Yeah, this. There should be some kind of guide...kinda like the #of panels for your area based on sun....to get the proper average ratio of Battery to Solar for your location.... Maybe there is...I'm kinda new to all this..
I think you really have to work up to it from your daily baseline:
1) I started with enough solar inverter output to feed my highest demand. To this end I stuck a sensor on my panel feed, and started recording.
-- I wanted 240V@100A to meet maximum demand
2) Next you will need to figure out the solar output to meet your average daily demand. A perfect day is ~6hours of 100% sunshine.
-- daily kwh = 6hr * panel watts so daily/6 = total panel. Eg 96KWH/day 96/6 = 16 KW of panels for 6 hours.
-- Buffer the number by ~25% for battery charge/discharge loss, and again by where you live.
3) PV is actually on a curve production time here is as much as 10 hours in the summer, much less at the moment. If you expect to be off grid you will need to be storing the difference between usage and production during that window. Using 8 hours as a median you'll need batteries to handle around 2/3 of your daily production, so with our example 96/3 * 2 = 64. Call it about 64KWH of battery minimum. Generally you will not be using as much energy out of sunshine time in sunny hot places. OTOH if you are in colder environments and you are using electric to heat, it's going to kill you if nights are REALLY cold.
This should give you a starting point. Then add panels and then batteries to create your needed buffers based on your environment and desires. I'd go panels first, as they are the least expensive to buy, and most obnoxious to mount, wire, and connect. Further without the excess power to feed your batteries, more battery is useless.
Note: I picked 96KWH/day. That is for my 1500sqft here in phoenix. However for a more northern climate, with gas heat or a pellet stove or something, probably much lower. If you are in an extreme like Juneau,AK where you are lucky to get an hour of sunlight/day and it rains 9 days out of 10, you would have to seriously over-panel hence the complexity. I don't mind hitting the grid off peak here and there and have the luxury of incredibly stable grid, and an abundance of sunlite, so I'm reaping a huge TOU benefit, in summer, even with only 30KWH of batteries. I'll be adding another stack of 30, then I'll reconfigure and bump up the panels. Keep in mind that every KW you over-panel is now storable, so you get a diminishing return as you get past your total daily needs. ie you just need enough excess pv and battery to keep you thru your worst no-sun intervals, and/or above average days.