Home Solar, Part 2: Definitions and Terms

2024-10-28

This blog post is the second in a series about installing solar panels on our house. In this post, we'll go over many of the definitions and terms that we came across, and try to define them in a way that's useful for someone that's not an electrician or solar installer.

Definitions

While we were planning our installation, we came across a lot of terms that and definitions, which we cover here to help you understand the rest of the series. We assume that you have a basic understanding of electrical terminology like AC vs. DC, volts, amps, watts, etc.

While many of the terms here are general and helpful when thinking about solar installations anywhere, some of them are specific to Ontario or Ottawa, where we live.

This post is pretty dense, and you don't need to read and understand all of it to get started with a solar installation. If you're just getting started, you can probably skip this post and refer back to it later. Feel free to jump ahead!

We're not electricians, and–despite having learned a lot during the course of this project–we're not experts in solar installations. This section is based on our understanding of the terms and concepts, and we're not responsible for any errors or omissions. If you're planning on installing a solar system, you should consult with a professional installer, electrician, and/or engineer.

If you notice anything that's incorrect or missing, please let us know so we can correct it.

Components and Hardware

Solar panels, sometimes called photovoltaic panels, or PV, are the components of the system that actually produce power. They have a variety of properties that are important when designing a system, and we'll cover more about them in a later post.
Optimizers/rapid shutdown devices are devices that attach to a solar panel (or are integrated into the panel) that are used when not using a microinverter-based system. Per code in Ontario, all solar systems must have a so-called "rapid shutdown", sometimes abbreviated RSD, that allows the system to be shut down in case of a fire or other emergency. Some RSDs also have the ability to optimize the power output at a per-panel level to reduce the impact of shade. Microinverters will provide rapid shutdown functionality when those are being used, and thus a separate device is not required.
Inverter is the component that converts the DC power produced by the solar panels (or batteries) into AC power that can be used by your house, or exported to the rest of the power grid.
- For inverters that support battery storage, they can typically also charge the battery by drawing AC power from the grid. These are sometimes called "inverter-chargers".
- There are two major types of inverters in use in residential installations today: microinverters vs. string inverters. We'll go into more detail in a later post, but broadly speaking, a microinverter is a small inverter that attaches to a single solar panel (or sometimes 2/4 panels), while a string inverter is a larger inverter that attaches to multiple panels that are connected in series in a "string".
Batteries are the component(s) that stores power for use later. There are a variety of battery chemistries in use today, and we'll cover more about them in a later post. Broadly speaking, though, there are two types of battery systems:
- AC-coupled batteries (like the Tesla Powerwall) are connected to other components of the system and the power grid via an AC connection, and integrate an inverter-charger into the battery itself.
- DC-coupled batteries (similar to a lead-acid or AGM battery that you'd find in your car) are connected to the rest of the system via a DC connection, and require a separate inverter to convert the DC power to AC power and vice-versa. So-called "all-in-one" inverters typically provide both the DC-AC conversion to connect solar panels and the DC-to-AC or AC-to-DC conversion for a connected battery.
Balance of system refers to all the other components of the system that aren't the solar panels, inverters, or batteries. This includes things like wiring, fuses, breakers, junction boxes, disconnects, and so on.
Lamacoids are the labels that are required to be placed on certain components of the system, to either provide information about the component or system (e.g. a copy of the SLD, described below) or to display a warning, such as "Two Power Sources" or "Rapid Shutdown Switch".

The word "lamacoid" is a trade name; the generic term for these is "nameplate", "legend plate", or "engraved plate". Typically, they are required to be weatherproof.

Parties

A Solar Installer is the company that installs the solar system. They're responsible for the design, permitting, installation, and commissioning of the system. They're also responsible for interfacing with the electrical utility and the Electrical Safety Authority (ESA) to get the necessary permits and inspections. They typically also provide a post-installation warranty and are responsible for any maintenance or troubleshooting that may be required.
Electrical Safety Authority (ESA) is the organization that is responsible for electrical safety in Ontario. They must be notified before any work is done, and will perform inspections and ensure that all electrical work is done to code.
The Electrical Utility is the company that provides power to your house. They're responsible for the power grid, billing, and are the final arbiter of whether a solar installation can be connected to the power grid, and how large of an installation is allowed. Sometimes referred to as the "power utility", "power company", "hydro company", etc. Here in Ottawa, this is Hydro Ottawa; elsewhere in Ontario it's typically Hydro One.

The phrase "supply authority" (e.g. as used by the ESA) can refer to the electrical utility as well, though it's more general than just the utility.
A Professional Engineer (abbreviated P.Eng.) is a person who is licensed to practice engineering in the province of Ontario. Note that this is different from someone that has a degree in engineering; a P.Eng. is a person who has passed the professional engineering exam and has been granted a license by Professional Engineers Ontario. Certain aspects of the solar installation must be designed and stamped by a professional engineer.
A Master Electrician is a person who is licensed to perform electrical work in the province of Ontario, by passing the master electrician exam administered by the ESA. They are responsible for the installation of the electrical components of the solar system, and are typically employed by the solar installer.
A Licensed Electrical Contractor is a company that is allowed to perform electrical work in the province of Ontario. They employ electricians to perform the work.

A professional engineer is very different from an electrician; an engineer is responsible for the design of the system, while an electrician is responsible for the installation. Unless a P.Eng. is also a licensed electrician, they cannot perform the installation themselves. Unless a licensed electrician is also a P.Eng., they cannot design a system that requires a P.Eng. stamp.

Planning, Design, and Permits

Single-line diagram (sometimes abbreviated as "SLD") is a diagram that shows the electrical connections between all the components of the system. This is a required document for the permit application and interconnection agreements with the electrical utility, and it's also a useful document to have when troubleshooting the system.
Permit, despite being a common term, is a bit of a misnomer in Ontario. To use the official terminology; you file a "notification of work" with the Electrical Safety Authority (ESA), where you specify the scope of the work that you're intending to do. The fees for these notifications are fairly complicated, but the ESA will walk you through the process on the phone. This is typically done by the solar installer.
Inspections are the process whereby an inspector from the ESA will come out to your house and inspect the work that was done. This is typically scheduled by the solar installer, and the inspector will check that the work was done to code and that it's safe. In Ontario, there are two kinds of inspections:
- Rough-in inspections are done before the system is energized, and checks that the wiring is done correctly, safety requirements are met, only approved components are used, etc. This inspection must be completed before the system is energized, and before any of the work completed is covered up (e.g. by drywall).
- Final inspections are done after the system is completed, and must performed before the electrical utility will grant permission to connect to and feed power back to the grid. Upon completion of the final inspection, the ESA will issue a Certificate of Inspection that the utility will require a copy of.
Connection Authorization is an approval from the ESA that the system is safe to connect to the power grid. This is typically required by the electrical utility before they will allow the system to be connected. The ESA will issue a "Connection Authorization Verification" certificate.
Distributed Energy Resources, often abbreviated "DER", is the term used by the electrical utility to refer to solar systems, battery storage, and other small-scale power generation systems. In Ontario, if your generation is a so-called "micro-generation" project, consisting of less than 10kW AC worth of generation capacity, then typically the utility will perform an abbreviated review of the system on a relatively short timeline and with minimal fees.

The electrical utility cares about the so-called "nameplate capacity" of any power generation, not what is theoretically possible in a given installation. So hypothetically, if you install a 20kW inverter, but only 8kW of solar panels, the utility will consider your system to be 20kW, and you'll be ineligible for the micro-generation program, even though your system is incapable of generating more than 8kW of power.

Connection Impact Assessment (often abbreviated "CIA") is the name of a form that must be filled out and submitted to the electrical utility. This form is used by the utility to determine if the proposed solar system will have any impact on the grid, and if there is capacity to support the proposed amount of power generation. This form is typically filled out by the solar installer, and is typically not required for micro-generation projects under 10kW AC of generation capacity.

Another name for this is a "Distribution Connection Impact Assessment" (abbreviated DCIA).

At least for Hydro Ottawa, the CIA application and drawings need to be stamped and signed by a professional engineer who is licensed in the province of Ontario and in good standing; this is a requirement regardless of who is performing the installation.

The timeline for a CIA can be quite long, especially if the utility has to perform a detailed review of the system, or if they're backlogged with applications. In our case, the CIA was submitted on October 6, 2022 and was approved on November 29, 2022, but we've heard anecdotal reports of the process taking many months.

An Electrical Operation and Maintenance Agreement (abbreviated EOMA) is a document that is signed by the homeowner and the electrical utility, that specifies the responsibilities of each. In our case (with Hydro Ottawa), this document specifies a collection of requirements, but more relevant to us, also include direct contact information for both the homeowner and the local system operator, in case either party needs to contact the other. While this hasn't come up so far from us, the agreement also states:

Each party’s Controlling Authority shall be available to each other on a 24/7 basis. Unavailability of the Customer’s Controlling Authority may result in Hydro Ottawa’s Controlling Authority disconnecting the DER.

— Hydro Ottawa EOMA

Generation Connection Agreement (GCA) is another agreement that we signed with Hydro Ottawa.

Other Terms

Distributed Generation is the generic term used to refer to power generators that are connected to a distribution system.
Home-Run is a term used to refer to a run of electrical cable that goes directly from a single component to a central location, rather than daisy chaining components together. This is typically used to refer to the wiring from the end of a string of solar panels back to the inverter; panels are typically connected such that the positives are all in series, positive-to-negative, and then the final ends are connected to the inverter.

Up Next

In the next part of this series, we'll cover how we found and chose our solar installer, and how we picked the specific components of our system. Stay tuned!