These systems can also feed power back into the grid during times of low consumption and high production (This is only allowed in certain areas in South Africa.)
If your primary objective is to reduce your utility bill, get the best return on investment and you are not concerned about the grid stability and load shedding, then a grid tied system is the appropriate solution for you. Backup power is available through the utility (Eskom) if the solar system does not produce enough or any power.
These are simplest systems and the most cost effective systems to install. The pay back period by offsetting the utility bill savings is generally 5-7 yrs.
Depending on the capacity of your installation and whether you are in an area that allows feed-in credits for the excess power generated, you can expect savings of between 30 to 50 percent.