AC Power (Alternating Current)
An electrical current whose magnitude and direction varies continuously and sinusoidally. AC is the form in which electricity is delivered to businesses and residences. It can be thought of as "standard" electrical power.
A unit of measure that indicates how much electricity, or electrical current, is flowing through your wires.
DC Power (Direct Current)
An electrical current whose magnitude and direction stay constant. The photovoltaic cells on solar panels capture energy from sunlight in the form of DC. In order to power your home or business, this current must be converted to AC by an inverter.
The flow of charged electrons through a circuit. Depending upon its behavior, an electrical current can be alternating or direct (AC or DC).
An electrical distribution board that houses electrical circuit breakers. It is the main point at which electricity is distributed throughout a building. It is otherwise known as a breaker box or electrical cabinet.
Fuels that are derived from natural resources, usually in the form of coal, oil, or natural gas. There is a limited supply of these resources, and they are only located in certain parts of the world, making them subject to political and international maneuvering, and causing energy prices to be unstable.
Gaseous components in the atmosphere that contribute to a gradual warming of the planet. The most prevalent of these gases is carbon dioxide, which is released in large quantities when fossil fuels are burned. Nothing is burned to convert sunlight into power. Since solar energy does not have any gaseous by-products, it is considered "clean."
Grid Connected System
A solar system connected in parallel with the electric utility grid. SolarCity solar systems are grid-connected solar systems.
Ground Mounted Systems
A solar system that is not attached directly to a building, but is supported by a structure that is built low to the ground. Ground mounts are ideal for sites with limited roof space and a lot of open land.
The link between your utility company and your building that enables power to move seamlessly in either direction.
A device that converts DC power captured by the photovoltaic cells on solar panels into AC power that can be used to power your home or business. This device is an integral part of a solar system. Large solar systems may have more than one inverter.
A measurement of power. A kilowatt is one thousand watts. The size of a solar system is often measured in kW. A typical size solar system for a home is 5 kW; for a medium sized business is 100 kW.
KWh (Kilowatt Hour)
A measurement of energy consumption. One kilowatt hour is defined as the amount of energy consumed by a 1000-Watt appliance running continuously for 1 hour. This is the measurement your utility company uses to calculate your electric bill.
An agreement between a solar system owner and the local electric utility that allows the system owner to buy and sell energy in the form of electric credits. When the solar system produces excess energy, it is sold back to the electric utility at peak prices, literally causing the electric meter to spin backwards. When the system is not producing energy, the system owner can use the credits to buy back energy at off-peak prices.
On/Off Grid System
A solar energy system that is interconnected with the utility grid is said to be an on-grid or grid-tied system, while a system with battery storage is not interconnected and is described as an off-grid system.
Photovoltaic (PV) System
PV systems convert sunlight and ultra violet light directly into electricity. Solar thermal systems use a different technology that uses sunlight to heat water or air, often used to heat swimming pools. SolarCity primarily designs and sells PV solar systems.
PowerGuide™ Energy Monitoring
A service that constantly measures and displays how electricity is used throughout your building. Understanding your energy usage patterns can help you save money by informing smarter choices on how and when you use electricity. For instance, shifting energy intensive activities to off-peak hours when utility prices are lower.
Power Purchase Agreement (PPA)
A Power Purchase Agreement (PPA) is an agreement between a homeowner/building owner and SolarCity, where SolarCity covers the full cost of installing and maintaining a solar system. In return, the host customer agrees to buy the power produced by the system. This allows building owners to pay as they go, rather than in one large upfront payment.
Roof Mounted System
A solar system in which solar panels are mounted directly on the roof of a building or adjacent structure. The majority of solar systems are mounted on a roof.
A group of solar panels collectively makes up a solar array.
Electromagnetic energy transmitted from the sun. In order to power buildings, this energy must be captured and converted to AC electrical power.
SolarLease is the brand name for SolarCity's residential solar leasing option. Homeowners pay a fixed monthly payment for their solar system, and can get started with no money down. SolarLease can make it possible to switch to clean, solar power for less money than homeowners currently pay for electricity. SolarLease is not available in all areas.
A group of solar cells arranged into a panel that can be installed onto a flat surface. Also can be called solar modules. The panel captures sunlight and converts it into DC power.
A solar energy system that is not connected to the utility grid. Also called an off-grid system. To provide continuous power, these systems must be connected to storage units that can store excess power produced during daylight hours for use at night.
A service that continually tracks and displays the production of your solar system so you and SolarCity can make sure your system is performing as expected.
The angle at which a solar array is tilted towards the sun. Depending on the geographic location of a building, a solar array might be installed flat or tilted.
Time-of-Use (TOU) Rates
A utility billing system in which the price of electricity depends upon the hour of day at which it is used. Rates are higher during the afternoon when electric demand is at its peak. Rates are lower during the night when electric demand is off peak.
The infrastructure of power lines, transformers and substations that delivers electric power to homes and businesses. The utility grid is owned and managed by electric utility companies.
A device that measures the flow of electricity between a site that uses electricity and the electric utility company. When your solar system produces excess power, your meter literally spins backward.
The amount of force required to drive a steady current. Electrical systems of most homes use 120 volts.
The Watt is the standard unit of measure for power, either by capacity or demand. For example, light bulbs are classified by wattage.
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