Is My Roof Good for Solar? An Ontario Checklist

Before you compare solar quotes, it helps to know whether your roof is a good candidate. A great roof can make solar pay back in about a decade. A poor one can stretch payback past the life of the panels. You can assess most of the important factors yourself in an afternoon with a compass app, a look at your trees and your home's records.

This guide walks through each factor, explains what "good enough" looks like in Ontario and ends with a simple scoring checklist.

1. Orientation: which way does your roof face?

In Ontario, panels produce the most energy facing true south. But other directions are often still viable.

Roof face	Production compared with south (typical)	Verdict
South	100%	Ideal
South-east / south-west	About 95%	Excellent
East / west	About 85–90%	Good; west can better match evening use
North-east / north-west	Roughly 65–75% (varies with pitch)	Usually marginal
North	Poor, especially on steep roofs	Generally not recommended

For a well-oriented, unshaded array in southern Ontario, a typical yield is roughly 1,100–1,250 kWh per kW of panels per year. An east-west split, with panels on both faces, is a common and reasonable design for homes whose ridge runs north-south.

Tip: Phone compass apps can be thrown off by nearby metal. Check orientation against an online satellite map, which shows your roof lines clearly.

2. Pitch: how steep is your roof?

Most Ontario homes have roof pitches between about 4/12 and 12/12 (roughly 18° to 45°). Panels mounted flush on anything in this range will perform well. Steeper roofs shed snow faster in winter, while shallower roofs gather slightly more summer sun.

Flat roofs can work with tilted racking, which is held down by ballast or attachments. Ballast adds weight, so a structural review is essential. Tilted rows also need spacing to avoid shading each other, which reduces how many panels fit.

3. Shading: the biggest performance factor

Shade from trees, chimneys, dormers, neighbouring buildings and even vent stacks can cut output far more than orientation does. In a traditional string-inverter design, shade on one panel can drag down a whole string. Microinverters or optimizers reduce that loss but add cost.

Check shade at different times of year:

• Summer midday: the sun is high; most shade problems are from tall trees close to the house.
• Spring and fall mornings and afternoons: longer shadows reveal neighbours' trees and buildings.
• Winter: the sun is low and shadows are long, but winter production is small anyway, so modest winter shade matters less.

A good installer will use satellite-based shade analysis or an on-site tool and should show you the estimated annual shading loss in the proposal. As a rough guide, total shading losses under about 10% are fine, 10–20% is worth a careful look, and more than about 25% usually makes the economics poor.

Caution: Cutting down healthy mature trees to make room for solar can increase your summer cooling load and may need a municipal permit. Weigh the trade-off honestly.

4. Roof age and condition

Solar panels typically last 25–30 years. Asphalt shingles in Ontario typically last 15–25 years depending on quality, ventilation and exposure. If your roof will need replacing in the next decade, you will pay to remove and reinstall the panels, which often costs several thousand dollars.

Shingle age / condition	Recommendation
Under 5 years old, good condition	Install solar
5–12 years, good condition	Usually fine; ask the roofer's opinion
12+ years, or curling, granule loss, leaks	Re-roof first, then install solar

If you re-roof first, coordinate the two trades. Some homeowners upgrade underlayment and flashing details under the future array.

Roofing materials

• Asphalt shingle: the most common; standard flashed mounts work well.
• Standing-seam metal: excellent; clamps attach to seams without penetrations, and the roof lasts as long as the panels.
• Corrugated or ribbed metal: workable with the correct mounts.
• Clay or concrete tile, slate, cedar shake: possible but more complex and costly; breakage risk during installation.
• Flat roofs (modified bitumen, TPO, EPDM): workable with ballasted or attached racking; watch membrane warranties.

5. Usable area

Modern residential panels of roughly 400–450 W each measure about 1.9–2.0 m² (about 20–22 sq ft). Allowing for spacing and edges, plan on roughly 5 m² (about 54 sq ft) of clear roof per kW.

Target system	Panels (about 425 W)	Clear roof area needed (approx.)
4 kW	9–10	20 m² (215 sq ft)
6 kW	14	30 m² (320 sq ft)
8 kW	19	40 m² (430 sq ft)
10 kW	24	50 m² (540 sq ft)

Vents, skylights, chimneys and required fire-access setbacks from ridges and edges can reduce usable area considerably. A small, chopped-up roof may support less capacity than its total area suggests.

6. Structure and snow

Panels and racking add roughly 15–20 kg/m² (about 3–4 lb/sq ft) of distributed weight, which most sound roofs carry easily. What matters more in Ontario is snow and wind loading, which vary by location under the Ontario Building Code. A competent installer checks rafter or truss size and spacing, and specifies attachment spacing for your local design loads. Some municipalities require a building permit and engineer-stamped drawings.

Snow also slides off panels more readily than off shingles. Consider snow guards above walkways, entrances and driveways.

7. Your electrical panel

The array connects to your main electrical panel. Older 60–100 A panels, or panels that are full, may need upgrading. This is often discovered at the site visit and can add a meaningful cost. Electrical work must be done under an ESA permit; see esasafe.com (opens in a new tab).

Self-assessment scoring checklist

Give yourself the points for each line that applies:

• Main roof face is S, SE or SW (3 points) or E or W (2 points)
• Little or no shade from 9 a.m. to 3 p.m., March to October (3 points)
• Roof covering has at least 12–15 years of life left, or is new (2 points)
• At least 30 m² of clear, unbroken roof on suitable faces (2 points)
• Electrical panel is 200 A, or 100 A with spare space (1 point)
• You plan to stay in the home for 10+ years (1 point)

10–12 points: strong candidate. 7–9 points: worth getting quotes, but scrutinize production estimates. Under 7 points: solar may not pay back; look at other upgrades first.

Then estimate your savings with our solar savings calculator or request an assessment through our solar hub.

Frequently asked questions

Can I put solar on a north-facing roof?

It is technically possible, but output is low, especially on steeper roofs, and payback is usually poor. A ground mount in a sunny yard, or a south-facing garage roof, may be better options.

Will installing panels void my roof warranty?

It can if the installation is done incorrectly. Ask your roofer and solar installer how penetrations are flashed, and look for an installer who provides a written roof-penetration or workmanship warranty of at least 10 years.

Do I need to clear snow off my panels?

No. Climbing on a snowy roof is dangerous and can damage panels. Snow usually slides off within days after a storm, and winter production is a small share of annual output.

Is a ground-mounted system an option?

Yes, on rural or larger lots. Ground mounts can face due south at the ideal tilt and are easy to clear, but they cost more for racking and trenching and may need municipal approval.