How much electricity does a solar panel make?

A single 430 W solar panel in Toronto makes roughly 470 kWh a year in our model. That's about 1.3 kWh a day on average, enough to run a fridge for most of a day. The real figure for your roof depends on where you live, which way the roof faces and how much shade it gets.

Output by city

These are our model's figures for a well-placed roof. Per-panel numbers assume a 430 W panel.

The Prairies lead because they get clear, dry skies. Coastal cities get more cloud. Natural Resources Canada's solar maps show the same pattern, with Regina and Saskatoon at the top and St. John's at the bottom.

The seasonal swing

Output changes a lot through the year. Here is our Toronto sample system, scaled to one kW and to one panel.

July produces close to nine times as much as December. May to August makes about 57% of the year's output, while November to February makes about 10%. That's why net metering's rollover of summer credits matters so much in Canada. See solar in Canadian winters and solar panels and snow.

What affects output on your roof

Orientation

South-facing roofs collect the most sun over a year. East and west faces produce less, and west faces shift output toward late afternoon. North faces usually aren't worth covering.

Tilt

Most common roof pitches work well. Very flat or very steep surfaces lose some output, and flat surfaces hold snow longer. See ground mount and flat roof solar.

Shade

Trees, chimneys, dormers and neighbouring buildings can cut output sharply, especially with a single string inverter. A shadow on one panel can drag down others wired with it. See shading and solar and microinverters vs string inverters.

Temperature

Panels make more power when they're cool. A clear, cold spring day can produce more than a hot summer afternoon with the same sunshine. Heat reduces output a little; cold doesn't hurt it.

System losses

Wiring, inverter conversion, dust and small mismatches between panels all cost some energy. Our model takes 14% off the panels' raw output for these losses.

Age

Panels lose a small amount of output each year. Our model assumes 0.5% a year. See solar panel lifespan and degradation.

Panel wattage is not daily output

A 430 W rating is the panel's output under standard lab conditions: strong sunlight at a set temperature. On a real roof, a panel only reaches that briefly, if at all. Yearly kWh is what matters for savings, and it depends on hours of good sun as much as on the rating.

How to check your own estimate

Multiply the system size in kW by the yield for your city, then adjust down for shade or a less-than-ideal direction. Our system size tool does this for you. Once your system is running, compare real output with the estimate month by month, as described in solar monitoring and what to watch.

Next step

See how much your own roof could produce: check your roof.

Common questions

How many kWh does a solar panel produce per day in Canada?

In our model, a 430 W panel averages about 1.0 to 1.5 kWh a day over a year, depending on the city. Summer days produce several times more than winter days.

Which Canadian city is best for solar output?

Prairie cities such as Regina, Winnipeg and Calgary produce the most per kW in our model, about 1,250 to 1,300 kWh a year. Coastal cities such as Vancouver and St. John's produce less because of cloud.

Do solar panels work in winter?

Yes, but output is much lower. Our Toronto sample produces about a ninth as much in December as in July, because days are short, the sun is low and snow can cover panels.

Does hot weather increase solar output?

No. Sunshine increases output, but heat slightly reduces it. Cool, clear days are the most efficient.

Sources

• Natural Resources Canada: Photovoltaic potential and solar resource maps
• Canada Energy Regulator: Which cities have the highest solar potential in Canada?