Net metering allows electricity consumers who generate their own electricity from renewable energies to feed electricity they do not use back into the grid. Many states have passed net metering laws.
Net metering is a billing mechanism that credits renewable energy system owners for the electricity they feed into the grid. For example, if a residential customer has a PV system on the home's rooftop, it may generate more electricity than he uses during daylight hours. If the home is net-metered, the electricity meter will run backwards to provide a credit against what electricity is consumed at night or other periods where the home's electricity use exceeds the system's output. Customers are only billed for their "net" energy use. On average, only 20-40% of a solar energy system’s output ever goes into the grid. Exported solar electricity serves nearby customers’ loads.