Is my roof good for solar?

A good solar roof has unshaded area facing south, a pitch between 15° and 40°, and at least 10 years of remaining life. Shading matters most — a single badly placed tree can cut output by a third, far more than orientation ever will.

The six factors, in order of impact

1. Shading — the big one

Panels are wired in series, so shade on one panel can drag down a whole string. Trees, chimneys, neighbouring buildings and even a satellite dish matter. Microinverters or optimisers mitigate this but don't eliminate it. Google's imagery accounts for shading, which is why the sunlight hours we report are lower than raw daylight figures.

2. Orientation

In the northern hemisphere, south-facing is best. East and west-facing roofs produce roughly 10–20% less — often still worth doing, and sometimes preferable if your utility pays more during evening peak. North-facing is generally not worth it.

3. Pitch

Between 15° and 40° is ideal. Flat roofs work with tilted mounting frames at extra cost. Very steep roofs raise labour costs and can shade each other at low sun angles.

4. Roof age and material

Replace the roof first if it has under 10 years left. Removing and reinstalling an array to reroof costs $2,000–5,000. Asphalt shingle is easiest; tile and slate are more expensive and more fragile; standing-seam metal is excellent because panels clamp on without penetrations.

5. Usable area

You need roughly 21 sq ft per 400W panel, plus fire-code setbacks from ridges and edges — typically 3 ft, which removes more area than people expect on small roofs.

6. Structural condition

An array adds about 2–4 lbs per sq ft. Most roofs handle this fine, but older or damaged framing may need an engineer's sign-off.

Check yours in about ten seconds

Rather than guessing at any of this, enter your address — Google's aerial and 3D imagery reports your roof's usable area, how many panels fit, and its actual measured sunlight hours after shading.

What this looks like in real cities

Measured rooftop data, spanning the range from fastest to slowest payback we have found:

City	Sun hrs/yr	Rate	Payback
Honolulu, HI	1,787	42.1¢	3.1 yrs
San Jose, CA	1,810	31.2¢	8.8 yrs
Savannah, GA	1,646	14.1¢	10.4 yrs
Knoxville, TN	1,514	12.1¢	12.8 yrs
Gatineau, QC	1,291	7.9¢	33.3 yrs

See all 209 cities →

Frequently asked

Can I put solar on a north-facing roof?

Technically yes, but output drops 25-40% in the northern hemisphere and payback usually stops making sense. East or west-facing sections are a much better option if available.

Do solar panels damage your roof?

A properly flashed installation should not. Leaks come from poor workmanship, so use an installer who warranties the roof penetrations, not just the panels.

Can I get solar on a flat roof?

Yes, using ballasted or tilted mounting frames. It costs a little more and panels must be spaced to avoid shading each other.

Check your own roof free →

General information, updated 2026-08-22. Not financial, tax or engineering advice.