There are 3 basic types of systems – grid connected, grid connected with battery backup and off grid. Grid connected is the most common and the most efficient for a majority of the applications.
Net metering is the billing process in which a system is connected to the grid. The power produced by the system is used when there is a need on the site’s loads. If the system is producing more than site’s needs the energy is then put back out onto the grid and used by another consumer. The producer is credited on a 1 for 1 basis up to net-zero no revenue is produced. During slow times of production the consumer simply pulls power from the utility at normal rates.