The least expensive way to "store" solar power for
night-time use is to feed it into the nation-wide
power grid during the day.
During the day, such a "grid tied" solar power system
runs the homeowner's power meter backwards as it generates
electricity and helps to power the grid.
At night, the home uses power from the local grid just as
it did before the home had solar panels.
During the day you are selling power, and at night you are
buying power.
You have no batteries to maintain and replace. Instead,
the inverter you use to convert solar direct current into
household alternating current has a special feature.
That feature is the ability to "sync up" to the external
alternating current, and feed power into the grid.
The inverter knows how to shut itself off when the external
power fails. This is a safety feature, so that the workers
repairing the external power are not electrocuted by the
power provided by the solar panels.
Most grid tied solar power systems will not feed power to
the house when the external power fails. This is a drawback
to the current designs, but even if the inverter simply
shut itself off from the outside power, you would still
have no power at night, and there would still be a "glitch"
in the power when the inverter had to sync up with the external
power when it was restored.
If you want to be free of external power problems, you will
want either an "off grid" system that had battery backup,
or purchase smaller uninterruptible power supplies for
critical things such as computers, medical refrigerators,
or other essential equipment. For some, this includes the
television, and home refrigerator, but more often it is
room lighting.