How solar power works, from sunlight to your outlet

A solar panel has no moving parts. It sits on the roof, sunlight lands on it, and a trickle of electricity starts to flow. Everything else in a home solar system exists to make that trickle usable, safe and measurable.

The photovoltaic effect in one paragraph

Each panel is a grid of silicon cells. When light hits a cell, it knocks electrons loose from the silicon. The cell is built with two layers treated so that the freed electrons are pushed in one direction, and that steady push is an electric current. Wire sixty or more cells together and you get a panel that produces usable voltage. Sunlight in, direct current (DC) out. Nothing is burned and nothing is consumed.

Panels are rated in watts under standard test conditions. A modern residential panel is commonly rated somewhere between 400 and 450 W, and its efficiency, the share of sunlight it converts, is typically about 20 to 23 percent. The panel types guide explains why nearly everything sold today uses the same basic cell design.

From the roof to your appliances

Think of five steps.

1. The array

Several panels wired together are called an array. A 7 kW system on a two-storey house might be sixteen or seventeen panels spread across the south, east and west slopes. Wiring the panels in series adds voltage, and the combined DC runs down in cables to the inverter.

2. The inverter

Your house runs on alternating current (AC), so DC has to be converted. The inverter does that job. It also tracks the best operating point of the array as light changes through the day, and it watches the grid. Some systems use one string inverter for the whole array, others put a small inverter behind each panel. The string versus microinverter comparison covers the trade-offs.

3. The electrical panel

AC from the inverter feeds into your breaker panel. Your home uses that power first, because electricity takes the shortest path. If the dishwasher, fridge and lights draw 1.5 kW while the array produces 4 kW, the house takes its 1.5 kW and the remaining 2.5 kW heads out to the grid.

4. The meter

The utility meter, or a replacement bidirectional meter installed during connection, records both directions of flow. What you draw is recorded as imports. What you send out is recorded as exports. How those exports are credited depends on your province and utility, and the net metering article shows how different the rules can be.

5. The grid

The grid is the balancing partner. When the sun sets, or on a dark December afternoon, you draw from the grid as you always did. When your roof makes more than you need, the surplus helps power your neighbours. For most homes, that is the whole system: panels, inverter, meter, grid.

What happens at night, in clouds and in snow

At night, nothing is generated. This is normal and is not a fault. Your home simply buys electricity from the utility, or uses stored energy if you have a battery. The battery basics page explains what a battery changes and what it does not.

In cloud, output drops but does not vanish. Panels capture diffuse light, so a heavily overcast day might yield well under a third of a clear-day figure. Over a year, long summer days do most of the work.

Cold is not the enemy that people expect. Solar cells actually run a little more efficiently when cool, which is why a sharp, clear day in February can produce better per-hour output than a hot July afternoon. What cuts winter production is the short day, the low sun angle and snow cover. Panels are tilted, so snow tends to slide off, and the winter performance guide goes into the numbers.

Why your system shuts off in a blackout

This surprises many owners. A standard grid-tied system stops producing when the grid goes down. The reason is safety: if your inverter kept pushing power onto a dead line, it could injure a line worker repairing it. This protection is called anti-islanding and it is required.

To keep lights on during an outage you need a battery and an inverter designed for backup operation, wired so that a defined set of circuits is isolated from the grid. That is a different, more expensive system than a basic grid-tied one.

How much energy to expect

A useful rule of thumb is that each kilowatt of panels in southern Canada often produces roughly 1,100 to 1,400 kWh a year, depending on location, roof angle and shading. That is a typical range, not a promise, and any installer should be able to show you a site-specific estimate and the assumptions behind it. If your household uses, say, 10,000 kWh a year, a system of around 7 to 9 kW could offset most of it on paper. The article on how many panels you need walks through that calculation.

Safety, permits and certification

Solar panels, inverters and wiring are part of your home’s electrical installation. In Canada that means a permit, an inspection by the relevant authority, and equipment that carries a recognised certification mark such as CSA. The electrical code also includes rapid shutdown requirements that let firefighters de-energize the roof wiring quickly. A reputable installer will handle the permit paperwork and the utility application, and should hold the electrical and any provincial licences required.

Where to go next

Once the basics make sense, the practical questions follow: is it worth the money, how big should the system be, and what will it cost. You can find the rest of the foundations in our solar basics hub.