Home Solar Glossary

Curious about solar terms like net metering, battery capacity, or inverter? Use this glossary to get clear, simple definitions for the most common solar energy concepts.

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A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

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A

Azimuth

• Definition: The compass direction that solar panels face, measured in degrees from true north (0°/360°), with south being 180°. For homeowners, it’s important because the azimuth determines how much direct sunlight panels receive, directly affecting energy production and efficiency.
• How you might hear it: Your panels will be facing directly south, so the azimuth is 180 degrees.
• Related Terms: Solar Access 
• Relevant Blog Post(s): SmartRoof Best Practices and Tips, Solar panels for flat roofs: is it worth it?

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B

Backup

• Definition: Having stored or alternative electricity available when the grid goes out or when your solar panels aren’t producing enough power (like at night or during a storm). This usually comes from a battery system (such as a Tesla Powerwall) or sometimes from a backup generator.
• How you might hear it: We added backup to our solar system, so even during last summer’s outage, our home stayed powered.
• Related Terms: Battery Capacity, Battery Storage, TOU, Net Metering
• Relevant Blog Post(s): Solar energy storage: everything you need to know, Are solar batteries worth the cost?

Battery Capacity

• Definition: The total amount of electricity a solar battery can store, measured in kilowatt-hours (kWh). 
• How you might hear it: The more battery capacity you have, the longer the battery can run your home during an outage.
• Related Terms: Battery Storage, Kilowatt, Kilowatt-Hour
• Relevant Blog Post(s): Are solar batteries worth the cost?, Adding battery storage to your design

Battery Storage

• Definition: Often referred to as a “home battery,” “battery backup,” or simply a “battery”, battery storage is a device that stores excess electricity generated by solar panels for later use. It allows homeowners to use stored energy at night, during cloudy periods, or during power outages, reducing reliance on the grid and improving energy independence. Batteries can also store energy to sell back to the grid when export rates are high.
• How you might hear it: This system includes battery storage, so if the power goes out, your fridge, lights, and Wi-Fi will keep running.
• Related Terms: Battery Capacity, Backup
• Relevant Blog Post(s): Are solar batteries worth the cost?, Turn your home into a smart asset 

BOS (Balance of System)

• Definition: Everything in a solar system except the solar panels. This includes inverters, racking, wiring, switches, and safety equipment. 
• How you might hear it: The panels are what you see on the roof, but the balance of system — things like inverters, wiring, and mounting hardware — is what makes sure the power actually flows to your house
• Related Terms: Inverter, Ground Mount Systems, Racking/Mounting

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C

Change Order

• Definition: A revision to the original solar contract, often due to unforeseen site issues or system design changes.
• How you might hear it: We’ll need a change order to move some panels because we didn’t use an accurate shade analysis tool.
• Relevant Blog Post(s): Changing change orders: tackling solar’s dirty little secret

Community Solar

• Definition: Community solar programs let you subscribe to a local solar facility to get the benefits of solar without having a solar panel system on your property.
• How you might hear it: If your roof isn’t a good fit for panels, you can join a community solar program and still save on your monthly bill.
• Related Terms: Net Metering, SRECs
• Relevant Blog Post(s): Community solar 101, Are “free solar panels” really free? , What you need to know about net metering 

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D

Derate Factor

• Definition: An estimate of how much real-world conditions (like shading and temperature) reduce a system’s output. Solar panels are tested under specific lab conditions, but in real life, things like wiring, the inverter, temperature, and even dust can cause small losses. So, instead of getting 100% of the panel’s rated power, you usually get a bit less. The derate factor accounts for those real-world conditions, giving you a more realistic picture of how much energy your system will actually produce.
• How you might hear it: Your system is rated for 6 kilowatts, but after applying the derate factor, we expect about 5.5 kilowatts of usable power under normal conditions.
• Relevant Blog Post(s): How does a photovoltaic (PV) system produce electricity?

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E

Energy Payback Period

• Definition: The amount of time it takes for a solar system to generate the same amount of energy that was used to manufacture, transport, and install it. After this period, the system produces net-positive renewable energy for the rest of its lifespan.
• How you might hear it: The energy payback period for most solar panels is just a few years, but the panels will keep producing clean power for 25 years or more.
• Relevant Blog Post(s): Quantifying the value of a solar installation: some helpful metrics

Export Rates

• Definition: The payments or credits homeowners receive from their utility for excess solar electricity sent to the grid. These rates are often tied to programs like net metering or time-of-use (TOU) billing, where the value of exported energy can change depending on when it’s sent back. Utilities or state regulators typically set the rates, which may be flat (a fixed value for each kilowatt-hour), TOU-based (higher during peak demand hours and lower off-peak), or dynamic (adjusting in real time with grid conditions).
• How you might hear it: Your utility’s export rate is 8 cents per kilowatt-hour, so that’s what you’ll earn for the extra solar energy you send back to the grid.
• Related Terms: Net Metering, TOU
• Relevant Blog Post(s): Understanding time-of-use rates: a guide for homeowners – Home Solar Blog, What you need to know about net metering – Home Solar Blog, Are solar batteries worth the cost?  – Home Solar Blog

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G

Grid-Tied Solar Systems

• Definition: The vast majority of residential solar systems are grid tied. It just means that the system and your home are connected to the power grid. Your house runs on solar energy when the sun is shining, and relies on energy from the grid for any extra power needs (at night, when you’re using more energy than the panels produce, etc.) These systems can send power back to the grid for net metering.
• How you might hear it: This is a grid-tied solar system, so you’ll get electricity from the utility when your panels aren’t producing as much electricity as you’re using.
• Relevant Blog Post(s): How do solar panels work? Everything you need to know

Ground Mount Systems

• Definition: A solar panel system that’s installed onto a racking system on the ground instead of on a roof.
• How you might hear it: If you have a lot of land that gets direct sunlight, a ground mount system can be a good option.
• Related Terms: Racking/Mounting

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I

Interconnection

• Definition: The process of connecting your solar system to the utility grid. It’s the step that lets your solar panels not only power your home but also send extra electricity back to the grid (and earn you credits or payments). Without interconnection, your solar system can’t legally operate or share power with the utility.
• How you might hear it: Our system was installed last month, but we had to wait for the utility to approve the interconnection before we could start using it.
• Related Terms: Grid-Tied Solar Systems

Inverter

• Definition: The device (or devices) in a solar system that converts direct current (DC) electricity from solar panels into alternating current (AC), which is the type of electricity homes and appliances use. It acts as the bridge between solar panels, batteries, and household power needs. 
• How you might hear it: Your system will have a central inverter that converts the solar energy into usable power for your home.
• Related Terms: Grid-Tied Solar Systems, Microinverter, String Inverter
• Relevant Blog Post(s): Solar inverter sizing: Choose the right size inverter, Are solar batteries worth the cost?

ITC (Investment Tax Credit)

• Definition: A federal tax credit for installing solar, currently 30% for residential systems in the U.S. This program is ending as of Dec. 31, 2025. To qualify for the credit, systems have to be installed and operational by the deadline. The 30% tax credit can be applied to your upcoming federal income taxes based on the cost of the new, qualified system and installation costs.
• How you might hear it: With the 30% federal Investment Tax Credit, you’ll get nearly a third of your system cost back as a credit on your next tax return.
• Related Terms: SREC (Solar Renewable Energy Credit)
• Relevant Blog Post(s): What to Know About the Solar ITC Step Down, Why now is the best time to go solar: What recent policy changes mean for you, How do federal solar tax credits work?

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K

Kilowatt (kW)

• Definition: A unit of power that measures how much electricity something can produce or use at one moment in time. 1 kW is equal to 1,000 watts. For example, a central air conditioning unit may use 3,000 to 5,000 watts, or 3-5 kW. Solar systems are measured in kW.
• How you might hear it: Your home will need about a 7-kilowatt solar system to cover most of your annual electricity use.
• Related Terms: Battery Capacity, Kilowatt-Hour, Watt-hour
• Relevant Blog Post(s): Solar Fundamentals: Making Sense of Kilowatts and Kilowatt Hours

Kilowatt-hour (kWh)

• Definition: A unit of energy. It represents the amount of energy used over time (1 kW of power for 1 hour).
• How you might hear it: Your system is expected to generate about 9,000 kilowatt-hours of electricity per year, which should cover most of your usage.
• Related Terms: Battery Capacity, Kilowatt, Watt-hour 
• Relevant Blog Post(s): How to size a PV system from an electricity bill, kW vs. kWh: Watts, kilowatts, and kilowatt-hours explained

Leased System / “Solar Lease”

• Definition: The homeowner pays a fixed monthly fee to “rent” the solar system instead of owning it. The third-party financier pays for installation and upkeep of the system. The panels still produce electricity for your home, which lowers your utility bill, but you don’t own the system — the company does.
• How you might hear it: With a solar lease, you won’t pay anything upfront — just a fixed monthly fee for the panels, and you’ll still save on your electric bill.
• Related Terms: Solar-as-a-Service/PPA (Power Purchase Agreement)
• Relevant Blog Post(s): Are “free solar panels” really free?

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M

Microinverter

• Definition: A small device attached to each individual solar panel. Its main job is to convert the direct current (DC) electricity produced by a solar panel into alternating current (AC) electricity, which is the type of power used in homes. Unlike traditional string inverters, which connect and manage multiple panels together, microinverters allow each panel to operate independently.
• How you might hear it: We recommended using microinverters since different parts of your roof get shade at different times. 
• Related Terms: Inverter, String Inverter
• Relevant Blog Post(s): Solar inverter sizing: Choose the right size inverter

Monocrystalline

• Definition: A type of silicon photovoltaic cell used in solar panels that is made from a single-crystal silicon structure. These are generally the most efficient solar cells for residential solar. They are black and sleek-looking. 
• How you might hear it: We recommend monocrystalline panels for your home because they’ll generate more power per square foot and look uniform on your roof.
• Related Terms: Photovoltaic, Polycrystalline, Thin-Film, PERC
• Relevant Blog Post(s):  How big are solar panels?, How long do solar panels last?

MPPT (Maximum Power Point Tracking)

• Definition: Maximum Power Point Tracking (MPPT) is a technology used in solar inverters and charge controllers to maximize the energy captured from solar panels. It continuously adjusts the electrical operating point of the panels to find the “sweet spot” where voltage and current combine to deliver the most power. By doing this, MPPT improves efficiency and ensures you get the highest possible energy yield from your solar system, even as sunlight conditions change.
• How you might hear it: Even when a few panels are partly shaded, the MPPT keeps the system running efficiently.
• Related Terms: Inverter 
• Relevant Blog Post(s): MPPT – Everything You Need to Know About Maximum Power Point Tracking

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N

Net Metering (NEM)

• Definition: Net metering is a billing system that allows homeowners with solar panels to earn credit for the excess electricity they send to the grid. When solar production is higher than home usage, the meter “spins backward,” and those credits offset electricity drawn from the grid at other times. (In modern systems, the digital meter just shows electricity flowing from the home to the grid.) Utilities or state regulators set the rules, which may use one-to-one retail credits, reduced export rates, or time-of-use (TOU) structures depending on local policy.
• How you might hear it: With net metering, the extra power your system produces during the day offsets what you use from the grid at night, lowering your overall bill.
• Related Terms: TOU
• Relevant Blog Post(s): What you need to know about net metering

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O

Off-Grid System

• Definition: A solar panel system that operates independently of the utility grid. Off-grid households cannot use public energy utilities if their solar power is insufficient. Off-grid homes use battery storage, or they have a propane tank on the property or other back-up generator.
• How you might hear it: Because your remote cabin isn’t connected to the utility, you’ll need an off-grid solar system with batteries to power everything year-round.
• Related Terms: Grid-Tied Solar Systems

Offset

• Definition: The percentage of a homeowner’s electricity usage that a solar system covers. (So, “100% offset” = covers all usage). Offset can exceed 100% if a system is oversized, though utilities may cap it. 
• How you might hear it: Based on your roof size, this system will give you about a 75% offset, which means three-quarters of your annual electricity use will come from solar.

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P

PACE Loan (Property-Assessed Clean Energy)

• Definition: A type of solar panel system financing that applies the amount owed to a homeowner’s property tax bill rather than a separate bill. PACE programs are now active in 32 states plus Washington, D.C. 
• How you might hear it: With a PACE loan, you don’t need money upfront — the cost is added to your property taxes and spread out over many years.
• Relevant Blog Post(s): Your Solar Finance Primer: What to Know About the Top Four Solar Financing Options

PERC (Passivated Emitter and Rear Cell)

• Definition: A solar cell technology that can be applied to both mono and poly panels. PERC adds a special layer on the back of the cell that reflects light for another pass, capturing energy that would otherwise be lost and boosting efficiency.
• How you might hear it: We recommend PERC panels because they’re more efficient, so you’ll get more electricity out of the space you have on your roof.
• Related Terms: Photovoltaic, Monocrystalline, Polycrystalline
• Relevant Blog Post(s): What you need to know about PERC solar cells, How long do solar panels last?, How big are solar panels? 

Permitting Hell

• Definition: Frustration around slow or complex permitting processes, often at the city level.
• How you might hear it: The installation only took a couple of days, but permitting hell added two extra months before we could finally turn the system on.

Polycrystalline

• Definition: A type of silicon photovoltaic cell used in solar panels that is made of multiple silicon crystals that are melted together. They usually have a bluish color and are a bit less efficient than monocrystalline panels.
• How you might hear it: Polycrystalline panels are a good choice if you want to save on upfront costs and you have enough roof space to install a larger system.
• Related Terms: Monocrystalline, Photovoltaic
• Relevant Blog Post(s) How long do solar panels last?

Power Purchase Agreement (PPA) / Solar-as-a-service

• Definition: A contract agreement where a third party owns the solar system, and the homeowner buys a certain amount of power it produces at a certain price (usually at a discount).
• How you might hear it: With a PPA, you’ll pay for the solar energy your system produces at a discounted rate, but you won’t have to cover installation costs.
• Related Terms: Leased System / “Solar Lease”
• Relevant Blog Post(s): Are “free solar panels” really free?

Power Rating (Watts or kW)

• Definition: The maximum power output a solar panel can deliver under standard test conditions (STC). This means that, for example, a panel with a power rating of 400 watts can generate up to 400 watts of electricity under specific testing conditions. Right now, most residential solar panels are between 400 and 500 watts. 
• How you might hear it: These panels have a power rating of 425 watts, so we’ll need fewer of them to meet your energy needs.
• Related Terms: Kilowatt
• Relevant Blog Post(s): Understand solar panel specification sheets and how to read them

PUC / PSC (Public Utilities Commission / Public Service Commission)

• Definition: State-level regulatory bodies that oversee utilities and solar programs. In the context of residential solar, the PUC decides policies like net metering, export rates, interconnection requirements, and time-of-use pricing, which directly affect the value of rooftop solar for homeowners.
• How you might hear it: The PUC recently updated the net metering rules, so homeowners will still get full credit for the excess energy they send to the grid.

PV (Photovoltaic)

• Definition: A technology that converts sunlight into electricity using semiconducting materials in a solar PV system. Solar panels are often called photovoltaic panels or PV panels because they use special materials (like silicon) that create electricity when sunlight hits them.
• How you might hear it: Your home will have a 6-kilowatt photovoltaic system, which means solar panels that generate electricity from sunlight.
• Related Terms: Monocrystalline, Polycrystalline

PV Monitoring

• Definition: The system or software that lets you track how much electricity your solar panels are producing. Monitoring (usually through a mobile app or web portal) helps confirm the system is working correctly, shows energy savings over time, and alerts you to performance issues like shading or inverter faults.
• How you might hear it: Your system comes with PV monitoring, so you can log into an app to see your solar production anytime.
• Related Terms: Photovoltaic, Power Rating (Watts or kW)

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R

Racking / Mounting

• Definition: The hardware that secures solar panels to a building or the ground. It makes sure the panels are angled correctly toward the sun, can handle wind, rain, and snow, and stay safe for the lifetime of the system.
• How you might hear it: We’ll use a flush-mount racking system so your panels sit close to your roof for a clean look.
• Related Terms: Ground-Mount Systems
• Relevant Blog Post(s): Solar panels for flat roofs: is it worth it?

Renewable Portfolio Standard (RPS)

• Definition: A state policy that requires utilities to get a certain percentage of their electricity from renewable sources like solar, wind, or hydro. In the context of home solar, RPS programs often encourage utilities to support rooftop solar through incentives, rebates, or favorable net metering rules, since homeowner-generated solar power helps the utility meet its renewable energy targets.
• How you might hear it: Because of our state’s Renewable Portfolio Standard, the utility is required to get 30% of its power from clean energy, which is why they offer good solar credits.
• Related Terms: PUC / PSC (Public Utilities Commission / Public Service Commission)

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S

SGIP (Self-Generation Incentive Program)

• Definition: A California initiative that provides financial incentives for homeowners who install battery storage alongside their solar systems. It helps reduce upfront costs, making solar-plus-storage more affordable while also supporting grid reliability and backup power during outages.
• How you might hear it: If you add a battery, you can apply for SGIP rebates, which could cover a big part of the cost.
• Related Terms: Net Metering
• Relevant Blog Post(s): California Solar Storage Incentives For 2022 and Beyond

Site Survey

• Definition: A technician’s visit to assess a home’s suitability for solar (roof condition, shading, electrical setup, etc.).
• How you might hear it: The site survey only took about an hour — they inspected the roof and attic to make sure everything was good for solar.

Soft Costs

• Definition: Non-hardware costs like permitting, customer acquisition, inspection, and financing. They don’t generate electricity, but they’re a big part of the total price of a solar system — often making up more than half of the overall cost.
• How you might hear it: Even though panels are getting cheaper, soft costs like permitting and labor still make up a big part of the project price.
• Relevant Blog Post(s): What are solar soft costs? An industry overview

Solar Access

• Definition: Solar access has two main uses when it comes to residential solar. First, it’s the right of a homeowner to have access to direct sunlight so their solar panel system can work properly, regardless of HOA rules. Solar access laws vary based on state and location. Second, in solar design, solar access is a way of accounting for shading on a solar system. A site with very few trees and shading generally has good solar access.
• How you might hear it: Because of solar access laws in this state, your HOA can’t stop you from putting panels on your roof.
• Related Terms: Tracker / Tracking Collector

Solar Renewable Energy Credit (SREC)

• Definition: A solar program where you can earn money for each 1,000 kWh your system produces, which can be sold to utilities to meet the utility’s renewable requirements.
• How you might hear it: In addition to bill savings, your system will generate SRECs that you can sell for extra income.
• Related Terms: Net Metering
• Relevant Blog Post(s): How do I calculate SRECs?

String Inverter

• Definition: A device that connects a group (or “string”) of solar panels together and converts the direct current (DC) electricity they generate into alternating current (AC) electricity used in your home. Instead of each panel having its own inverter, all the panels in the string feed into one central inverter.
• How you might hear it: This system uses a string inverter, so all the panels are connected together. 
• Related Terms: Inverter, Microinverter
• Relevant Blog Post(s): Solar inverter sizing: Choose the right size inverter

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T

Thin-film

• Definition: A type of lightweight solar panel that uses a thin, flexible layer of photovoltaic material to collect sunlight. These panels have a lower efficiency than other types, and are rarely used in residential solar.  
• How you might hear it: Thin film panels aren’t as efficient as crystalline ones, right now their main uses are in commercial and utility-scale solar installations.
• Related Terms: Photovoltaic, Monocrystalline, Polycrystalline 
• Relevant Blog Post(s): How long do solar panels last? 

Time-of-Use (TOU) Rates

• Definition: Utility pricing plans where the cost of power changes depending on the time of day, day of the week, month, or season.
• How you might hear it: Since your utility has time-of-use rates, adding a battery will help you avoid paying high prices during peak evening hours.
• Relevant Blog Post(s): Understanding time-of-use rates: a guide for homeowners,   What are peak and off-peak hours for electricity? 

Tracker / Tracking Collector

• Definition: A mounting device that automatically moves a solar panel in the direction of the sun so it continues receiving direct sunlight when possible. 
• How you might hear it: Ground-mounted panels with a single-axis tracker can boost your energy production compared to fixed panels.
• Related Terms: Solar Access, Ground Mount Systems, Racking / Mounting

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W

Watt (W)

• Definition: A unit of power that shows how quickly energy is being generated or used — the more watts, the more quickly it’s happening.
• How you might hear it: These 450-watt panels are slightly more expensive, but they’ll generate more power than the 400-watt ones.
• Related Terms: Kilowatt, Kilowatt-Hour
• Relevant Blog Post(s): How many watts does it take to run a house?

Watt-hour (Wh)

• Definition: The unit of energy equal to one watt of power for one hour.
• How you might hear it: Your panels will produce about 30,000 watt-hours of energy per day, which equals 30 kilowatt-hours.
• Related Terms: Kilowatt, Kilowatt-Hour
• Relevant Blog Post(s): How many watts does an air conditioner use?