PV Connected to the Utility Grid
The request to "fill 'er up" takes on a whole new meaning at this solar electric home in Palo Alto, California. The photovoltaic (PV) system on the roof, which generates ample electricity for household uses, also recharges the electric vehicle in the driveway. Atlantis Energy Sunslates (PV roof tiles) and AstroPower PV modules make up the 5-kilowatt system, which has a battery backup and is also tied into the local utility. The City of Palo Alto Utilities Department helped fund this demonstration project.
Using grid-connected PV power can have economic as well as environmental advantages. Where utility power is available, consumers can use a grid-connected PV system to supply some of the power they need and use utility-generated power at night and on very cloudy days. When the PV system supplies power to the grid as well as to a specific building or piece of equipment, the utility becomes a kind of storage device or battery for PV-generated power.
Several homeowners, considered pioneers in the use of renewable energy, have sizable PV systems connected to the utility grid. They like that the system reduces the amount of electricity they purchase from the utility each month. They also like the fact that PV consumes no fuel and generates no pollution.
The owner of a grid-connected PV system can often sell as well as buy electricity each month! This is because electricity generated by the PV system can be used on site or fed through a meter into the utility grid. When a home or business requires more electricity than the PV array is generating (for example, in the evening), the need is automatically met by utility power. When that home or business requires less electricity than the PV array is generating, the excess can often be fed (or sold) back to the utility through net metering, which is becoming more and more common throughout the nation. At the end of the month, a credit for electricity sold is deducted from charges for electricity purchased. See also the case study of an energy-efficient home for an example of this.