Common Solar Terminology

Overview

There's a lot of lingo thrown around in the solar industry, and it can be confusing for laypersons or experienced pros alike. Here's a few common things you might hear us refer to during your solar project. If you don't see the word you're looking for on this list, please suggest it to us!

Pro-tip: use "ctrl+f" to search for the word or abbreviation you're looking for to jump directly to it on the page

Term	Definition
AC	Alternating Current. The first part of AC/DC, this is the form of electricity your home uses. The inverter in your solar system takes DC electricity from your solar panels and changes it to AC for your home.
ACH	Automated Clearing House. Basically this means "paying cash" - this is an automatic billing or transfer to or from a bank account for electronic bill payments.
Adder	Any project cost that falls outside the standard project costs (solar & basic electrical) covered by the baseline.
AHJ	Authority-Having Jurisdiction. The city, county, or municipality that governs the properties in the homeowner's area, specifically when it comes to construction projects and acquiring building/electrical permits.
Array	Multiple solar panels connected to each other, sometimes used interchangeably with "system" but may also refer to a contiguous block of panels on a roof plane that are one part of the larger system.
Azimuth	The cardinal direction or point on the compass towards which each roof surface is facing. North is 0°, South is 180° (highest efficiency for solar), East is 90 and West is 270.
Baseline	The cost of completing a solar project, charged by ESP, measured in price per watt. Also known as a "redline". May or may not include certain adders based on project or territory.
Building Permit	Permission to install, received from the AHJ. In order for ESP to install solar, the plan sets require AHJ approval, which can take anywhere from instantaneous, a few days, to weeks or months, depending on the local municipal department and project specifics. We always want to provide transparent permitting timelines for areas where we have data in order to set proper expectations and create a great homeowner experience.
CARE Program	A program offered by some California utilities that provide reduced rates to low-income homeowners on their electric bills.
Cash Purchase	One of the methods a customer may choose to pay for the system. Always discuss with your customer what the best option will be for their situation - if someone has a lot of liquid capital and doesn't want to pay interest or lender fees, this is a great option for them. Note that this is generally via ACH or check, we don't expect homeowners to lug a huge briefcase of bills up to the office.
Change Order	Whenever a Project or Scope of Work changes significantly. Change Orders are used most often when major components or aspects need to change, such as the panel layout or the financed amount. Request a Change Order via our Live Chat or by calling Support.
Combiner Box	A small unit that combines cables/wires from an array of panels with microinverters, mounted on the roof underneath the array.
Conduit	A bright shiny tube that has electrical wires inside of it. Generally, this will connect an array to a string inverter on the exterior of a home. We always do our best to color-match the paint or shingle color when its visible.
Connection Fee	Utility billing terminology. A line item that represents the homeowners' ability to use a given utility's services (including their NEM program).
CPUC	California Public Utility Commission. The board that regulates rates and policy for all of the state’s utility companies, as well as net metering rules. (PG&E/ SDG&E/ SCE/ LADWP)
Credit Check	Inquiry from one or more credit bureaus that financing companies use to see if homeowners are worth lending to. Each finance company has different approval criteria. Some finance companies like Goodleap offer "low credit score" options to customers in the 600's but generally a 650 or higher is preferred to ensure a loan option is viable.
CRM	Customer Relationship Management. This is the software we use to manage all of the projects in our pipeline and all historic customer info. Our CRM is called QuickBase (QB) and Authorized Dealers get free access to this powerful tool.
DC	Direct Current. The second part of AC/DC, this is the form of electricity produced by your solar panels and how power capacity is measured.
Derate/D-Rate	When an electrician lowers the amperage from a breaker so the panel/breaker doesn't get maxed out and pull unsafe amounts of power. This is required to make the system safe to operate in some circumstances, and usually used to avoid a complete Main Panel Upgrade.
Dividend Finance	A solar loan provider partnered with ESP. Low dealer fees and great approval rates.
Duck Curve	Utility terminology. The "duck curve" represents the amount of power solar produces during the day as opposed to what the grid actually requires. Homes tend to use less power during the day while people are out and about (unless you work from home), and then fire up in the late afternoon and evening when people turn lights on, use appliances, etc. When graphed out over 24 hours it sort of looks like a rubber duckie if you squint a little (slightly higher in the morning, low at midday, and very high in the evening). This is partly why batteries are a huge opportunity and we encourage all sales teams to get Battery Certified as soon as possible.
Eave	Roof term. The lowest part of the roof, commonly where gutters are installed.
Electric Bill	A very important document! Every homeowner gets an electric bill reflecting the amount of power (kWh) they use each month. Required for interconnection and PTO. Refer to the Utility Bill FAQ's to see what areas you should focus on when sizing a system, and what is required for a Clean Contract/Perfect Packet submission on your newly submitted job.
Enphase	Global leader in microinverter manufacturing. Enphase microinverters carry a 25 year warranty and very long lifespans, and make it so every panel is "smart" and can operate independently from the rest of the system, producing and communicating on its own. They are more expensive but some homeowners prefer them for aesthetics and peace of mind.
Feet & Flashing	Part of the racking system that connects to the roof. This equipment comes in various styles but is always designed to prevent water from leaking into the roof.
Generation/Production	Generating or producing electricity. Depending on the context this can refer to the solar array producing clean electricity, or to utilities charging for their power plants generating electricity consumed by the homeowner (often paired with transmission charges).
GivePower	A charitable organization that develops clean water and electricity projects in rural or remote areas. They accomplish amazing things for people without access to basic human needs, and we're proud to donate a certain amount to their cause with every project we install.
GoodLeap	A solar loan provider partnered with ESP. Huge variety of options to fit the homeowner's situation.
Grid	Massive network of power plants, substations, wires and cables connecting our society. Homes are connected to the grid, even after solar installation, because of Net Metering (NEM). If there is a power failure, PV systems will automatically shut down so that repair workers don't get zapped - each PV system is a mini power plant! Going "off-grid" unfortunately isn't realistic for most people, but batteries are available if they want to protect themselves from grid uncertainty.
HIA	Homeowner Installation Agreement. Also known as the contract. Every homeowner will sign and receive the ESP HIA when you complete the sales process.
Hip	Roof term. Where two sections meet to form an angle, usually descending from the ridge down to the eave.
HOA	Home Owners Association. A board that places restrictions on the aesthetics or “look” of the homes in the neighborhood. Every HOA is different and some have very arduous processes and paperwork that delays going solar. Luckily California passed legislation long ago preventing HOA’s from having a significant impact on a homeowner's ability to go solar (sometimes called "solar right of way" laws). Many homeowners will want HOA approval prior to installation, but we also offer an HOA waiver in the event the homeowner wants to proceed and will deal with any HOA issues themselves.
Inspection	The AHJ sends an inspector to verify the work completion after install. The timeline can vary, but we coordinate a meeting time for a representative from our Install Team and a representative from the AHJ to assess the job and pass or fail based on the approved set of plans that we originally submitted to get the permit. The majority of our installations receive approval at the first inspection, but we will always communicate transparently on whatever it takes to fix what is needed until the inspection is approved and we can move to activation and completion.
Interconnection	The process of connecting the customer's solar system to the utility grid. In California, approval is granted by the utility after the passed inspection and is commonly referred to as Permission to Operate (PTO).
Inverter	Large device that converts DC into AC, referred to as a string inverter or central inverter. SolarEdge is our manufacturer of choice for inverters with optimizers.
Irradiance	Solar Irradiance is a measure of how much solar power a given location receives. California is one of the top 3 states in the country for solar irradiance. Actual solar potential varies throughout the seasons and even day-to-day depending on the weather.
ITC	Investment Tax Credit. This refers to the federal tax credit equivalent to 30% of the cost of the solar installation, including financing and some roofing projects. NEVER promise a customer they will get the tax credit. Homeowners are advised to consult with a tax professional. For more detail refer to the Solar 101 article about Credits & Incentives.
kW/kWh	Kilowatt(s) and kilowatt-hour(s). Forms of energy measurement. One kilowatt is one thousand watts. kW are used to "size" a system (ex. a 6.5 kW system or 6500 watts) while kWh are used to measure actual electricity consumed or produced (ex. your 6.5 kW system produced 1001 kWh last month and your home consumed 1000 kWh). Battery capacity is also measured in kWh.
LADWP	Los Angeles Department of Water and Power. A utility company that covers LA and the San Fernando Valley.
Lien	A legal property obligation. A lien is a claim for an asset or the value of an asset on the property, or for work done that must be paid before any other transaction related to the home can occur (such as refinance or sale).
Loan	One of the methods a customer may choose to pay for the system. After qualifying for a given loan option after a credit check, homeowners own their system and make fixed loan payments instead of their electric bill. Solar purchased via loan is eligibile for the federal ITC just like a cash purchase.
Microinverter	A small device attached underneath each panel that converts all of the energy from DC to AC for use in the home. Our microinverters are manufactured by Enphase and have a 25-year warranty, and cost a little more than SolarEdge inverters with optimizers but have many advantages. Discuss with the homeowner what makes the most sense for their home and roof orientation - microinverters are great when there are a lot of different roof planes pointing in different directions.
Mods	Modules, a.k.a. "glass" a.k.a. solar panels. Our base panel will always be a strong offering with high wattage and clean aesthetics
Monocrystalline	Solar cells manufactured from a single block (mono) of silicon into a wafer. These panels are more efficient and more attractive than the alternative manufacturing method of polycrystalline.
Mounting Plane	One section of the roof. Any time you cross over a hip, valley, or ridge, you're on a new plane of the roof. Solar arrays cannot cross mounting planes and must have conduit run between them or an individual combiner box for microinverters.
MPU	Main Panel Upgrade. May also be referred to as a Service Upgrade. This is the big electric panel that serves electricity to your home, and if you need an upgrade it's because your panel is an older model or doesn't have enough capacity for adding the solar system.
MSP	Main Service Panel. The primary electrical panel in a home that houses all the circuit breakers corresponding to various rooms and/or electrical appliances. If a panel does not have room for the solar breakers, or is outdated per building codes or too old and unsafe to hook more electrical circuits into, the project may require an upgrade (MPU).
Municipality	A town or city, a.k.a. an AHJ. Some municipalities have their own local utility company with different rules for net metering that can make solar a challenging proposition (Riverside Public Utility is an example).
NEM	Net Energy Metering (or just Net Metering). This is the agreement with the utility company allowing you to become a clean power plant and watch your meter spin backwards! We submit an application close to the start of every project to ensure activation after the inspection is as fast as possible.
NTP	Notice to Proceed. This means the financing company has approved and the project should move forward.
Offset	What percent of the homeowner's power the solar is expected to cover, as a percent. The offset represents what the PV system will produce in relation to the homeowner’s usage, based on either historical usage data or an estimate created for future anticipated needs. (e.g. they’re going to buy an electric vehicle, had a change in family size, or don’t have a year’s worth of historical data yet).
Optimizer	A small device attached under each panel, also called a Power Optimizer. These are manufactured by SolarEdge to be linked to the main inverter, and allow the system to continue functioning even if a single panel is not producing as much as the others, as well as letting our warranty & support teams pinpoint the problem to fix it.
Panels	Solar panels, a.k.a. solar electric or photovoltaic (PV) panels. Our base panel is the Aptos 440W as of the end of 2022. See also "Mods". Not to be confused with Main Service Panels.
Permitting	Permitting is the stage at which ESP submits a full building and electrical permit pack to an AHJ, either digitally or in-person, and then receives approval. Every AHJ is different in terms of turnaround time and requirements. Construction of any kind cannot commence on a home until the AHJ signs off. If there are redraws requested by the sales rep or homeowner after Design has been completed and Permit Submission started, it can cost thousands of dollars, time, energy, and resources.
PG&E	Pacific Gas and Electric, the major utility company for central and Northern California.
Pitch	Angle of the roof. Also referred to as “Tilt” or "Slope".
Plan Set / Permit Pack	An in-depth and thorough description of the PV system that will be installed for the homeowner. This is required by the town in order to approve the installation of the PV System. Different towns have different requirements for what is included in the Plan Set/Permit Pack. Requirements can range from how many panels, the kind of panel, where it will be drilled into the home, the kind of placards (warning signs) to be placed and where, and so on. This pack can be as many as 30 pages or longer.
Polycrystalline	Solar cells manufactured from a multiple fused blocks (poly) of silicon into a wafer. These have a blue “shattered” look and are generally less efficient in power production and less attractive on the roof. ESP does not install these on homes, as they are generally deployed for large-scale commercial applications, solar farms, etc. If your homeowner is worried about how the solar looks on the roof, make sure they aren't picturing these panels instead of the black-on-black mono panels.
Power Cycling	The act of restarting an installed solar inverter. This usually consists of shutting off the inverter, AC disconnects, and flipping breakers in the main service panel. Wait a few minutes and flip all the switches in reverse order to turn the stem back on. Our Warranty team will provide instructions to homeowners when needed for troubleshooting.
PPA	Power Purchase Agreement. One of the methods a customer may choose to acquire their solar system. Essentially the customer leases the system and pays the PPA company a fixed monthly cost with a minimal yearly escalator (percent increase). The PPA company maintains ownership of the system and so the customer is not eligible for the Solar ITC in this scenario. Sunrun is our current provider of PPA or "leased" systems.
PPW	Price per watt. This is a calculation of net or gross system cost, found by dividing the dollar amount charged by total number of watts in a solar system. For example, if a 3kW system costs $15,000 for the project, you take 15000 dollars/3000 watts to reach = $5.00/watt
PTO	Permission to Operate. Utility terminology. When the power company grants the homeowner's system permission to produce energy to be exported back to the grid and take advantage of NEM. PTO is not issued until after installation and a passed inspection and the PV System is not switched on, so customers won’t see savings on their energy bill until it is cleared to be a mini power plant of its own.
PV	Photovoltaic. Solar panels produce electricity by capturing sunlight and turning it into electricity through the photovoltaic effect. Photo = "light" + voltaic = "electricity".
Racking	The hardware that provides a support structure for the array. Panels will be bolted to the racking system, which is bolted to the roof. Also called mounting. Generally these are hardened aluminum rails fixed to the feet & flashing. Racking sits about 2-4 inches off the roof. This allows air circulation beneath the panels to avoid overheating of the system and the roof underneath.
Ridge	Roof term. The top of the house or peak of the roofline.
SCE	Southern California Edison. Large utility that covers most of Southern California outside of LADWP and SDG&E
SOW	Scope of Work. A summary of the project sold. The Scope of Work is intended to be the final checkpoint to change project details prior to moving toward installation.
SDG&E	San Diego Gas and Electric. Medium-sized utility that covers southern Orange County and San Diego
Sealant	Special waterproof goo. Installers apply sealant with a caulking gun at the point of every roof penetration to prevent leakage issues as the system and roof around it ages.
Site Survey	Once all of the paperwork has been completed and the project has been submitted, a site audit is scheduled where a technician will visit the home to finalize the placement of the equipment to be used in the project (panels, inverter, conduit, etc.). This stage is also where it will be determined if there are any changes to be made to the project.
Smart Meter	Utility company equipment for tracking kWh. Smart meters were installed on all California homes starting around 2009-2010 and allow meters to be read remotely and also allow for Net Metering. These were made so that people can go solar because it tracks the production and consumption of power in both directions (power in from the grid/power out to the grid from the PV System).
Solar Access	Solar access measures how much sun your roof will get based on shading from nearby trees or buildings. Solar Access is expressed as a percentage of your roof with ideal shading conditions, i.e. no shade at all.
Solar Panels	A series of silicon wafers (or “cells”) connected by conductive metals that create an electrical charge when exposed to UV rays. Otherwise known as photovoltaic panels.
SolarEdge	Currently the best residential inverter manufacturer in the industry. SolarEdge makes a very safe inverter with multiple kill switches that can be remotely activated or deactivated. We offer a variety of other SolarEdge products including Battery Backup systems.
SOLO	Software tool used for entering leads, requesting proposals, and signing documents. SOLO charges per proposal generated, which is invoiced monthly. If you maintain a certain number of sales and close rate every month we will cover the fees charged.
SSA	Solar Service Agreement. Also known as the homeowner agreement or contract.
Storage	Home battery system. Allows the homeowner to save the power they produce for later use in their own home ("behind the meter") rather than exporting to the grid through a NEM program. Energy storage has been around for a long time, and is growing in popularity for homes around the world. Our current battery option is Solaredge - sign up to take the Battery training on our page ASAP!
Sunrun	A large installation and finance company. ESP leverages Sunrun's third-party ownership finance products including leases and PPA’s.
SV	Site Visit. Also called Site Survey (SS), Site Audit (SA), or Site Inspection (SI). This is the initial site survey to figure out where panels will go and other details about the property and project. Once a salesperson submits a signed contract with all other required paperwork, they reach out to the ESP Support team for us to schedule a technician. We send confirmation to the homeowner and make sure they are either at home or leave access to critical areas unlocked so we can conduct a thorough inspection. Not to be confused with a Final Inspection after the solar is installed.
System	Multiple solar panels connected to each other along with an inverter/microinverters to form a complete solar energy system.
System Activation	The final stage of the solar installation process is when ESP activates the customer's solar system. They receive a monitoring portal link and start running on sunshine!
Tiers	Utility billing terminology. Most utilities use a tiered billing system where they charge more per kWh for the increased power being used or for different times of day (TOU). Each utility provider has a set of different tiers and prices associated with each tier.
TOU	Time Of Use. Utility billing terminology. Customers are charged based on the time of day power is being used, how hot the demand for power is at that time across the grid, and how much power is available to be distributed. Everyone in California will soon be switched to TOU. All who go solar will automatically be enrolled in TOU and will get credits for producing energy that is not used by the home and given back to the grid for other homes to use.
TOF	Tilt and Orientation Factor. TOF measures how much sun your roof will get based on its tilt and orientation. TOF is expressed as a percentage of a roof with ideal tilt and orientation.
Transmission	Utility terminology. Transmission is the act of moving power from the transformer at the power plant to the transformer or substation in the neighborhood of the homeowner. Transmission lines are extensive and can run for hundreds of miles, and this is where utilities make a lot of their profits by constructing new transmission lines or other projects where they are guaranteed a percent of the profits, instead of being held liable for maintaining older equipment.
Trenching	Digging a long ditch to lay down electrical conduit, generally when the array is on a ground mount or on a structure far away from the main electrical panel of the home.
TSRF	Total Solar Resource Fraction. TSRF accounts for tilt, orientation, shade and Solar Access. It is the most accurate and comprehensive of the methods to calculate any roof’s solar-friendliness, and lets us make precise representations of how much solar a given roof can convert into electricity, so ESP incorporates this into our Design process on every job using proprietary software and processes.
UCC-1	Uniform Commercial Code. A UCC-1 filing is different from a normal lien, and means that the company that owns the system has fixture filing (a claim attached to the home) on the deed of the property. If and when the homeowner wishes to refinance or sell the home, the UCC-1 must be lifted (removing the filing of the fixture from the deed until the refinancing or sale is done). This applies to both the Solar Loan and the PPA.
Valley	Roof term. Where two sections of roof meet and form a valley or trough (the opposite of a hip).