If you open a solar monitoring app for the first time in January, the graph can look disappointing. If you open it in June, it looks like the system is doing the work of a small power station. Both views are normal. Knowing the yearly shape in advance makes the numbers easier to read and your bills easier to predict.
The shape of the year
Solar production follows the sun’s height and the length of the day. In Canada both change a lot between seasons. In June the sun is high and days are very long. In December the sun is low, days are short, and some mornings are dark when you wake up.
For a typical fixed-tilt system in southern Canada, the rough pattern looks like this:
| Season | Typical pattern |
|---|---|
| Dec to Feb | Lowest output; short days, low sun, possible snow cover |
| Mar to May | Rising quickly; cold, clear days can be productive |
| Jun to Aug | Peak output; long days dominate even when it is hot |
| Sep to Nov | Falling steadily; autumn cloud often cuts it further |
The yearly total for a kilowatt of panels in southern Canada often lands around 1,100 to 1,400 kWh, depending on location and design. Sunnier regions such as southern Alberta and Saskatchewan tend to be at the higher end, and cloudier coastal areas may be lower. Treat that as a typical range, not a promise for your roof.
What a worked example looks like
Take a 7 kW system in a location that yields about 1,250 kWh per kW per year. Annual production would be roughly 8,750 kWh. Rather than dividing that evenly by twelve, consider that summer months may produce several times what the darkest winter month does. A single December might give a few hundred kWh, while a single July might give well over a thousand. These are illustrative figures, and your own estimate should come from a modelling tool run on your address, roof angle and shading.
The point is that a monthly average, about 730 kWh in this case, describes almost no actual month. Compare your own household use, month by month, with the monthly estimate. Your use may be higher in winter if you have electric heating or a heat pump, which widens the gap.
Why winter output is lower than the day length suggests
Several things stack up in winter:
- The sun is low, so light hits the panels at a shallower angle relative to the ground, and travels through more atmosphere.
- Days are short, so fewer hours of generation.
- Cloud is more common in many regions.
- Snow cover can pause production until it slides or melts. See snow on panels for the details.
- Shading from trees, chimneys and neighbouring buildings gets longer when the sun sits low.
Cold itself is actually helpful. Panels run a little more efficiently when cool, which is why a crisp, clear March day can give a pleasant surprise. For the broader winter picture, our guide to solar in Canadian winters goes further.
Tilt and orientation
A steeper tilt favours winter, and a shallower tilt favours summer. Most residential systems follow the roof pitch, which is a compromise that works fine. A south-facing roof gives the most output over the year, while east-west roofs spread production more evenly across the day at a somewhat lower total. If you are weighing a ground mount, you can choose the tilt more freely, as described in roof, ground and carport mounting.
How the monthly swing hits your bill
The effect depends on how your utility credits exports.
Under net metering with rollover credits, extra production in summer is banked and used against winter consumption. A system sized for your yearly use can bring many annual bills close to zero, even though a given winter bill is still real. In some provinces the arrangement is closer to net billing, where exports earn a lower rate than you pay for imports. Summer surplus is then worth less, and winter bills stay higher. We explain the variants in net metering across Canada. Rules and caps change, so confirm current terms with your utility.
Time-of-use rates add another layer. Summer afternoons can be a high-price window, which may boost the value of midday production, and winter evenings are often expensive with no solar available. See time-of-use rates and solar for how that interacts.
Using the monthly shape to size your system
When you size a system, do not rely on the annual number alone. Ask your installer for a monthly production estimate, and match it against your last twelve months of bills. If most of your use is in winter, you may want a larger system or realistic expectations about the credits. If your use peaks in summer because of air conditioning, solar lines up better. Our guide to how many panels you need walks through the arithmetic.
What to watch in your first year
Record your monthly production and compare it with the estimate. A shortfall of a few percent in any one month is normal, because weather varies year to year. A large gap that persists could mean shading, a fault or a poor estimate. Check the inverter display and any alerts first, and then contact the installer if it continues.
For more on seasonal care and conditions, see the cold climate hub. Once you see the pattern a few times, the summer highs and winter lows stop being surprising and begin to look like a calendar.
Quick answers
How much less do panels produce in December?
Often a small fraction of a peak summer month, depending on latitude, snow and roof angle. Short days and a low sun both cut output.
Which month is best for solar in Canada?
Usually June or July, though a clear, cool spring month can compete. Heat slightly lowers panel efficiency, but long days dominate.
Can I trust the monthly figures in a quote?
Treat them as modelled estimates. Ask which tool and weather data were used, what tilt and shading were assumed, and whether snow was included.
Where to verify
Rules and prices change. Confirm current details with the official bodies below.