Most grid-tied systems do not have batteries, and therefore have no way of storing their electricity. Consequently, if the grid goes down, so does your home power.
Because your system can feed energy onto the grid, safety mechanisms are in place to protect utility lineman while they work hard to restore power. It is critical that no net-metered systems are feeding the grid when the grid is down.
If you are concerned about power-failures, Harvest Solar can design a battery-backup system that will allow you to provide power for critical loads such as well pumps, refrigerators and heat sources.