Solar Shading Analysis: Why Even Partial Shade Can Kill Your Solar Investment

You think your roof gets plenty of sun. It faces south. No trees are directly above it. You are ready to go solar.

Then the installer comes out and says your production will be 40% lower than expected. Why? Shading.

Shading is the silent killer of solar ROI. Here is what you need to know before you sign a contract.

How shading affects solar panels

Solar panels work in strings. A string is a group of panels connected in series. When one panel in a string is shaded, it reduces the output of the entire string.

Think of it like a garden hose with your foot on it. Even a small pinch reduces water flow through the whole hose.

This is not a myth. It is how electricity works.

Common sources of shading

Trees — The most common culprit. A tree 50 feet from your house can cast shade on your roof in the morning or evening. Seasons matter too. A tree with full leaves in summer shades your roof differently than in winter.

Chimneys and vents — Even a small chimney can cast shade on adjacent panels. The shade moves throughout the day as the sun changes position.

Neighboring buildings — An apartment complex next door can shade your roof in the morning or afternoon depending on orientation.

HVAC units — A rooftop AC unit casts shade on panels behind it. This is especially problematic on flat roofs.

Gutters and roof edges — Overhanging eaves cast shade on the edge of your roof. Panels placed in these areas produce significantly less energy.

How to check for shading yourself

You can do a basic shading assessment:

1. Stand on your roof at noon — Look for shadows from trees, chimneys, and neighboring buildings.
2. Check morning and evening — Visit your roof at 9am and 4pm on a sunny day. Note where shadows fall.
3. Check seasonal changes — A tree that does not shade your roof in winter may shade it heavily in summer.
4. Use online tools — Google Sun Calculator and other tools show sun paths for your location.

But these are rough estimates. A proper shading analysis requires satellite imagery and software that models sun position throughout the year.

What SolrScan checks for

SolrScan uses satellite imagery to analyze shading on your roof. Our report shows:

• Shading map — Visual representation of shaded vs unshaded areas
• Seasonal shading — How shading changes from winter to summer
• Time-based shading — When during the day shading occurs
• Impact estimate — How much shading reduces your potential production

This information helps you understand whether your roof is suitable for solar before you invest.

What to do if your roof has shading

If your roof has significant shading, you still have options:

1. Microinverters or optimizers — These devices allow each panel to operate independently. If one panel is shaded, it does not drag down the entire string. This costs more upfront but protects your investment.
2. Trim trees — If trees are the problem, trimming or removing them may solve the issue.
3. Use unshaded areas — Place panels only on the unshaded portions of your roof. This means fewer panels but better production per panel.
4. Ground mount — If your yard gets full sun, a ground-mounted system may work better than a roof-mounted one.
5. Skip solar — If shading is too severe, solar may not make financial sense. That is okay. Better to know upfront than after spending $20,000.

The bottom line

Shading is the #1 reason solar systems underperform. Most homeowners do not realize how much shade their roof gets until after installation.

Get a shading analysis before you sign a contract. SolrScan checks shading from satellite imagery for $19. It takes 60 seconds. No account needed. No sales call.

Get your report at solrscan.com.