Irradiance Profile
Monthly Irradiance Detail
| Month | PSH (h/day) | Daily kWh/m² | Monthly kWh/m² | Total Energy (kWh) |
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How to Use the Solar Irradiance Calculator
Each city loads its latitude and annual average peak sun hours from Canadian solar resource data. This sets the baseline horizontal irradiance before tilt and orientation corrections are applied.
Leave tilt blank to default to latitude tilt, the typical optimal angle for year-round capture. Choose south for the highest annual irradiance in the Northern Hemisphere, or select another orientation to see the reduction.
Enter the area of your solar PV array or thermal collector in square metres to see total daily and monthly energy in kWh, not just the per-square-metre irradiance value.
The chart and table show how irradiance varies through the year. Use this data directly as an input to the solar PV HVAC calculator or solar thermal calculator.
Understanding Solar Irradiance Across Canada
Solar irradiance data is the foundation of every solar system calculation, whether for PV electricity generation or solar thermal heat collection. Despite Canada's reputation as a cold, cloudy northern country, much of its populated southern region receives solar resource comparable to Germany, which has one of the world's largest installed PV capacities. Understanding how irradiance varies by location, season, tilt, and orientation is essential to accurate solar system sizing.
Peak sun hours as the standard sizing metric
Solar irradiance is technically measured in watts per square metre (W/m²), a power unit that varies continuously through the day from zero at sunrise to a peak around solar noon and back to zero at sunset. For system sizing, this varying curve is converted into peak sun hours (PSH) — the number of hours of standard 1,000 W/m² intensity that would deliver the same total daily energy as the actual variable sunlight. A location with 4 PSH per day receives the equivalent of 4 hours of full-intensity sun, even though actual daylight might last 10 to 16 hours depending on season and latitude. PSH is numerically identical to daily insolation in kWh/m²/day, which makes it directly usable in array sizing calculations.
Why Calgary and the Prairies outperform coastal cities
Calgary, Regina, Saskatoon, and Medicine Hat consistently rank among Canada's sunniest cities, with annual average PSH of 4.4 to 4.6. This isn't because they're further south — Calgary at 51°N is actually further from the equator than Toronto at 43.7°N. The driver is climate: the Prairie provinces have a dry continental climate with fewer cloudy days than the more humid regions near the Great Lakes or the Pacific and Atlantic coasts. Vancouver, despite its mild winters, has lower annual irradiance (3.5 PSH) due to persistent cloud cover, especially in winter months. This means a PV system in Calgary will produce roughly 25 to 30% more annual energy than an identical system in Vancouver.
How tilt angle changes annual and seasonal capture
A south-facing surface tilted at an angle approximately equal to the local latitude captures close to the maximum possible annual irradiance, because this angle keeps the surface roughly perpendicular to the sun's average position throughout the year. Tilting steeper than latitude (latitude + 10 to 15°) trades some summer capture for improved winter capture, which is useful for space heating applications where winter demand dominates. Tilting shallower (latitude - 10 to 15°) does the opposite, favouring summer collection — useful for pool heating or cooling-dominated loads. The difference between optimal and suboptimal tilt is usually only 5 to 10% annually, but the seasonal redistribution can be 20% or more between summer and winter months. Use the solar orientation calculator to compare specific tilt and azimuth combinations side by side.
GHI, DNI, and POA — which irradiance value matters
Solar resource data comes in several forms. Global Horizontal Irradiance (GHI) is the total radiation hitting a flat, horizontal surface, combining direct beam and diffuse sky radiation. Direct Normal Irradiance (DNI) measures only the direct beam component, tracked perpendicular to the sun — relevant mainly for concentrating solar technologies that aren't common in Canadian residential or commercial applications. Plane of Array (POA) irradiance is what actually reaches a tilted collector at its specific angle and orientation, accounting for both the geometric relationship to the sun and the ground-reflected component (albedo), which becomes more significant with Canadian snow cover in winter. This calculator estimates POA irradiance from your selected tilt and azimuth, which is the figure relevant for sizing PV arrays and solar thermal collectors.
Winter snow albedo: an underappreciated Canadian advantage
Fresh snow reflects 80 to 90% of incident sunlight, compared to 15 to 25% for typical ground surfaces. A steeply tilted collector — such as a vertical or near-vertical solar thermal panel — can capture meaningful additional irradiance from ground-reflected light bouncing off snow cover in winter. This effect partially offsets the low winter sun angle in Canadian climates and is one reason steeper winter-biased tilts perform better than the simple geometric calculation alone would suggest. This calculator's tilt correction includes a modest winter albedo boost reflecting this Canadian-specific effect.
Frequently Asked Questions
Solar irradiance is the power of sunlight hitting a surface, measured in watts per square metre (W/m²). For solar system design, the more useful figure is solar irradiation or insolation, which is irradiance integrated over time and expressed in kWh per square metre per day. This is numerically equal to peak sun hours (PSH), since one peak sun hour represents one hour of sunlight at the standard test intensity of 1,000 W/m². A location receiving 4 kWh/m²/day has 4 peak sun hours. This calculator provides this data for any Canadian city, adjusted for your collector tilt and orientation.
Among major Canadian cities, Calgary and Regina have among the highest solar resources, averaging 4.4 to 4.5 peak sun hours per day on an annual basis, thanks to their dry prairie climate and frequent clear skies. Medicine Hat, Alberta is often cited as Canada's sunniest city by annual sunshine hours. Coastal cities like Vancouver and Halifax have lower annual irradiance, around 3.5 to 3.7 PSH, due to more frequent cloud cover, despite Vancouver's relatively mild and ice-free winters. Use this calculator to compare your specific city's monthly profile.
A collector tilted at an angle closer to the local latitude generally captures more annual irradiance than a flat or steeply tilted surface, because it sits more perpendicular to the average solar angle throughout the year. Tilting steeper than latitude favours winter capture at the expense of summer, while tilting shallower favours summer at the expense of winter. The difference between the best and worst tilt angle for a south-facing surface is typically only 5 to 10% of annual irradiance, but it matters more when optimising for a specific season like winter heating or summer cooling. The solar orientation calculator compares multiple tilt and azimuth scenarios directly.
GHI (Global Horizontal Irradiance) is total solar radiation on a flat horizontal surface, combining direct and diffuse sunlight. DNI (Direct Normal Irradiance) is the direct beam component only, measured perpendicular to the sun's rays, and is most relevant for concentrating solar technologies. POA (Plane of Array) irradiance is the total radiation actually falling on a tilted collector at its specific angle and orientation, accounting for the geometric relationship between the surface and the sun. PV and solar thermal system design uses POA irradiance, since that's the energy the actual collector surface receives. This calculator estimates POA irradiance from your selected city, tilt, and orientation.
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