See where the sun rises, peaks and sets at your site in summer, spring/fall and winter.
Top view: dark bar = shadow of a 1 m post. Yellow dot = sun direction.
Check for shading
Add trees, hills or buildings. Bearings are true (N=0°, E=90°, S=180°); a compass reads magnetic, which differs. Height is above your panels, distance is from them.
Want to see the actual shadows at your site? Shadowmap simulates sunlight and shade in 3D for any location.
Affiliate link: we may earn a commission at no cost to you.
What a sun path calculator shows
A sun path shows where the sun travels across the sky at your location through the year. Pick your city and the chart draws three arcs: summer (June 21), spring and fall (March 20) and winter (December 21). For off-grid solar planning the winter arc matters most. It is the lowest and shortest of the three, and the easiest for trees, hills and buildings to block.
How to read the chart
The centre of the chart is straight overhead. The outer ring is the horizon, and the rings between mark 30° and 60° above it.
N, E, S and W are true compass directions, not magnetic ones. Each arc starts where the sun rises on the east side and ends where it sets on the west side.
The dots on the arcs are hourly positions, and the hours are labelled on the winter arc.
The yellow sun marks the date and time you choose with the sliders. Press Play day to watch it cross the sky and see the shadow of a 1 m post change.
The table lists sunrise and sunset directions, the sun's highest point and the hours of daylight for each season.
Using the winter shade rule
The yellow summary box turns the numbers into a rule you can use on the ground. A tree or building south of your panels casts a shadow about as long as its height divided by the tangent of the sun's height above the horizon. Winter sun is low, so the shadows are long. Near Victoria, for example, you need roughly 4 m of clear space for every 1 m of obstruction height to keep the 10 am to 2 pm sun, and about 7 m to keep 9 am to 3 pm. Your own city will give different numbers.
Then add what is actually on your site under Check for shading. Enter the compass bearings an obstruction covers, its height above your panels and its distance, and the calculator shows how many winter hours it blocks.
Limitations to keep in mind
Simplified obstructions. Each obstruction is treated as a flat-topped block. Sloped tree lines, roof gables and uneven ground are approximated, so enter several obstructions to follow a curved skyline more closely.
Not a production simulator. The calculator shows sun geometry and shading, not kilowatt-hour output. It does not account for cloud, snow cover or dirty panels. For production planning, use the peak sun hours in our tilt angle calculator and our solar panel calculator.
Bare trees still block sun. Leafless deciduous trees typically block somewhere between roughly 15% and 60% of winter sunlight, depending on the species and how dense the branches are. Shade on part of a series string can also cut output by more than the shaded share, and a short string close to your charge controller's minimum input voltage may stop charging altogether. Check that minimum in your controller's manual. When you add an obstruction, choose Bare winter tree to count it as 40% blocked instead of fully blocked.
This is a planning tool, not a site survey. Once you have narrowed down a spot, confirm it with a 3D shading tool or a Solar Pathfinder on the property. When the site is clear, use our solar panel tilt angle calculator to set the angle and see peak sun hours for your city.
Frequently asked questions
Which direction should solar panels face in Canada?
Face solar panels toward true south. In Canada the sun spends most of the day in the southern half of the sky all year, and in winter it rises in the southeast and sets in the southwest. A few degrees off south costs very little, but turning panels toward the east or west reduces winter output, which is the season off-grid systems depend on most.
What is the difference between true south and magnetic south?
A compass points to magnetic north, which is not the same as true north. The gap, called magnetic declination, varies across the country and is more than 15° in many places, so a compass or phone reading can point your panels well away from true south. Look up the declination for your location (Natural Resources Canada offers a free calculator) and correct for it, or find true north by marking the shadow of a vertical stick at solar noon.
How do I check whether trees or buildings will shade my panels?
Use the Check for shading section. For each obstruction, enter the compass bearings it covers, its height above your panels and its distance from them. The chart then shows which parts of the sun's path are blocked, and the table shows how many hours you lose. To measure a tree's height, stand a known distance away, use a phone clinometer app to measure the angle to the top, and calculate height = distance × tan(angle), then adjust for your eye height and the panel height. For an exact answer on a specific property, use a 3D shading tool such as Shadowmap or a Solar Pathfinder on site.
How accurate is the sun path calculator?
The sun position calculation is typically within about a degree. The larger uncertainties are your exact coordinates (city locations are approximate), hills and tree lines the tool cannot see, and the simple flat-topped obstruction shapes it uses. Clock times use the standard time zone for your province, so a few places that follow different local time rules may differ. Treat the results as planning estimates, not a site survey.
Why does the winter sun matter most for off-grid solar?
An off-grid system has to carry your loads through the darkest month. In winter the sun is at its lowest, daylight is shortest and any obstruction blocks a larger share of the day, so a site that looks fine in summer can lose hours of production. Snow and cloud add to the problem. Checking the December 21 arc is the quickest way to see whether a location will work.