When looking at solar energy there are three different ways in which the systems can be connected to provide power for your appliances. These being Grid Feed, Grid Switched and Off Grid.
In Australia there is a strong push towards Grid Feed solar systems (where the national power grid is available that is). In a Grid Feed system the panels provide power into the national power grid. If you produce more power than you consume, then your electricity tariff meter runs in reverse and you get a credit towards your power bill.
In a Grid Feed system the solar grid feed inverter synchronises to and runs in parallel with the grid, feeding excess production into the grid and then drawing from it as required depending on the availability of solar energy and the electrical load presented by appliances at any given time.
Grid feed systems do not provide any electrical isolation or protection from mains borne disturbances and outages as they are in “parallel” with the mains supply. Neither can they guarantee supply, because they have no battery back up and in my opinion if you are spending thousands of dollars on an advanced power system it should be fail-safe and guarantee stable supply.
Off grid systems are at the opposite end of design possibilities. Here you use batteries to store the electricity being supplied by the solar panels. Power is then drawn from the batteries as needed to supply your appliances.
The only disadvantage of an off grid system is that excess power generated once your batteries are charged is often unused and if the battery voltage as a result of power consumption falls too low, then you will either have to use a backup generator or wait for the sun to come back and charge your batteries once again.
A grid-switched system is the best solution for those with access to the national power grid. In this system you still use batteries to store your power, but should the voltage become too low then the system automatically switches your home over to use the national power grid.