It CANNOT be stored.
Solar power can be predicted a little bit better than wind power, but it CANNOT be stored in anything other than very inefficient batteries or pumped units.
An exception: solar HEAT units can store the sun's power from one afternoon into the next night, and release that heat later back into the same house, but that is only heat energy. The released heat cannot heat your neighbor's house, your car, nor light your basement that night.
Typically, you get no more than 6 hours of solar power each day. The rest of the time, you MUST have a reliable grid connection. Or a huge and lethal battery bank.
Some end-use applications can provide storage of excess energy. The classic example is chilled-water storage for building or campus A/C, in which a large water tank is chilled at night when energy is less expensive and that water is used for the A/C in the day. Such systems can be brought online relatively quickly, any time of day, to absorb grid excess.
But, to be blunt, relatively little electric power goes into such applications.
There’s the real use of solar, heating water and building space. Even on cloudy days solar heat is available and a well insulated building could probably use it as a sole means of heating most of the time.
Since installing solar heat isn’t complicated or difficult to install during construction I would think the payback time wouldn’t be too long.
if I may
Solar power can be stored - in the form of liquid salts or sodium. This is only in the big boy plant which use solar heat to run steam turbines. THe stored heat is used to run the steam turbine at night.
All have some kind of backup in the form of fuel oil or natural gas.
FOr home PV system, large battery banks are used. I have remote property that is all solar - and battery......