The net metering system is also used in a grid-connected house, but instead of storing power in batteries, it is sold to the utility company.
The net metering system employs a special type of inverter, which inverts DC power from the PV array into low distortion full sine wave AC power, acceptable for purchase by the local utility power company. Batteries are not required for storage. The power is delivered through a kilowatt-hour (kWh) meter to the utility grid as it is produced by the PV modules. A second kWh meter is sometimes used to measure the power consumed.
The user of this system will notice no difference from any utility run system, except lower utility bills or possibly payments from the power company for the excess electricity that is generated.
Until recently, the net metering system requires a PV array of 1000 watts or more (12 or more PV modules) to be cost effective since the smallest intertie inverters were 1000 watts (1 kW). Recently, a new, smaller utility intertie inverter has become available, allowing systems as small as 100 watts to feed power back into the grid. Any electricity fed into the grid must be compatible with the power generated by the utility or problems might arise.
Net metering system require utility power to operate, so a house of this type will have no electricity during a power outage. Adding a battery bank to the PV system would provide power during outages.