Before purchasing any battery storage it is critical that you understand what you want to do with the battery. If you only want to shift some energy generated from your solar panels during the day to be used at night and don’t mind if you don’t have power when the grid goes down it isn’t as critical that your battery needs to be able to provide all the power you need.
However, if you want to be energy independent and want to have power in times of power outages (as most people do that purchase batteries) then you need a battery that is capable of running your house for a period of time. You need to consider your appliances and what you consider essential and determine what power will be drawn down by all of them. As can be seen in the above image you may need multiples of some battery technologies to accomplish this which may greatly increase the cost of an installation.