Glossary of Solar Terms

AC

AC refers to the alternating current of electrical energy. When solar panels absorb sunlight, they produce direct current (DC) electricity, which goes to either a solar battery or inverter. If electricity goes to an inverter, DC electricity converts to AC electricity. Homes and businesses can use this AC electricity, or it can go to the grid. 

Array

A solar array is a group of photovoltaic (PV) modules (i.e., solar panels) that make up an interconnected system. These modules function as a single unit to produce energy, and a mount typically supports them. Small solar arrays may consist of one module. 

Azimuth

An azimuth is the angle between true south and the point in the horizon that’s directly below the sun. Ideally, your solar panels should aim in this direction. 

Ballast Mount

Mounts that directly attach to a home’s rafters support most solar panel systems. However, solar technicians typically use a ballast mount for flat roofs, which include weights to keep the solar panel array in place. Ballast mounts don’t require roof penetration.

BOS

BOS stands for balance of system. It refers to the components required for a solar panel system to function properly and interconnect with the grid (and thus a utility). These components include solar panels, combiner boxes, wiring, switches, breakers, monitoring equipment, a mounting system and more. Your equipment will slightly vary, depending on whether you have roof-, ground- or wall-mounted solar panels. 

DC

DC refers to the direct current of electrical energy. When solar cells (which make up solar panels) absorb sunlight, they produce DC electricity. That electricity either goes to an inverter or a solar battery. An inverter must convert DC electricity to alternating current (AC) electricity before you can use it in your home or business or before it goes to the grid. 

Efficiency

Solar panel efficiency refers to the amount of sunlight energy that solar panels can convert into electricity. The more efficient your panels are, the more usable power you generate for your home.

Electricity Grid

The grid is a system that delivers electricity from power generators to homes and businesses. However, if you own solar panels, you can connect your system to the grid to take advantage of your utility’s net metering program or to source energy when rates are low. You can also rely on the grid if your panels didn’t produce enough energy during the day to power your home. 

Grid-Connected System

Systems that can connect and disconnect from the grid are known as hybrid solar panels. With them, you can rely on both your panels and the grid for power, rather than an off-grid solar panel system that doesn’t allow you to connect to the grid. Additionally, you can send your panels’ excess energy to the grid and benefit from local net metering programs through your utility. 

Interconnection

Interconnection is the link between two utility companies’ transmission lines or between a utility and an end user (e.g., home or business owner). A grid-tied solar panel system is interconnected, but an off-grid system is not. Off-grid solar is risky because if your panels fail to generate enough power for your needs, you can source backup power only from a battery rather than from the grid, too.

Interconnection and BOS Equipment

Interconnection is the link between a utility’s electric supply and an end user via the grid. BOS stands for balance of systems and refers to a solar panel system being connected to a home’s or business’s main electrical service. BOS equipment includes wiring, switches, a mounting system, one or more solar inverters, a battery and more. BOS equipment allows a solar panel system to function properly with all its required parts and components. This functionality then allows the system to connect with the grid and send or receive solar power from a utility. 

Inverters

An inverter converts direct current (DC) electricity that solar panels generate into alternating current (AC) electricity, which you can use for your home. If the grid goes down, modern inverters prevent the electricity coming from solar panels from flowing through the grid. This protects workers making grid repairs during power outages. 

Kilowatt-Hour (KWh)

One kilowatt-hour (kWh) is the measurement of 1,000 watts of power consumption within one hour. This is based on the amount of solar energy you consume rather than produce. 

Meter

Meters measure the amount of power you produce, send to the grid and use in your home or business. Digital meters can track both inward- and outward-flowing energy from your solar panel system to the grid. 

Micro-Inverter

A micro-inverter is a system containing multiple inverters, with one designated for each solar panel. With conventional or string inverters, if one panel goes out, the entire solar panel system goes out, or the system’s overall performance drops to the lowest-performing panel. However, with micro-inverters, each panel functions independently, which enables panel-leveling monitoring. 

Monitoring Systems

Monitoring systems are devices that provide information about your solar panel and energy storage systems. They display the amount of energy you use, how much energy is left in your battery and electricity rates at different times of day. 

Monocrystalline Silicon

Monocrystalline silicon is a type of silicon that manufacturers use to make solar panels. Solar panels made with monocrystalline silicon have solar cells that have only one silicon crystal per cell. These panels are more expensive to purchase and complex to manufacture compared to polycrystalline panels, but they are also more energy- and space-efficient. 

Net Metering

Net metering is a program that local utility companies offer. It allows solar panel system owners to send their excess energy to the grid in return for solar credits. They can use these credits to purchase electricity from the utility if their panels didn’t generate enough power during the day, their battery ran out of stored power or they want to take advantage of low electricity rates. 

Photovoltaic Effect

Photovoltaic effect refers to the process of a solar cell generating electricity from the sunlight it absorbs. More specifically, it refers to the electrical current that a conductor (a solar cell) creates after the sun’s rays (e.g., sunlight, light, photons) strike it. Alexandre Edmond Becquerel discovered this process in 1839 while studying the electrical effects of two electrodes dipped in electrolytes. 

Polycrystalline Silicon

Polycrystalline silicon is a type of silicon that manufacturers use to make solar panels. Polycrystalline solar panels comprise solar cells that contain numerous melted-together silicon fragments. These panels are simpler and more cost-effective to manufacture than monocrystalline panels, but they are also less energy- and space-efficient.

PTO

PTO stands for permission to operate. Your utility company typically grants PTO only after a professional company installs your solar panels. So, as long as your solar panel system meets your utility’s requirements, it’ll then grant you PTO. In other words, with PTO, your solar panels can start generating power for your home or business.

PV

PV stands for photovoltaic. This is the term people use to describe solar PV panels (i.e., solar panels). The root word “photo” refers to light, and the root word “volt” refers to electric potential. When you combine the two root words — photovoltaic — the term represents the electric potential of sunlight (i.e., solar power potential). 

Racking and Mounting

Racking and mounting are the methods installers use to fasten solar panels to a roof, a wall or the ground. Installers use flashings and clamps to arrange and secure solar panels along horizontal rails. 

Renewable Energy Certificates (RECs)

Renewable Energy Certificates (RECs) are also known as solar energy credits, green tags and green energy certificates. They are tradable and represent one megawatt-hour (mWh) of electricity generated from a renewable source. Not all utility companies accept or offer RECs, so checking your local energy provider’s solar rebates and incentives is vital. 

Silicon

Silicon is the element that makes up solar cells. It’s the ideal material for solar cells (which are in solar panels) because it reacts with photons from sunlight, which then produces power from electrons.

Solar Battery

A solar battery is an energy storage device. You can store any excess solar energy that your panels produce in a solar battery and use the energy when needed later. Solar batteries are especially great to have if your region is prone to power outages, your utility offers a net metering program or your panels consistently produce more energy than you need due to an abundance of sunlight.

Solar Energy

Solar energy is a type of renewable energy that’s generated by the sun and measured in kilowatts (KW) rather than kilowatt-hours (kWh). This is because it isn’t usable for a home or business until converted. Solar energy is produced when nuclear fusion takes place between radiant light and heat. Fusion occurs when hydrogen atoms and protons collide in the sun’s core, and then fuse to create a helium atom. A range of modern technologies are used to harness solar energy. For example, solar panels absorb solar energy to generate electricity in the form of solar power. 

Solar Inverter

A solar inverter is a device that converts the solar energy your panels generate into usable energy for your home or business. If you don’t use the converted energy for your own power needs, you can send it to the grid or store it in a backup power solution, such as a Tesla Powerwall.

Solar Investment Tax Credit (ITC)

The solar investment tax credit (ITC) is a federal incentive that allows home and business owners to apply for credits when filing income taxes. The solar ITC is currently 30%, which goes toward the total purchase and installation costs of your solar panel system. 

Solar Panels

Solar panels are also known as solar photovoltaic (PV) panels, which convert the energy the sun generates into electricity. They do this by absorbing photons from sunlight through a material called silicon (which most panels are made of) and creating electricity voltage. Check out this article to learn more: How Solar Power Works. 

Solar Panel Warranty

A solar panel warranty enables home and business owners to protect their purchase from manufacturing defects, weather damage (such as from hurricanes), environmental issues, reduced performance due to age or general wear and more. Freedom Solar offers a 25-year warranty covering the product’s various equipment pieces, its performance and any potentially necessary workmanship.

Solar Power

Solar power is produced when harnessing solar energy from the sun and is measured in kilowatt-hours (kWh) rather than kilowatts (KW). This is because KW energy is direct current (DC) energy, and isn’t usable for a home or business until it’s converted to alternating current (AC) energy (or kWh). For electricity, the solar photovoltaic (PV) cells that make up solar panels will absorb sunlight to generate electrical energy — this is one form of solar power. For heat (or thermal energy), solar energy is harnessed in a more direct way without the use of solar PV cells and panels.

STC

STC stands for Standard Test Conditions. STC are the set of laboratory conditions under which manufacturers test solar modules. Solar panel manufacturers use STC to ensure they can sell, mount and use photovoltaic (PV) panels with similar energy outputs together in a system. 

String Inverter

A string inverter is a device used with solar panels arrays to convert direct current (DC) electrical energy to alternating current (AC) electrical energy. String inverters are connected to each separate panel in an array, forcing the overall performance of your system to be equal to the worst performing panel. And since energy is converted at the end of each row of panels, there is more voltage transferring across your roof, which leads to a higher fire hazard risk. String inverters are cheaper than micro-inverters because less equipment is required, however, the long-term costs outweigh the immediate financial benefits. 

Sun Number Score

A company called Sun Number created the Sun Number Score. The concept is meant to bring awareness to the solar potential of your home or business building. The score considers several factors, such as the region you’re located, your roof’s slope and orientation, and much more. Scores range from 0 to 100 — and the higher your score is, the better.

Tier 1 Solar Panels

Tier 1 solar panels are built with higher standards in order to last longer and produce more solar power (Tier 1 panels are more efficient than Tier 2 panels). For this reason, they’re more expensive than Tier 2 solar panels. Tier 1 manufacturers have typically been in the solar industry for at least five years, and make up the top 2% of solar manufacturers. 

Tier 2 Solar Panels

Tier 2 solar panels are less expensive than Tier 1 panels, but are less efficient at producing solar power. Tier 2 panels have more reports of defects because the companies that produce them have less experience in the solar industry and manufacturing process. 

Watt and Kilowatt (KW)

A watt (W) is a measurement of energy, being one unit of power. One kilowatt (KW) equals 1,000 watts.