The simplest and most cost-effective PV design for most sites is the "Grid-Tie" (sometimes referred to as intertied or utility-interactive) system. This system does not provide backup power during a power outage (even if the sun is shining) but for sites with reliable grid power, this is usually the logical system choice. This system is synchronized with the utility supply mains at the distribution box. It uses an inverter which has special provisions to match the grid supply using sensors and reduce the total power consumption from the grid.
Net metering is a billing mechanism that credits solar energy system owners for the electricity they add to the grid. It allows Utility power consumers who generate some or all of their own electricity to use at anytime, instead of when it is generated allowing the consumers to give extra solar power into the grid when their demands for power are met and recover the grid injected energy whenever their generation from the solar system is low. This system enables the consumer to achieve a substantial reduction in the electricity bill (The bill could be as low as zero in some cases).
Net metering allows residential, industrial and commercial customers who generate their own electricity from solar power to feed electricity they do not use back into the grid. Many states have passed net metering laws. Differences between states legislation and implementation mean that the benefits of net metering can vary widely for solar customers in different areas of the country.