AC Power (Alternating Current)
An electrical current whose magnitude and direction varies continuously and sinusoidal. AC is the form in which electricity is delivered to businesses and residences. AC is often thought of as the standard for electrical power.

A unit of measure that indicates how much electricity, or electrical current, is flowing through wires.

DC Power (Direct Current)
An electrical current whose magnitude and direction stay constant, the opposite of AC. The photovoltaic cells on solar panels capture energy from sunlight in the form of DC. In order to provide power, this current must be converted to AC by an inverter.

Electrical Current
The flow of charged electrons through a circuit. Depending upon its behavior, an electrical current can be AC or DC

Electric Panel
An electrical distribution board that contains electrical circuit breakers. Also known as a breaker box or electrical cabinet, it is the main point of electricity distribution in a building.

Fossil Fuel
Fuels that are derived from natural resources, usually in the form of coal, oil, or natural gas.

Greenhouse Gases
Gaseous components in the atmosphere that contribute to a gradual warming of the planet, known as global warming. The most prevalent of these gases is carbon dioxide, which is released in large quantities when fossil fuels are burned.

Grid Connected System
A solar system that is connected in parallel with the electric utility grid.

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. Best suited for open land with or a building with limited roof space.

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. Larger solar systems may have more than one inverter.

kW (Kilowatt)
A measurement of power. A kilowatt is one thousand watts. The size of a solar panel system is often measured in 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 used by your utility company to calculate your electric bill.

Net Metering
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, causing the electric meter to spin backwards.

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.

Power Purchase Agreement (PPA)
A Power Purchase Agreement (PPA) is an agreement between a homeowner/building owner and a solar panel provider, where the provider 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.

Roof Mounted System
A solar system in which solar panels are mounted directly on the roof of a building.

Solar Array
A group of solar panels collectively make up a solar array.

Solar Energy
Electromagnetic energy transmitted from the sun.

Solar Panel
A group of solar cells arranged into a panel that can be installed onto a flat surface.

Stand-Alone System
A solar energy system that is not connected to the utility grid. Also called an off-grid system.

Tilt Angle
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 billing system in which the price of electricity depends upon the hour of day at which it is used. Rates are generally higher during the afternoon when electric demand is at its peak.

Utility Grid
The infrastructure of power lines, transformers and substations that delivers electric power to homes and businesses.

Utility Meter
A device that measures the flow of electricity between a site that uses electricity and the electric utility company.

Volt (V)
The amount of force required to drive a steady current. Most homes use 120 volts.

Watt (W)
The Watt is the standard unit of measure for power, either by capacity or demand.

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