Solar Glossary

Alternating current (AC) = the type of electric current that powers all electric appliances in your home.

Array = a set of photovoltaic panels. A home solar electric system might include several arrays on different parts of the roof.

Balance of System (BOS) = all the parts of a solar electric system excluding the solar panels and the inverter. Balance of system usually includes items like racking, wires, conduit, and safety shut-offs. The balance of system might account for 15% of the total cost of a solar electric system.

Base load = the amount of electric power a utility must supply constantly to meet the demand for energy.

Battery = a battery back-up for a solar electric system stores the extra power the solar system makes. A home can use that power when the solar system isn't producing enough energy, at night, or in a power outage.

BIPV panel = a type of solar electric panel that uses silicon as a semiconductor and acts like a part of your roof. They're also known as solar roof shingles. BIPV can be done on new or existing roofs.

Cell = the smallest part of a solar panel that converts light into solar electricity.

Direct Current (DC) = a type of low voltage electrical current. DC electricity is produced by solar cells and must be converted into AC before it's usable in a house.

Gigawatt = one billion watts.

Grid = a system of high tension cables in a region that distributes electricity to homes, businesses, and other buildings.

Grid tied/Grid connected = a solar system that is connected to the power grid and uses the grid as a backup source of power.

Ground mount = a solar electrical system that is mounted on the ground instead of on a roof.

Interconnection = the process of hooking up a solar electrical system to the power grid.

Inverter = the electrical device that converts direct current (DC) electricity into alternating Interconnection the process of hooking up a solar electrical system to the power grid.

Kilowatt = One thousand watts.

Kilowatt-hour (kWh) = 1,000 thousand watts acting over a period of one hour. A kWh is the unit of energy.

Megawatt = one million watts.

Monocrystalline panel = a solar panel that's made from a large, single silicon crystal and has a patchwork pattern. Monocrystalline panels are more expensive and more efficient than multi- or poly- crystalline panels.

Multicrystalline panel = (also polycrystalline) a solar panel that's made from small silicon crystals oriented in lots of different directions. Multicrystalline panels are less expensive and less efficient than monocrystalline panels.

Module = a solar panel, or a group of solar cells.


Net meter = an electricity meter that spins both forward and backwards. It can track how much electricity your solar system puts into the power grid and how much electricity your home pulls out of the grid.

Panel or Solar Panel = a group of solar cells; a module.

Photon = a "packet" of light energy.

Photovoltaic = the process of converting light into electricity.

Power purchase agreement (PPA) = a contract between a power produce and a power consumer, which states that the consumer will purchase a certain amount of power from the producer.

Semiconductor = a material that has a limited ability to conduct electric current. Semiconductors used in different types of solar panels include copper indium diselenide, cadmium telluride gallium arsenide, and silicon.

Silicon = a dark gray, semi-metallic, chemical element. Silicon is the material most commonly used semiconductor used in solar cells and computer chips.

Solar constant = the average amount of solar radiation that reaches the earth's upper atmosphere, equal to 1353 watts per square meter. 

Solar energy, solar power or solar electricity = power that is generated by the sun.

Solar noon = the time of day when the sun reaches its highest point in the sky. This time divides the daylight hours for that day exactly in half. Solar noon may be quite a bit different from 'clock' noon.

Stand alone/off grid = a solar electric system that is not connected to a power grid and which may or may not have a battery.

Thin film panel = a solar panel that is thin and flexible. The term refers to both amorphous photovoltaic solar panels, which use silicon as their semiconductor, and panels that use other semiconductors like cadmium telluride and copper indium gallium diselenide.

Tilt = the angle a solar panel makes with the horizon. The ideal tilt for a location will mean that the panels absorb as much sunlight as possible.

Tracking panels = solar panels that can change the direction they face to follow the sun's movements.

Watt = a unit of power equal to amps times volts