Solar Definitions and Vocabulary – Your Solar Dictionary

Non-Technical, Plain English Definitions for Solar Energy Related Terms (with photos to help!)

Here’s an ever-growing list of definitions for words related to solar energy and solar power. If you’re looking for an easy-to-understand solar energy dictionary, and are tired of super-technical definitions that require you to go look up a bunch of other words just to understand the first one – your search is over!

Also – we understand that acronyms (like ITC) help almost no one except experts in a field. So this list includes common solar acronyms like PV and REAP.

Special note to users: If any of these definitions are still too hard to understand for a non-expert in solar energy, please email us and let us know, and we’ll find a simpler way to explain them!

The Layman’s Solar Glossary:

Click on a letter below to find a specific letter, or scroll through to read all the definitions.


















A – Solar Dictionary

photo of solar array on poultry houseAccelerated Depreciation – a government tax deduction that applies the first five years after you install new solar panels. The amount of the tax savings varies by year, and is based on the size of the solar installation.

For more on solar tax incentives, go here for federal solar power tax incentives and here for Georgia solar power tax incentives.

Alternating Current (AC) – electricity that switches the direction it travels in. In the US, the flow of electric current coming out of your wall changes direction once per second. So every minute, it changes direction 60 times. This is safer and more efficient than Direct Current (DC).

Ampere (amp) – the unit for electric current, measuring flow of electrons over time.

Array (Solar Array) – all the solar panels in a solar installation. For example, this picture at right shows a solar array on the roof of this poultry farmhouse. Solar arrays can be on the roof or installed on the ground.

Azimuth – the angle your solar panels face from a bird’s eye view. For example, a panel facing east has an azimuth of 90o. South is 180o, and West is 270o.

B – Solar Dictionary

Backsheet – the ‘backside’ of a solar panel. It protects the inner parts of a panel from moisture and UV light, which over time can reduce the efficiency of a panel. High quality backsheets are important in assuring your panels last through at least the 25-year warranty.

BIPV – Building-Integrated Photo Voltaic. This refers to a group of solar panels installed on a roof or perhaps a side wall, as opposed to on the ground. It is a solar array attached to the building.

C – Solar Dictionary

photo of solar cell, circled, is one part of solar panelCell (Solar Cell) – each section of a solar panel that converts an amount of sunlight into energy. Solar cells are connected to make up a solar panel. See photo.

Central Inverter – See inverter

CIGS – Copper Indium Gallium Deselenide. This is a newer type of “thin film” solar panel that gets better efficiency than other thin film panels.

See this page for more on different types of solar panels.

Crystalline Silicon (C-Si) – a general term for the most common types of solar panels, which are made of silicon. See polycrystalline and monocrystalline for more details.

Current – the flow of electrons. When sunlight hits a solar panel, it causes electrons to flow. This electric current gets turned into energy to power your home, business, or farm.

Get a simple solar energy tutorial – in easy, non-tech language.

Cycle – a battery term meaning one complete discharge and recharge of a battery. A solar battery “filled” up to its maximum capacity that gets used and then recharged by the sun has gone through one cycle.

D – Solar Dictionary

Direct Current (DC) – electricity that flows in the same direction, continuously. Solar panels produce DC electricity. Batteries use DC as well.

DNI – Direct Normal Irradiance. The amount of sunlight that ‘hits’ a location each day. This number helps solar installers predict how much energy you’ll get from your solar panels. In more technical language, this is the amount of solar energy that falls per square meter, per day at a specific location. For example, a DNI of 5 means 5 kiloWatt-hours of solar energy hits each square meter per day. A higher DNI means more energy.

Distributed Power Electronics – this is a category the solar industry uses to include all microinverters and power optimizers.

E – Solar Dictionary

Electrical Grid – the local system of interconnected power lines and equipment that produce and distribute power to all the nearby users, including farms, homes, and businesses. Solar panels can be connected to the grid (on-grid) or completely separate from it (off-grid).

G – Solar Dictionary

this ground-based solar array powers the barn it’s attached toGround-based Solar Array – the alternative to installation panels on your roof. A ground-based array usually sits on poles of racks near the buildings for which they provide power. See photo.

Grid-Connected System – see On-Grid

I – Solar Dictionary

Inverter – a required part of any solar installation, the inverter makes the energy collected by solar panels usable by your home, farm, or business. Also known as a Central Inverter. In more technical language, the inverter converts direct current (DC) from the solar panels into the alternating current (AC) that your power outlets can use.

Inverter Efficiency – how well your inverter turns DC into AC without losing too much energy. Small losses here can add up to big money lost over the 25-year lifespan of your solar panels.

ITC – Investment Tax Credit. This is a federal tax incentive for installing solar panels. Right now, the ITC gives you a 26% total credit for the entire solar installation process.

K – Solar Dictionary

Kilowatts – 1000 Watts. See Watts. How this relates to solar energy: A 5kW solar energy system produces 5 kW per hour of direct sunlight. So if you have 5 hours of direct sunlight per day, your system would produce 25kW per day.

Kilowatt-hours (kWh) – the amount of kilowatts produced or used per hour. You can see this unit on your monthly power bill to see how much power you’re currently using.

Learn how many kWh an average house uses.

M – Solar Dictionary

Megawatts – 1000 kilowatts. See Watts.

Microinverter – does what an inverter does, but for each solar panel rather than the whole system. A microinverter turns solar energy into a form that your home, farm, or business can use – from each solar panel. They are similar to power optimizers in their purpose: Reduce energy losses to things like shade, soiling, and other parts of a panel that stop working.

Mismatch – when one part of a solar panel produces a different amount of energy than another part. This condition reduces efficiency for the whole panel. It can be prevented by using microinverters and power optimizers.

See how much more energy you can get by using microinverters and power optimizers by using the PV Watts calculator.

Module (Solar Module) – another word for a solar panel.

Monocrystalline Silicon – one of the most commonly used types of solar panels. Made of silicon, these crystalline panels last a long time and are the most efficient ones on the market. They are a single crystal of silicon, and usually look like circular cells in the solar panel.

N – Solar Dictionary

Net Metering – an agreement with your power company that allows you to “sell” excess solar energy to them, and lets them charge you for energy you use when your solar energy isn’t enough for your needs. It’s a partnership that keeps you connected to the grid and assures you of steady power. Not all states allow net metering.

O – Solar Dictionary

On-Grid – solar energy systems that are connected to the power grid. This means your power company can still supply you energy if your solar panels don’t produce enough. It also means you can produce excess energy, and if allowed, sell it to the power company.

Off-Grid – solar energy systems totally disconnected from the power grid. This is true energy independence. But if your off-grid system doesn’t produce enough for your needs, you’ll be in the dark.

Compare the pros and cons to on-grid and off-grid solar here.

P – Solar Dictionary

Peak Shaving – reducing how much energy you use during “peak” hours, when utilities tend to charge higher prices. Peak hours are usually from noon to 6pm.

PV – Photo Voltaic. The commonly used name for solar panels in the solar industry. You could say PV panels, PV cells, PV modules, PV array. Same as using “solar” in those instances. What does ‘photo voltaic’ mean? It’s a scientific term that describes how solar panels turn sunlight into energy. ‘Photo’ refers to photons, which are “packets” of light that hit a surface. ‘Voltaic’ refers to voltage and electricity, which is what the solar energy becomes. So, a PV panel turns sunlight into electricity.

Visit this page for a simple solar energy tutorial – in easy, non-tech language.

Polycrystalline Silicon – the most commonly used type of solar panel. Made of silicon, these ‘crystalline’ panels get high efficiency and last a long time. Similar to ‘monocrystalline silicon,’ though a bit less efficient, these are made by crushing silicon crystals into smaller bits. They usually look like rectangles in the solar panel.

Visit this page to compare types of crystalline panels, as well as thin film.

Power Optimizer – an add-on component to solar panels that boosts efficiency and helps reduce losses to things like shade, or if another part of the solar panel gets damaged or stops working.

R – Solar Dictionary

racking for a rooftop solar array on a stadium gets installed in preparation for the panelsRacking – what solar panels are placed on when installed on a roof. The racks are bolted to the roof, and the panels are connected to the racks. Different types of racking, and the space between the racks, may be necessary depending on the type of roof and other factors. See photo, showing the roof of a stadium being racked.

REAP Grant – Rural Energy for America Grant. This grant is available for certain farms, agricultural, and other rural businesses that make energy improvements, including solar panels. The grants can cover as much as 25% of solar installation costs for qualified applicants.

REAP Loan – Like the grant, this is a loan meant to accomplish the same goals, except you do have to pay it back. But it makes the initial installation far more affordable. Both the loan and the grant are exceptional opportunities for farms and agricultural businesses looking to go solar.

Find out more about REAP grants and loans here, and see a case study

S – Solar Dictionary

solar battery storage unit, lithium iron phosphateShading – when all or part of your solar panels are covered by a shadow. Shade reduces the energy a solar panel can collect.

Solar Array – see Array

Solar battery – a battery that stores excess solar energy. If your panels collect more energy than you use, that energy either gets wasted, or sent to the grid if your power company allows it. A solar battery makes it possible to use all your solar energy, even at night, and store it up for darker winter months.

Learn more about solar storage batteries

Solar Cell – see Cell

Solar energy – Any energy collected from the sun. Even plants use solar energy. The solar energy industry is humanity’s attempt to do the same thing – collect and use energy from the sun to provide for our power and electricity needs.

Solar farm – A large-scale collection of solar panels. These are usually on the ground and use lots of acreage. They are usually owned by regional power companies, or very large private companies with massive power needs.

Solar panel – the commonly seen rectangular flat sheets that connect together and collect energy.

Soiling – the collection of dust and debris on your solar panels, which prevents the sunlight from impacting those sections of the panel. You can prevent solar efficiency losses from soiling by regular cleaning and solar maintenance.

System losses – Any losses of energy from what was originally collected from the sun by your solar panels. Losses can happen in all sorts of ways, many of them unpreventable. But some can be reduced, such as shading.

T – Solar Dictionary

Thin-Film – a certain kind of solar technology that is much thinner than the most common crystalline types. Thin film is less efficient, but also less costly.

Visit this page for more on thin film solar panels compared to crystalline panels.

Tilt – the angle of your solar panels compared to the ground, not your roof. A 90o tilt would mean the panel stands up vertically. Typical tilts are between 20 – 40o, though there are many factors that affect this, the main one being your roof.

Tracker – solar panels equipped to adjust their position based on how the sun moves across the sky. They “track” the sun’s position as it changes by the day and by the season. These panels get more direct sunlight each day and therefore produce much more energy. Two types of trackers are available: ones that adjust only on one axis, and those that adjust on two (vertical and horizontal).

U – Solar Dictionary

UV light – Ultraviolet light. The sun’s visible light is only one portion of the radiation it produces. UV is an unseen part of the sun’s energy, but it still affects solar panels.

V – Solar Dictionary

Voltage – the ‘force’ required to move electrons. Without voltage, there is no current. Without current, there is no electricity.

Visit this page for a simple solar energy tutorial, including more on voltage – in easy, non-tech language


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