Here is a Glossary of Common Solar Terms

Cell: A solar cell is the basic component of solar modules. Cells are manufactured from wafers of industrial grade silicon.

CO2: An abbreviation for carbon dioxide. CO2 is well-known as a “green-house gas.” When people refer to a “Carbon Footprint,” they are usually referring to CO2 emissions.

Energy Payback: The period of time required for a solar panel to generate energy equal to the amount required to manufacture it. Modern PV panels have an energy payback of 1 to 9 years, depending on the type and location of the installation. Over a 30+ year life, a PV system will return 10 to 30 times the energy that went into producing them.

Grid: A network and infrastructure required to deliver electricity from suppliers to consumers. It consists of generating stations that produce electrical power, high-voltage transmission lines that carry power from distant sources to demand centers, and distribution lines that connect individual customers.  This is often referred to as a transportation medium for electrical energy with attendant costs.

Grid-Tied: A grid-connected solar electric system which generates electricity and feeds its excess power into the local utility grid for later use. Grid-connected solar electric systems are eligible for many incentives and rebates.

Gigawatt (GW): A gigawatt is 1 billion watts or enough electrical energy to power 700,000 to 1 million buildings for a year, depending their energy efficiency.  In the USA, renewable energy installed capacity is expected to quadruple from 81 gigawatts in 2011 to 321 gigawatts in 2030.

Inverter: An electromagnetic device which converts Direct Current (DC) power generated by the solar panels into Alternating Current (AC) power.  This device is required for grid-connected solar power systems.  The inverter can be deployed in a variety of ways to meet system configurations.

  • Micro inverters can be attached to each solar module. The cost is typically higher, but they provide advantages for very small, differentially shaded, or geometrically complex PV systems.
  • String inverters are the most common type of inverter for residential and small commercial PV systems.
  • Central inverters are used for very large photovoltaic systems.

Insolation: The level and quality of sunlight varies by region, air quality, season, and latitude.  Insolation is a measure of the solar radiation energy (see irradiance) striking the Earth in a given region.

Irradiance: The measure of energy produced by the Sun on a persistent level.  Irradiance at the solar distance of the Earth’s orbit in a vacuum is calculated to be 1.3kW/square meter.  Normal irradiance at the surface of the Earth is 1kW/square meter.

Kilowatt (kW): A unit of power equivalent to 1000 watts. Relative sizes of PV systems are expressed in kW production.

Kilowatt hour (kWh): unit of energy consumption; energy users are billed on a price-per-kWh basis.

Load profile: The general pattern of electricity use by a home or business over a given period of time. Load profiles help determine the appropriate size of the PV system to install.

Megawatt: The megawatt (mW) is a unit of power corresponding to one million watts. For reference about 10,000 100-watt light bulbs or 2,000 computer systems would be needed to draw 1 megawatt.

Module: Usually 60 or 72 solar cells are combined into a solar module, which is also called a solar panel.  The module output in volts is determined by the cumulative number of cells.

Monocrystalline: Silicon that is manufactured as a single, completely homogenous crystal.

Net Metering:  Net metering, sometimes referred to as "net energy metering," enables solar system owners to use their solar electricity generation to offset their electricity consumption.  In other words, the customer's meter runs backwards for the amount of solar electricity produced by the solar system and added to the grid. Different states treat net metering differently. To learn whether net metering is available and how it works, a customer can check a state's incentive programs on the DSIRE website at

North American Board of Certified Energy Practitioners (NABCEP) Certification: NABCEP is the most respected and widely recognized solar PV certification organization for North American solar professionals. NABCEP was founded with the mission to develop and implement quality, industry-standard credentialing programs for solar companies and their installers. NABCEP’s certification programs are administered to the highest standards for testing and certification. The NABCEP PV Installation Professional Certifications have been accredited to the ISO/IEC 17024 standard by ANSI. Having our NABCEP-certified professionals overseeing your installation ensures you receive the highest quality installation in the industry.

Off-Grid: A stand-alone PV system, or off-grid system, is not connected to the utility company and draws on a bank of batteries for energy storage and usage.

Photon: A photon is an elementary particle of light. When a photon hits a solar panel, that initials the creation of solar energy.

(PV) Photovoltaic : A technology which converts sunlight into electricity.

Polycrystalline: A polycrystalline solar cell is a type of solar cell which is made from a block of silicon that has multiple crystals.

PPA: This is a Power Purchase Agreement. The array owner leases the land for a long term while earning money on their investment. They do this by selling the energy their array creates to the utility company. The land owner receives rental income from the array owner.

Racking: The supporting structure upon which solar modules are placed.

Solar Incentives: Financial incentives in the form of grants, tax credits and rebates to encourage the installation of solar PV systems.

Wafer: A thinly sliced silicon disc, used as the starting point for manufacturing a solar cell. 


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