This page is to all things solar panels as the dictionary is to any term you could look up in your native language. Look no further for clear and concise definitions of solar terms. If you still have questions about the meaning of certain terms or do not see the term for which you are searching on this page, send us an email at firstname.lastname@example.org and we will make sure we answer your question(s) and include an updated definition for the term in question, or you can visit our Solar Dictionary Blog Posts in the Frequently Asked Solar Questions portion of our blog.
General Solar Terms
These are some of the common terms used throughout the solar world. Having a good foundation in general solar terms is the best way to not get lost during the solar process.
Solar Power Vs. Solar Energy
Solar Power: The transformation of solar energy into electricity.
Solar Energy: Energy produced by the sun.
Solar Array: All the components used to change light into usable electricity from solar technology.
Photovoltaics (PV): A device that creates electricity from sunlight using semiconductors.
Watt: A unit of power used to measure electricity. A watt equals one joule per second. Solar panels typically describe how much power they can produce in watts.
Module: A single solar panel.
Electric Current Types
Alternating Current (AC): A current that systematically switches direction. This current type is common in homes.
Direct Current (DC): A current that only moves in one direction. Solar panels produce direct current.
Thermal Solar Panels: Technology that captures heat from the sun, which then generates electricity or heats something else.
Conductor: A material that allows electricity to flow with ease.
Insulator: A material that blocks electricity.
Semiconductor: A material that can produce electricity under certain conditions. Certain doped semiconductors are ideal for solar because they can generate a current from sunlight.
Solar Cost, Savings and Financing
Knowing the ins-and-outs of financial talk is crucial when making a big investment. Going solar is no exception.
Solar Panel Owning: There are two different ways for solar customers to own their solar array. Customers can pay cash or they can get a solar loan.
Solar Loan: A loan program offered by the solar company through a loan partner that the solar company works with and trusts. They allow the customer to get into solar without having to make a large upfront payment or go through the hassle of finding a loan officer.
Personal Loan: A loan type that comes with fixed rates and fixed monthly payments. They are unsecured, which means the lender doesn't need collateral for the loan.
Home Improvement Loan: A type of personal loan used for home improvements, under which category solar panels can be categorized.
Home Equity Loans: This loan type allows a homeowner to borrow against the equity in their home.
Home Equity Line of Credit (HELOC): Also known as HELOC. This financing option is a line of credit against the equity in the home. It works similar to a credit card and often has a variable interest rate.
Mortgage Loans: These loans can cover the cost of a home and solar or any other home improvements. The two mortgage loans offered include FHA and Fannie Mae loans.
Solar Panel Leasing: The process of a solar customer entering into a lease for their solar installation. Solar leases typically have longer terms and lower monthly rates. Homeowners do not own the solar array on their roof when they agree to a solar lease.
Power Purchase Agreement (PPA): This is similar to a solar lease. With a PPA, a developer owns, installs, and maintains the solar array on the customer's home. The customer then pays a low monthly rate to the solar company for the electricity the array produces over 10-25 years.
Solar Cost Terms
Electricity Prices: The rate that local utilities charge customers for electricity. Utility prices for electricity are the reason why solar arrays can save customers money.
Cost Per Watt: The total cost of the solar installation divided by the size of the array. Cost per watt helps customers find the comparative cost of solar.
Levelized Cost of Energy (LCOE): This includes all the operating costs that go into maintaining a solar array. It covers everything from the initial cost and interest to the maintenance and expected solar generation for the system.
Comparative Cost of Solar: The cost of solar compared to the cost of fossil fuels. The comparative cost of solar is often the measure that solar proponents use to determine solar savings.
Inflation Rate: The fluctuating value of the dollar over time. The buying power of the dollar goes down as it continues to inflate, making the cost of living more expensive over time. While inflation negatively impacts utility rates, homeowners can sidestep the issues of inflation and fluctuating utility company rates by locking in a fixed payment on their solar systems over the lifespan of their arrays, many of which are warrantied at 80 percent production for the first 25 years and last as long as 50 years.
Payback: The time it takes for a solar array to pay for itself in savings. Also known as a break-even point. This term is equivalent to solar panel ROI.
Solar Product Warranties
The solar product warranty generally protects the customer from acquiring any extra costs for products damaged by the manufacturer, the weather or wear and tear during the warranty period.
Performance Warranty: This is the promised performance from the manufacturer.
Solar Workmanship Warranty: This is a warranty that covers the design and installation of the solar array.
Homeowners Insurance: Covers the cost or the majority of the cost when a home is damaged. Homeowner's insurance policies can often add solar arrays without any extra charge, but it is best to check the policy first.
Solar storage is a key part of any solar installation. With more and more Americans choosing energy independence, we put together a handy guide to the words and phrases of solar storage.
Backup Definition and Options
Backup: Any form of power used when the homeowner’s main source of power goes out.
Generators: A backup option that is typically powered by fossil fuel. They transfer mechanical energy into electric energy. One of the main differences between a generator and battery backup is that one stores power while the other generates it.
Battery Backup: A battery designed to store solar, so the homeowner can access their excess electricity when they need it without having to pay extra for it.
Tesla Powerwall: A home battery designed by Tesla. It can be used to power a home in an emergency, or even regularly.
Home Battery: A battery designed to hold enough power to power home over an extended period.
Goal Zero Yeti: A portable solar battery designed to provide easy access to power for essentials at all times.
Solar Panel Maintenance
This is the post-installation care needed for a solar array to function at its prime. Because there aren’t any moving parts on a solar array, the only maintenance that a solar homeowner might want to consider is washing or removing snow from their solar panels. Snow melts off, for the most part, but a bad storm might require snow removal. On the same note, natural rainfall takes care of most of the build-up on solar panels throughout the year but cleaning them at least once a year will increase their performance.
Winter Maintenance Item
Roof Rake: A tool designed to clear snow from solar panels in the winter. This tool allows the user to clear the snow without being on the roof. The roof rake design protects the panels from being scratched by the tool.
Fall/Spring Maintenance Devices
Telescopic Pole: A pole with extension capabilities, allowing the user to reach higher spots from the ground. Water-fed telescopic poles make cleaning tough spots on solar panels easier.
Solar Panel Cleaning Robot: These are robots programmed to clean solar panels. Like an automatic car wash, they do a decent job and often get most of the grime, but they can’t detect if a spot was missed or needs more attention. Cleaning robots are often part of the maintenance plan for utility-scale solar farms.
Reverse Osmosis Water: The removal of minerals that cause hard water from the water. Water that has gone through this process will wash solar panels better than an average garden hose can.
Deionized Water: The removal of ions from water. Removing ions from water increases its attraction to objects with an ionic charge, such as dirt, which makes the cleaning process faster.
Water Fed Brush: A brush that can hook up to a hose and is used as an extension to the hose. The brush also allows the user to better scrubs solar panels that need more than a rinse.
Technical On-The-Panel Terms and Factors
While many solar homeowners aren't interested in the nitty-gritty details of the solar process, we believe in openness and transparency. We put together a list of some of the more technical terms used in going solar to make sure that you never feel lost or overwhelmed.
Solar Panel Production Standards: The expected production and degradation rate of the solar panel. Together, these two factors predict the electricity production of a solar panel in perfect conditions.
Annual Degradation: The rate to expect solar panel production will decline per year. All electronics decline over time. However, finding a solar panel with a low degradation rate will help. Although one percent is the standard degradation rate, in 2012, the NREL found that panels made before 2000 had a rate of 0.5 percent, and panels made before 2000 had a degradation rate of 0.4 percent. While there are warrantied degradation rates on most solar panels, the actual rate of degradation will depend on the climate. Panels installed in moderate climates, like the northern United States, have an average degradation rate of 0.2 percent, while panels that are exposed to extreme temperatures most of the time are closer to one percent.
Maximum Power (Pmax): The highest amount of electricity that a solar panel can produce under standard testing conditions.
Power Tolerance: How much a solar panel can differ from the Pmax during standard testing conditions. There is a positive and negative power tolerance for each solar panel. The measurement of these tolerances is typically a percentage of the total power output of watts. If the solar panel performs higher or lower than the power tolerance, a Pmax warranty may cover the solar panel.
Maximum Power Point (MPP): When the product of current and voltage of a solar panel have reached their highest point. Sometimes this is also referred to as the maximum power.
Maximum Power Point Tracker (MPPT): A device that helps solar panels produce at their MPP even when the conditions aren’t optimal. Also known as maximum power tracking.
Operating Temperature: The temperature where the solar panel functions best. Solar panel tests are typically at 77 degrees Fahrenheit. They often perform best between 59 and 95 degrees Fahrenheit.
Module Efficiency: The efficiency of a single solar panel. Each solar panel plays its part in the efficiency of a solar array.
Solar Cell: The part of a solar panel that turns sunlight into electricity. It is composed of three layers of semiconductor material that collects specific wavelengths of light, which knocks electrons in the cell loose so an electric current can form.
Power Optimizers: A device placed on each solar panel to help decrease the impact one shaded solar panel has on the production of the entire array by increasing the amount of direct current each panel produces. They help solve string inverter issues. Also known as DC power optimizers.
Material Absorption: The amount and type of light wavelengths a semiconductor material in a solar panel can soak up and convert into an electric current.
Ingot: A molded structure typically out of a semiconductor material such as silicon. Ingots are later thinly sliced into wafers and put in solar cells so a solar panel can absorb light wavelengths from the sun.
Wafer: Wafers are a slice of the semiconductor. Wafers in solar panels capture wavelengths from the sun. The material of your semiconductor will determine how well it will collect wavelengths. Most wafers use silicon. When wafers get cut, a waste silicon slurry with impurities forms. Separating and recycling silicon and carbide silicon will help protect the environment.
Back Contact: A thin layer of conductive material is screen printed on the back of the solar cell to help the electrons flow from one cell to the next. Solar cells that only have a back contact have the potential to be more efficient because the strips of metal don’t shade the cell.
Front Contact: Thin strips of conductive material placed on the front of the cells to allow the electricity to flow from one cell to the next.
P-Type Semiconductor: This is the bottom section of a solar cell. This section contains a semiconductor, such as silicon, doped with an element with fewer electrons than the semiconductor, such as boron, known as a trivalent impurity. The missing electrons in the impurity give this section a positive charge. The P-type semiconductor collects and transports positive charges, also known as holes.
N-Type Semiconductor: The top section of a solar cell. The N-type semiconductors contain a semiconductor, like silicon, doped in a pentavalent impurity, such as phosphorus, that has more electrons than the semiconductor.
Doped Solar Cell: When a semiconductor, usually used in a solar cell, has impurities added to it to change its electrical charge.
Temperature Coefficient: The change in a particular physical property per Celsius degree.
Solar Array Operating Voltage: The voltage an array will produce when installed and running.
While knowing all the words and phrases of solar panels is an achievement itself, there are factors that don't deal with solar panel hardware. Below are some terms which are used to describe other parts of the solar process.
Passive Solar: Passive solar is the process of designing buildings and homes to collect, store, reflect, and distribute solar power depending on the season and other infrastructural factors not creditable to the solar array itself; e.g., harnessing windows, walls, and floors to control the building's environment.
Global Horizontal Irradiance (GHI): The total shortwave radiation that an object horizontal to the ground receives, which includes both the direct normal irradiance and diffuse horizontal irradiance.
Direct Normal Irradiance (DNI): Only measures the radiation coming from the sun. Tracking the radiation on a surface that is always perpendicular to the sun produces this measurement.
Diffuse Horizontal Irradiance (DHI): Measures the scattered light wavelengths that an area receives. Often these light wavelengths are scattered by particles in the air.
Solar Tilt Angle: The vertical angle of the solar panels. This angle is also known as the elevation angle.
Azimuth: A calculation of the angle of the sun to a horizontal plane.
Solar Orientation: How a building lines up with the sun. Areas that face the south receive the most sun exposure. However, solar panels placed on the east or west side of a home have sunlight as well. Solar panels should never face north.
Peak Sun Hours: The average hours in a day that receive the most direct sun exposure.
Panel Recycling: The act of taking old or broken solar panels and separating their parts for reuse in other solar panels. Europe has a developing recycling program, and America is starting to increase its focus on solar panel recycling as well. Although currently, solar panel recycling is a con, the industry expects production to increase as more solar arrays come closer to their expected expiration.
HOA (Home Owners Association): Homes under an HOA's jurisdiction may have to follow different processes for solar panel installation according to their HOA's guidelines.
Solar Installer Terms
Go Solar Group wants to make sure that all solar-curious homeowners know the basics of installer terminology. By doing so, we can avoid potential miscommunications.
Solar Installation Steps: A combination of permits and permissions that a solar company needs before they can install a solar array. A quality solar installation guide will show the order of these steps and the time frame to expect.
Solar Referral Programs: An incentive program that a solar company offers to individuals who refer their friends and family to the company.
Solar Installer: An individual or group of individuals trained to work with, and install solar panels. Not all solar companies are solar installers. Some solar companies hire contract solar installers to install the arrays.
Full-Service Solar: A solar company that takes care of pre-installation, installation, and post-installation work in-house. Customers that choose a full-service solar company don’t have to worry about any portion of their solar experience.
Solar Contractor: A solar professional hired to install, maintain or repair solar panels. Contractors are not company employees. Often solar companies hire solar contractors when they don’t have the resources or need to hire an employee to do it regularly.
Solar Installation Types
Solar can be installed in many different settings, from residential to commercial and beyond. These are some of the ways in which solar is utilized by the wider world.
Residential Solar: Solar panels purchased by homeowners and placed on the roofs of their homes or their property for personal use. Solar companies that specialize in residential solar provide homeowners with personal-use solar arrays.
Commercial Solar: Solar panels produced and purchased for small businesses and large corporations. Business owners can save immensely on their electricity bills when they install commercial solar on their buildings or property.
Utility-Scale Solar: Solar panel installations that can produce the amount of power needed for a utility company to power cities.
Solar Farms: An area set aside for a large amount of ground-mounted solar panels. Solar farms are often how utilities obtain solar power for their customers.
Dual-Use Farming: The act of combining the property solar farms are on with agriculture. Certain plants and pollinators thrive under the shade of solar panel farms, which is another reason why solar benefits this industry.
Community Solar: A solar farm designated for residential use. Community members agree to participate in, and receive the tax benefit from, a community solar farm.
Concentrated Solar Power (CSP): A form of solar that uses mirrors or lenses that aggregate large areas of sunlight into receiving modules.
Utility Company Types Relevant To Solar
There are many types of companies present in the solar world, each with their own niche. Here is a basic rundown on the main kinds of solar companies you may run into.
Regulated Utility Company: A utility that has full control over the generation and distribution of the electricity in the area that it services.
Energy Deregulation: When companies that only own the generation of its power and not the method of distribution, such as power lines, are allowed into the market. The electricity market in most of Texas is an example of energy deregulation.
Municipal ("Muni"): A utility company owned and operated by the city.
Cooperative (coop): A utility owned and operated by elected community members.
Investor-Owned Utilities: Utilities that are privately owned and operated.
Solar Panel Mounts
Solar panels need to be mounted to something in order to stand at the right angle. Listed here are some of the different mounting types, each of which has its own purpose.
Ground Mount: A ground-level foundation and attached structure designed to support solar panels in various weather conditions. Typically ground mounts will hold a group of solar panels about two or three feet off the ground.
Ballasted Mount: A device that holds solar panels in place on a flat roof without puncturing the roof. Ballasted mounts are often held in place by cinder blocks.
Pole Mount: A pole that holds several solar panels in the air. Installing a pole mount is an extensive and expensive process, but it takes less room than a ground mount.
Solar Shingles: Small solar panels made to blend in with the roofing shingles. Because solar shingles are smaller than the typical residential solar panel, a homeowner needs more shingles to get the same amount of solar power for their home.
In-Roof System: A solar array installed into the roof of the home. In-roof system installations typically happen with the installation of a new roof.
On-Roof System: A system installed on top of a home's existing roof. On-roof systems are the most common residential solar installation type.
Solar Tracker: A system that follows the sun throughout the day or moves seasonally to optimize the production of solar panels.
Fixed Tilt Array: An array set at an optimal position that doesn’t ever change.
Rooftop Solar: A solar array installed on the roof of a home or company.
Solar Industry Entities and Acronyms
Many are scared of learning the alphabet soup of various companies, government agencies, and acronyms. However, many of these acronyms are important for solar homeowners to learn. We've compiled a cheat sheet of all the main acronyms that you need to learn, which you can reference whenever you feel confused.
SEIA (Solar Energy Industries Association): SEIA is a non-profit trade association for the United States solar industry.
NABCEP: The North American Board of Certified Energy Practitioners. A non-profit solar professional certification organization. They provide certificates and accreditation to solar professionals across America. Make sure your solar installer has installers with the PV designation.
ITC: The Investment Tax Credit is a solar credit taken out of the federal taxes that the customer would have owed. Individuals that do not owe federal taxes do not qualify for this solar incentive.
kWh: kilowatt-hour or kilowatts per hour. This measurement is equal to 3.6 megajoules. This measurement measures electricity usage — 1 kWh equals 1,000 watts of electricity.
DSIRE: DSIRE is a database that keeps track of the renewable energy incentives offered in each state.
GHI: See Global Horizontal Irradiance
DNI: See Direct Normal Irradiance
DHI: See Diffuse Horizontal Irradiance
AC: See alternating current
DC: See direct current
PPA: See Power Purchase Agreement
Amp: Also known as ampere. An ampere is a unit that measures electric current. One can find the wattage of a solar panel by multiplying the amps by the voltage of the solar panel.
HELOCs: See Home Equity Line of Credit
NREL: Stands for National Renewable Energy Laboratory. The NREL is a national laboratory funded by the U.S. Department of Energy and operated by the Alliance for Sustainable Energy.
AH: An amp-hour. An amp-hour is the measurement of how many amps used in one hour. Multiplying the amps used by how many hours used equals an amp hour.
LCOE: See Levelized cost of energy
IEEE: Institute of electrical and electronic engineers. This organization focuses on worldwide technology advancement.
NEC: National electrical code. Solar installers need to adhere to the most recent version of the NEC implemented in the state they are servicing.
STC: Standard Test Conditions. These are the industry standards for the testing environment solar panels go through, which insure solar panel reliability. There are three STC, which include the temperature of the cell, solar irradiance and air mass.
PTC: PVUSA (Photovoltaics for Utility Scale Applications) Test Condition is a rating system developed to determine and evaluate the performance of commercial use photovoltaics. Because the temperature standard for these test conditions is closer to real weather conditions, these standards are considered more realistic. The PTC uses a baseline temperature of 20°C and the normal operating cell temperature at 45°C.
DOE: The Department of Energy. Focuses on policies regarding energy and safely handling nuclear materials.
MACRS: The Modified Accelerated Cost Recovery System is a tax depreciation system that pays companies the estimated depreciation of certain tangible property through annual deductions on their owed taxes. Business owners with a qualified solar array can receive the MACRS for five years.
RPS: See renewable portfolio standard
PEC: See Portfolio Energy Credit
Solar Panel Types
Solar panels are broken down into many categories, each with their own unique traits. Below are each of the major types of solar panels.
Monocrystalline Solar Panels: Solar panels with cells cut from a single crystalline silicon ingot, meaning the cell is less likely to reflect the light that hits it. Monocrystalline solar panels often produce the most power per panel.
Polycrystalline Solar Panels: Solar panels with cells made from several silicon fragments melted together. Polycrystalline solar panels often have a blue hue.
Thin Film Solar Panels: Solar panels with solar cells are made by putting a thin layer of photovoltaic material on another, thicker material. Often the cells in thin-film panels are made of glass plastic or metal.
Handheld Solar Panels: Solar panels made compact enough that you can hold them in your hand or put them on a backpack. These are often called solar chargers. They can absorb enough sunlight to charge a phone or a tablet while going on a hike.
Portable Solar Panels: Panels that can someone can carry with ease. Some portable solar panels are larger, but have a portability feature, while others are small enough to lay across a rock and soak up the sun.
Utility-Based Solar Programs
Many state and local utilities offer solar incentives for homeowners. We've listed some of the main programs for our market below.
Rocky Mountain Power’s Transitional Program: A solar net metering program that Rocky Mountain Power agreed on in 2017. The transitional program meters customers every 15 minutes and pays 90 percent of the retail rate for excess solar power put onto the grid. This program ended in 2020 and Rocky Mountain Power implemented a new net metering rate.
NV Energy Solar Generations Program: An incentive program provided by NV Energy. The Solar Generations Program offers incentives for both commercial and residential-scale battery backup and solar arrays, but not all the local installers in its service area have products that qualify for the program.
PNM Solar Generation Program: Through this program PNM offers New Mexicans compensation for RECs and net metering.
Net Metering Terms
Net metering is an important part of going solar, but it can be confusing to new solar homeowners. These terms can help you understand just what net metering is and how it can help you.
Interconnection: defines how solar customers can leverage the grid and financially benefit from selling power back to power companies.
Net Metering: A program for solar customers that allows them to sell their excess solar power to their local utility company. Net metering is a billing system that allows solar customers to utilize all of their generated solar power, instead of only what is used during the day.
Feed-in Tariff: A billing system that pays renewable generation customers a fixed rate for the excess electricity they put on the grid. Feed-in tariff rates normally last for 10-20 years.
Renewable Energy Blockchain: Blockchain is a database that stores and processes transactional information from cryptocurrency. In the renewable energy sector, blockchain could track renewable energy credits or allow neighbors to trade their generated electricity among each other.
Bi-Directional Meter: A meter that measures both the electricity pulled off the grid and the excess generated electricity put on the grid.
Dual Meter: When one meter tracks electricity going on the grid, and another meter tracks the electricity pulled off the grid.
Usage: The amount of electricity consumed by a utility customer. Usage is on monthly electricity bills, but sometimes must be distinguished between gas consumption and electrical consumption. Solar homes require a certain amount of usage for an installation to make financial sense.
Solar Policy Terms
Renewable energy has long been a focus of local, state, and federal legislatures. To help you understand their legal policies and programs, we've compiled some of the basic terminology used in solar law.
Renewable Energy Portfolio: A goal or standard a state creates for renewable energy production.
Renewable Portfolio Standard (RPS): A state-required mandate that requires a certain percentage of electricity generation to come from renewable energy.
Renewable Portfolio Goal: A target for renewable energy generation in the state. A renewable energy goal has nothing in place to enforce the desired renewable energy production that the state has determined they want to reach.
Solar Carve-Out: A specific goal set within a renewable portfolio standard that determines how much electricity the state would like to generate from solar.
Solar Rebates: Financial incentives paid to utility customers who are installing solar. Rebates typically come from the federal, state or city governments and are distributed through the local utility.
Solar Incentive: A motivating reward for installing solar.
Tax Credits: An incentive in the form of a reduction to the taxes the array owner owes to either the federal or state government.
Performance Payment: An incentive that rewards homeowners for electricity production.
Renewable Energy: Most often used with legislation or policy-based changes, in which solar is grouped with wind, geothermal and hydropower.
Portfolio Energy Credit (PEC): A PEC, also known as a Solar Renewable Energy Certificate (SREC), is a credit associated with a certain amount of produced renewable energy. Credits go to the energy producer, but trading them is common. The credits help the government track energy production in the state and incentivize utilities to invest in renewable energy.
There's more to solar than just panels. In this category, we've listed some of the main compliments to solar energy, which you can use to save even more money.
Smart Meter: An electronic meter that can report the electricity reading to the utility. This type of meter eliminates the need for the utility to physically come out and read the meter each month. It also provides real-time data so the utility can detect grid failures and charge customers accurately.
Smart Thermostat: An electronic thermostat that can report energy data to the customer and is controlled remotely through a phone or computer, e.g., The Nest Smart Thermostat.
Solar Shades: A window covering that lets in partial light while blocking heat; solar shades are mainly used in extremely hot markets.
Energy-Saving Windows: These are windows designed to keep air from escaping to either side of the window.
Solar Screens: Special screens installed on the outside of the home to help decrease the heat that enters the home.