This is the most common form of solar system installed in America. The inverter converts the electricity generated by the solar system – which is direct current (DC) – into AC electricity so that the power generated is compatible with the grid. Most houses with grid-connect solar systems use solar power first before sourcing electricity
from the grid. When the panels are not producing electricity at night, electricity is supplied from
the electricity grid.
Grid-connect PV systems with battery back-up (sometimes referred to as uninterrupted power supply or hybrid solar PV systems) are becoming increasingly popular. With solar customers in many states now receiving a low price for electricity sold back to the grid, battery back-up systems can be a viable alternative as they use the electricity stored during the day to run your house at night. They also have the advantage of being able to supply power during power outages.
Stand-alone systems are not connected to the electricity grid and typically are installed in remote areas where there is limited connection to the grid, or areas of low electricity demand. Unlike their grid-connected counterparts, these systems must have batteries or backup generation to provide supply at night. In many cases they will also include a diesel or petrol generator to supplement energy supply.