Is my roof suitable for solar

Not every roof is a good fit for solar, and that is fine. A quick look at a few factors can tell you whether it is worth getting a detailed estimate. This checklist covers the main ones.

Direction

In Canada, the sun sits in the southern part of the sky, so direction matters.

East- and west-facing roofs can still make sense. West-facing panels produce more in the late afternoon, which can help on rate plans with higher evening prices. North-facing slopes are rarely worth using unless the pitch is very shallow.

Pitch

The angle of your roof affects production, but most common residential pitches work reasonably well. A moderate slope usually performs well across the year and helps snow slide off.

Very shallow roofs lose a little output and may hold snow longer. Very steep roofs can lose some summer output and can be harder and more expensive to install on.

Shade

Shade is often the deciding factor. Look at your roof at different times of day and, if possible, in different seasons.

• Trees to the south, east or west can shade panels for hours. Deciduous trees drop their leaves in winter, but winter sun is low so branches still cast shadows.
• Chimneys, vents and dormers cast smaller shadows that move across the roof during the day.
• Neighbouring buildings can block low winter sun, especially in dense areas.

Even partial shade on a few panels can reduce output on the whole string, unless the system uses microinverters or optimizers. See panels and inverters.

Roof age and condition

Solar panels last a long time, often 25 years or more. Removing and reinstalling them to replace a roof adds cost.

If your roof is within roughly 10 years of the end of its life, it is usually smarter to replace it first. Asphalt shingle roofs are the most common in Canada, and their lifespan varies with quality and climate. A roofer can tell you how much life yours has left.

Roof material

• Asphalt shingles are the most common and the simplest to install on.
• Metal roofs, especially standing seam, can be very good for solar, sometimes with clamps instead of roof penetrations.
• Tile, slate and cedar shake are possible but more complex and often more expensive. Not every installer works with them.

Structure

Panels and racking add weight. Most modern homes can handle it, but older homes or unusual framing may need a structural review. Your installer, and sometimes your municipality, will check this during design and permitting.

Flat roofs

Flat roofs can work well. Panels are mounted on tilted racks, which lets the installer point them south at a good angle. Racks are often held down with ballast weight, so structural capacity matters even more. Spacing between rows is needed to avoid panels shading each other.

Usable space and setbacks

Fire codes and local rules may require clear pathways along ridges and edges, called setbacks. These reduce usable area, especially on smaller or cut-up roofs. A roof with many angles, skylights and vents may fit fewer panels than it first appears.

Condos and townhouses

• Condos usually can't install solar individually, because the roof is common property managed by the condominium corporation. Any project would need board approval.
• Freehold townhouses can often go solar, but the roof section is small and may be shaded by neighbouring units. Check any shared roof or party wall arrangements.
• Condo townhouses usually follow condo rules, so speak with your board first.

When solar likely does not make sense

• The only usable roof faces north.
• Heavy shade covers most of the roof for much of the day.
• The roof needs replacing soon and you are not ready to replace it.
• Your electricity use is very low, so there is little to offset.

Next step

See how your roof scores on direction, pitch and shade: check your roof.