Understanding Solar Panels

A solar arrayThe complete group of solar panels (modules) installed together on a roof or ground-mount that work as a single system to generate electricity. is a group of solar panels installed together to generate electricity. On most homes, the array is mounted on the roof, but panels can also be installed on the ground when roof space is limited or unsuitable. Each solar panelA device made up of photovoltaic cells that converts sunlight into DC electricity. Solar panels are also referred to as modules. contains 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. cells that convert sunlight into direct current (DCThe type of electricity produced by solar panels. DC power only flows in one direction and must be converted to AC by an inverter.) electricity through the photovoltaicThe technology used by solar panels to convert sunlight directly into electricity. Residential solar systems are often referred to as solar PV systems. effect.

Because homes use alternating current (ACThe 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.) electricity, an inverterA 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. is required to convert the direct current (DCThe type of electricity produced by solar panels. DC power only flows in one direction and must be converted to AC by an inverter.) electricity produced by solar panels into usable power. Inverters also perform several important functions, including fault protections, energy production monitoring and maximum power point tracking (MPPTA feature in modern inverters that continuously adjusts the system to operate at the optimal voltage and current, maximizing energy production as sunlight conditions change.) to maximize system output. There are three main types of inverterA 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. systems used in residential solar:

• String inverterA 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.: A single inverterA 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. converts DCThe type of electricity produced by solar panels. DC power only flows in one direction and must be converted to AC by an inverter. electricity from strings of solar panels into ACThe 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. electricity. String inverters are the original solar inverterA 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. technology and are considered to be a robust option more commonly used in low-shading situations.
• String inverterA 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. with optimizers: Instead of strings of solar panels feeding a single inverterA 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. directly, the solar panels have optimizers installed underneath them which provide MPPTA feature in modern inverters that continuously adjusts the system to operate at the optimal voltage and current, maximizing energy production as sunlight conditions change. and control the voltage fed to the inverterA 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.. An optimized system is most often used in a situation where there is shading, as the individual optimizers mitigate its effects.
• Microinverters: Multiple inverters are installed under the solar panels, converting DCThe type of electricity produced by solar panels. DC power only flows in one direction and must be converted to AC by an inverter. to ACThe 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. at the panel level. Microinverters are well suited to residential systems and have become increasingly popular in recent years due to their flexibility and strong performance on complex or partially shaded roofs.

Your inverterA 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. will come with a monitoring portal which you can access though your internet browser or through a smartphone app. Through the portal or app, you can track the performance of your solar system by viewing your daily electricity production, monitoring monthly trends and identifying potential issues such as underperforming panels or inverterA 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. faults. We recommend checking the app weekly at first to establish a sense of normal system behaviour and then regularly in the spring and summer. If there is snow on your solar panels you may see errors, but don't worry they should go away as soon as the snow is gone.

Electricity Meter – With solar panels, your electricity meter is bi-directional, meaning that it keeps a count of how much electricity you use from the grid and how much electricity you send to the grid. You may already have a bi-directional meter or your hydro company will take care of replacing your current meter with a new bi-directional one when you get a solar system.

Electrical Panel – Your electrical panel contains circuit breakers that distribute electricity to the various loads throughout your home. Electricity generated by your solar system flows through the inverterA 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. and into the electrical panel, where it supplies your home's electrical loads along with the grid. When you get a solar system, your electrical panel is fed by two sources of electricity.

Electrical Loads – Electrical loads use electricity from the grid or your solar panels. This could be lights, computers, your oven, your dryer or the fan in your furnace. Anything that uses electricity.

The grid consists of transmission and distribution power lines and is responsible for delivery of electricity to homes and buildings. Since solar PV produces electricity on site, it reduces your reliance on the grid. However, most homes with solar panels are still connected to the grid.

For grid-connected solar systems without a battery, the electrical grid effectively acts as a battery, allowing your home to export excess electricity and import power when needed. Because the grid provides this flexibility, most solar installations do not require batteries.

Solar panels and batteries are often thought of together, but most residential solar systems in Canada are grid-tiedA 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. and installed without batteries. Grid-tiedA 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. solar systems provide energy when the sun is shining, helping to offset your home's electricity use and even selling extra energy back to the grid for credit. This typically provides the best payback, however, when the power goes out, so does your solar system. For most homeowners, the power is not out long enough for the cost of batteries to be worth it. For those who are less focused on payback and more interested in backup power during outages or increasing energy independence, adding a battery may make sense.

So when does it make sense to install a battery and when is it better to remain grid-tiedA 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.? See our battery section for more information.

When your solar arrayThe complete group of solar panels (modules) installed together on a roof or ground-mount that work as a single system to generate electricity. is producing electricity during the day and your home is using power, that solar electricity is used first within your home. This directly replaces electricity that would otherwise be imported from the grid, reducing your hydro bill.

When your solar arrayThe complete group of solar panels (modules) installed together on a roof or ground-mount that work as a single system to generate electricity. produces more electricity than your home is using, the excess power is exported to the grid. This is referred to as net meteringA 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.. Your electricity meter tracks this exported energy, allowing you to receive credits on your hydro bill. While these credits do not result in a cash payout, they can be carried forward and applied to future hydro bills for a year, after which they expire. This is why it is important to size your solar system to your home's annual electrical usage.

On cloudy days or at night, the solar arrayThe complete group of solar panels (modules) installed together on a roof or ground-mount that work as a single system to generate electricity. won't produce enough electricity to meet your electrical needs. In this situation, you import electricity from the grid as you did before getting solar. You are paying for this electricity in the same way as before you had solar. Although your total bill is less, due to the two situations above.

Note: If you are interested in a battery system, the above will likely look quite different. Please see the battery section.

Solar electricity is produced when sunlight hits a solar panelA device made up of photovoltaic cells that converts sunlight into DC electricity. Solar panels are also referred to as modules. and creates an electrical current that flows into your home. The amount of electricity produced changes throughout the day and year and is measured in kilowattA 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.-hours (kWh). How much solar electricity your system produces depends on factors such as sunlight, roof tilt (pitch), roof orientation, all sorts of shading and the layout of your solar panels on your roof.

A 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. is a unit of energy that measures how much electricity is used or produced over time. For example, if your solar system produces 1 kWh, that is enough energy to run a 1,000-watt appliance for one hour or a 100-watt light bulb for ten hours.

Solar potentialA 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. is often expressed as kilowattA 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.-hours per kilowattA 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. (kWh/kW). This metric describes how much electricity a solar system produces over a year for each kilowattA 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. of installed capacity. In simple terms, it shows how productive a roof is independent of system size.

In the GTHA, most residential roofs fall within a typical range of 900–1,200 kWh, on average per kW, per year. The average solar potentialA 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. of a region comes from its latitude (its position in relation to the sun) and the overall effect of that region's weather patterns (snow and clouds are shading!).

Besides the region's overall solar potentialA 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., each home will have its own factors that affect its unique solar potentialA 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.:

• Roof tilt or pitch: The steeper the angle of our roof, the more production it will make, but also more difficult it is to install on.
• Roof orientation: South-facing roofs perform best, while east- and west-facing roofs can still have meaningful production.
• Localized shading: Roof penetrations, trees, nearby buildings and even another part of your roof can reduce solar production.

Your HSA Advisor will provide an estimate for your roof's expected annual production using solar design software that will account for your region's solar potentialA 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. and model your home's unique solar potentialA 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.. For example, a home that is modeled to have a solar potentialA 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. of 1,100 kWh/kW would be expected to produce approximately 5,500 kWh per year from a 5 kW system or 11,000 kWh per year from a 10 kW system. Higher values generally indicate better sun exposure, while lower values reflect shading or less favourable roof orientation.

Because solar potentialA 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. plays a major role in projected savings, it's important that it is realistic and well-supported. When a solar quote is prepared, specialized software is used to estimate how much electricity the system is expected to produce each year, measured in kilowattA 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.-hours (kWh).

In some cases, an installer's production estimate may be overstated to make a project appear more attractive or understated to justify a larger system size. While solar production estimates are never exact, they should fall within a reasonable range for the GTHA.