Glossary
Solar energy comes with its own vocabulary. This glossary defines the most common terms you'll encounter when researching residential solar in Ontario.
Use this as a reference whenever you come across an unfamiliar term in the Resource Hub or in a solar quote.
A
AC (Alternating Current)
The type of electricity used in your home and by the grid. Solar panels produce DC electricity, which must be converted to AC by an inverter before it can be used in your home.
AC Size Limit (10 kW AC)
In Ontario, residential solar systems are limited to 10 kW of AC inverter capacity. This is a regulatory limit, not a technology limit.
B
Battery Storage
A system that stores solar electricity for later use, typically during power outages. Batteries are optional and are not required for net-metered solar systems.
C
Cost per Watt ($/W)
This is the unit cost of a solar panel installation. It is calculated by dividing the total system cost by the system size in watts and allows for fair comparison between quotes.
Clipping
Occurs when solar panels are capable of producing more power than the inverter can convert. Excess production is "clipped" during peak sunlight hours. This is normal in many system designs.
Cash Flow
The difference between hydro bill savings and any loan or financing payments associated with a solar system.
D
DC (Direct Current)
The type of electricity produced by solar panels. DC power only flows in one direction and must be converted to AC by an inverter.
DC-to-AC Ratio
The ratio between the solar panel array size (DC) and the inverter size (AC). Ratios up to 2:1 are possible but some clipping will occur.
Depth of Discharge (DoD)
The percentage of a battery's capacity that can be used. Higher DoD generally allows more usable energy from a battery.
Degradation Rate
The gradual reduction in a solar panel's output over time, typically around 0.5% per year.
E
ESA (Electrical Safety Authority)
The authority responsible for electrical inspections and approvals in Ontario.
ESA Inspection
An electrical inspection performed by the Electrical Safety Authority to ensure the system complies with the Canadian Electrical Code.
G
Grid-tied
A solar system that is connected to the electrical grid. This allows excess electricity to be exported to the grid in exchange for hydro bill credits through net metering. When solar production is low, the home can also draw electricity from the grid as needed.
H
Hydro Interconnection
The approval process required to connect a solar system to the electrical grid including permits, technical review and authorization from the local hydro company.
I
Inverter
A device that converts DC electricity from solar panels into AC electricity for use in your home or export to the grid. Every grid-connected solar system requires an inverter.
Islanding (Anti-Islanding)
A safety feature that automatically shuts down a grid-tied solar system during a power outage to protect hydro workers.
K
Kilowatt (kW)
A unit of power that describes the size of a solar system. System size is calculated by adding up the wattage of each panel and converting to kilowatts.
Kilowatt-hour (kWh)
A unit of energy that measures how much electricity is produced or consumed over time. This is what you see on your hydro bill or inverter monitoring app.
Kilowatt-peak (kWp)
A measure of a solar system's maximum power output under ideal conditions, such as clear skies and strong sunlight. It's used to describe the rated capacity of solar panels and systems, not what they produce at all times.
L
Load Displacement
A solar system configuration where any excess power sent to the grid does not receive hydro bill credits. Because exported electricity provides no financial benefit, these systems often include battery storage to capture surplus energy for later use rather than sending it to the grid without compensation.
Levelized Cost of Energy (LCOE)
A long-term average cost per unit of electricity produced by a solar system over its lifetime accounting for installation cost and electricity production.
M
Microinverter
A small inverter installed behind each individual panel mounted to the racking. Microinverters are always mounted outside.
Manufacturer Warranty
A warranty provided by the equipment manufacturer covering panels, inverters or batteries regardless of installer status.
Modules
Individual solar panels that convert sunlight into electricity. A solar array is made up of multiple modules wired together.
MPPT (Maximum Power Point Tracking)
A feature in modern inverters that continuously adjusts the system to operate at the optimal voltage and current, maximizing energy production as sunlight conditions change.
N
Net Metering
A solar system configuration that allows excess solar electricity to be sent to the grid in exchange for hydro bill credits. These credits can then be used to offset future electricity imports. In Ontario, unused credits expire after 12 months.
O
Optimizer
A device installed at each panel that improves performance and monitoring while still using a string inverter. Allows a string inverter system to operate similarly to a microinverter system.
Off-grid
A solar system that is not connected to the electrical grid. Off-grid systems rely on batteries and often a backup generator and are typically used in remote or seasonal properties.
P
Photovoltaic (PV)
The technology used by solar panels to convert sunlight directly into electricity. Residential solar systems are often referred to as solar PV systems.
Payback Period
The length of time it takes for hydro bill savings to equal the upfront cost of a solar system.
S
String Inverter
A string inverter is a centralized inverter that converts electricity from multiple solar panels wired together in a "string" into usable AC power. String inverters can be installed either outside or inside a home.
Solar Potential (kWh per kW)
A metric used to describe the efficiency of a solar system. It represents how many kilowatt-hours a system produces annually for each kilowatt of installed capacity.
System Offset (%)
The percentage of a home's annual electricity use that a solar system is designed to produce. A 100% offset means annual production equals annual consumption, but many systems are intentionally sized below this level.
Solar Array
The complete group of solar panels (modules) installed together on a roof or ground-mount that work as a single system to generate electricity.
Solar Panel
A device made up of photovoltaic cells that converts sunlight into DC electricity. Solar panels are also referred to as modules.
W
Workmanship Warranty
A warranty provided by the installer that covers installation-related issues such as roof leaks or wiring problems.
