Solar Glossary

The world of solar can feel complex and intimidating at the start, but our solar glossary is here to help. Here’s a handy reference to help you speak the language we use every day; you’ll soon find it’s not as complicated as it can sound! Here are some of the most commonly used terms in the world of solar energy.


AC (Alternating Current)

An oscillating current flow generated by a solar inverter or supplied by the utility grid. This is the current powering your house.

AC Disconnect

An electrical switch that can be operated to isolate the solar electric system from the utility grid, stopping the flow of electricity in either direction.


Alternative Energy Credit, the name given to SRECs in Pennsylvania.

Annual Rate of Return

Annual ratio of money gained or lost relative to the starting investment amount.

Array (Solar Array)

A group of connected photovoltaic solar panels.

Balance of System

All of the components of a solar PV system besides the panels and inverters, which can include racking, attachments, cables, conduit, support structures and other costs such as system design, site preparation, installation, indirect storage, etc.

Ballasted System

A racking system in which your installation is held to the roof with weight and no penetrations are made on the roof’s surface.

Battery Back-Up System

A battery bank sized for power outages or off-grid purposes that may or may not be set up in conjunction with a solar electric system. With solar, batteries are charged during the day to store excess energy even while your solar array powers most or all of a home’s needs. After the sun sets, the battery bank takes over and meets the home’s demand.

Cash Flow Positive

The phrase used to specify the moment your system has paid for itself and true net savings begin relative to the amount you would normally pay your utility company for its power supply.


The building block of a solar photovoltaic panel, a small square made of a layer of silicon and small wires. Each panel may be made up by as many as 72 solar cells.


A type of pipe used to route electrical wiring between devices, such as wiring coming from roof-top solar panels to the electrical meter.

DC (Direct Current)

A steady, non-oscillating current flow generated by solar panels and sent to the inverter


In solar, the amount of captured sunlight able to be converted to electrical current in optimal conditions. Standard efficiency is generally around 14%, High efficiency is around 22%. These percentages mean that 14% to 22% of sunlight is captured and converted to electricity.

Grid / Grid-Connected System (Grid-Interactive) /
Off-the-Grid (Stand-alone)

The Grid is the power network made and managed by the utility company and connected through its power lines.
A Grid-Connected or Grid-Interactive System is a solar installation connected to that network, with the ability to supply energy to the house/business as well as feed excess energy back to the power grid.
An off-the-grid or stand-alone system is not connected to that network and, often with the use power-storage systems like batteries, powers the site independently.


A solar array attached to a structure that is built and installed in the ground, as opposed to being attached to a roof. Groundmounts allow for optimal tilt and orientation for maximum sun exposure.


The device that changes DC electricity from the modules into AC electricity that can be used in your home or sent to the grid.


An agreement established with the utility company for all grid-connected systems, sending power produced from solar PV system to the energy network, tracked by the utility meter.

kWh (Kilowatt Hour)

A measure of the amount of energy supplied over a given time period. For example, one kilowatt hour is the amount of energy produced by a 1 kW system supplying power for 1 hour. This is the most common billing unit used by electric utility companies.

Kilowatt / Watt

A measure of electrical power being generated at any given instant.1,000 Watts (W) is one Kilowatt (kW). Systems are referred to by the amount of power they can produce, such as a 10 kW system.


A device that converts direct current (DC) from a single panel to alternating current (AC). When used, each panel will have its own individual microinverter, instead of a series of panels sending DC current to a central string inverter.


Another name for a solar panel.

Monitoring System

Web-based applications that monitor the performance of your system in real time, highlighting daily production and providing ongoing summaries.

Mono-Crystalline Silicon

Used in manufacturing of high performance solar cells to make longer-lasting and more efficient panels that are also more expensive. Circular wafers are cut from a piece of continuous cylindrical crystal. Also referred to as single crystalline or c-Si.


New York State Energy Research and Development Authority is the entity that provides the per watt utility incentive for New York state (except in LIPA territory).


The process used by utilities to monitor an account’s energy production (which receives a credit) versus an account’s energy usage (which is charged).


New Jersey Clean Energy Program is the entity that provides the per watt utility incentive for New Jersey.


A small converter attached to each individual panel that increases energy output and allows each panel’s performance to be monitored. Optimizers are similar to microinverters, but do not convert DC to AC and are still used with string-inverters.


A particle of light that acts as a unit of energy


Comes from the greek roots photo meaning “light” and volt referring to “electricity.” It refers to the phenomenon of light being converted to electricity and is often abbreviated as PV. Installations are often referred to as Solar Photovoltaic Systems or Solar PV Systems.

Polycrystalline Silicon

Cells are made from large blocks of silicon that are first melted, then carefully cooled and solidified in cast square bars called ingots. These cells are less expensive to produce than single crystal silicon cells, but are less efficient. Also referred to as multicrystalline, poly-Si or mc-Si.


The rails to which solar arrays are mounted. These are typically made of extruded aluminum but some systems use galvanized steel.  Racking is attached to the roof, and then modules are bolted down to these structures.


A system attached to the roof of a building, as opposed to an array installed on the ground.


Solar Renewable Energy Credit, a credit earned for each 1000 kWh of solar energy produced which can later be sold or traded. Price fluctuates according to supply and demand and is managed by state incentive programs.


A series of connected solar panels.

String Inverters

An inverter receiving and converting direct current (DC) from a string of panels to alternating current (AC) that will be used to power the building.

Thin-film panels

Panels made with a thin layer of photovoltaic material making an inexpensive panel with a low efficiency.


An array built on an axis system that allows the panels to tilt and rotate, following the sun’s path over the course of a day and allowing for maximum energy production.


The piece of silicon (typically square or circular) used to make a solar PV cell.

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