current Tesla Model S pack, call its actual availability 60kWh after buck conversion losses, avoiding the shoulders for longevity.
Gives a buffer of five days' usage.
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Of course you need to find say 70kWh of energy on average every five days to put back into the pack(s).
Which is 16kW of panels in sunny weather
or a Honda EU2200i running about a third of the time.