People usually arrive with one of two frustrations. Either the power keeps going off, or the bill keeps going up. Those lead to different systems, and conflating them is how buyers end up spending more than they needed to or less than they hoped.
If the problem is continuity
A battery backup system keeps selected circuits running when the grid fails. It charges from the grid, so it does not generate anything and it will not reduce your bill. In fact it will raise it very slightly, because charging is not perfectly efficient.
What it buys is that the lights, the internet, the fridge and the alarm carry on. For many households that is the entire requirement and there is nothing wrong with stopping there.
If the problem is cost
Solar generation is what reduces a bill. If your property uses most of its power during daylight, a grid-tied array is the lowest cost way to cut import, and it needs no battery at all.
The catch is that a grid-tied array without storage shuts down during an outage. It solves the bill and does nothing for continuity.
If the problem is both
A hybrid system generates, stores and rides through outages. It costs more than either of the other two because it is doing both jobs.
It is the right answer for most West Coast homes we assess, but it is worth arriving at deliberately rather than by default.
Start with backup, add generation later
A common and sensible path is to install a backup system now and add panels in a later phase. This only works if the first phase is specified for it, which means the inverter, the cabling and the distribution need headroom from the start.
Ask that question before you sign, not afterwards. It is a small decision at phase one and an expensive one at phase two.