An off-grid home has its own complete, self-contained power generating station. It is independent of utility power lines (the "grid"), and all power needed by the home is produced on-site. Because they are isolated from any grid support, offgrid systems require careful matching of system capacity, energy storage capability, and system loads.
A typical off-grid home will have a solar array, a battery bank, an inverter, and a number of other components needed for system control, monitoring, and safety. Off grid home systems often include additional energy sources for use during extended periods of cloudy weather. These may include renewable sources such as a windmill.
Grid tied homes are connected to the electric utility lines. This allows the home to utilize and/or store solar electricity when the sun is shining and to use utility power when the sun is not out. In the event of a utility power failure, this type of system can automatically switch over to battery power.
While the utility power is out, this house functions as an off-grid home. When the power comes back on, the system automatically switches back to using a combination of solar and grid-power. The homeowner may never even know there has been a power failure.