Net metering is a policy that allows homeowners to receive the full value of the electricity that their solar energy system produces. The term net metering refers to the method of accounting for a photovoltaic (PV) system's electricity production, for example. Homeowners with PV systems can thus offset their electric bill with any excess electricity they produce. As the homeowner's PV system produces electricity, the kilowatts are used first to meet any electric requirements (e.g., appliances, lights) in the home. If more electricity is produced from the PV system than the home needs, the extra kilowatts are fed into the utility grid.
Under federal law, utilities must allow independent power producers to be interconnected with the utility grid, and utilities must purchase any excess electricity they generate. Many states have gone beyond the minimum requirements of the federal law by allowing net metering for customers with PV systems. With net metering, the customer's electric meter will run backward when the solar electric system produces more power than is needed to operate the home or business at that time. An approved, utility-grade inverter converts the dc power from the PV modules into ac power that exactly matches the voltage and frequency of the electricity flowing in the utility line; the system must also meet the utility's safety and power-quality requirements. The excess electricity is then fed into the utility grid and sold to the utility at the retail rate.
Neat. You can sell power back to the power companies.