Francis Knows: Net Metering
Net metering is a billing mechanism implemented by your local utility that credits solar energy system owners for the electricity they add back to the electric grid. Typically, homeowners work during the day when the system is producing the most energy, and are home consuming the most energy in the evening, when the sun is low. Net metering allows for energy exported to the grid to be valued at the same rate as energy imported from the grid.
Monthly net metering credits you for the month in which a solar kilowatt-hour was produced. If the net energy usage for that month is below zero, the remaining energy is not credited back to the customer. On such plans, it is a best practice to size the system accordingly and not end any months with net excess production.
Yearly net metering will roll-over any excess energy produced in a month and credit it to the next, allowing a customer to cover their full yearly energy usage and be credited fully for all kilowatt-hours produced. Some utilities will even reimburse you for excess production yearly!