Proper Sizing of the required battery bank has to be done to prevent unwanted wastage. 

The number of solar panels is dictated by the size of the battery bank which further depends

on the requirement.

You don't what a situation where the batteries are undercharged as this destroys them.

Consider the right inverter size for your load as over-sizing results to overall system 

inefficiency if the load is way lower than the inverter output power.

Lastly solar power is expensive both installing and running as the cost per kwh is higher

as compared to mains power for the same task. Unless there is no mains electricity or 

you what backup go for solar.