Optimal Angle and Mounting Considerations for Solar Panels on Sloped Roofs in Singapore

In Singapore’s hot and humid climate, solar energy adoption has seen a sharp rise—particularly among landed homeowners and commercial property owners aiming to reduce reliance on the national grid. For these properties, proper installation design is critical to achieving maximum solar output, especially when dealing with sloped roofs.

This article explores the optimal tilt angle, installation feasibility on sloped roofs, and the types of mounting systems required, all within the context of Singapore’s weather, latitude, and roof structures—excluding HDB flats, which follow a different regulatory framework.

Summary Table: Sloped and Flat Roof Solar Panel Installation in Singapore

---

1. What Is the Optimal Tilt Angle for Solar Panels in Singapore?

Singapore lies almost directly on the equator, at approximately 1.35°N latitude. This proximity to the equator means the sun is nearly overhead throughout the year. As such, solar panels in Singapore can perform efficiently across a wide range of tilt angles. However, to maximise energy yield, particularly during overcast days and seasonal variations, an optimal tilt must still be considered.

Optimal Tilt for Maximum Output

• Latitude Rule of Thumb: The most common rule of thumb for panel tilt is to match the angle with the location’s latitude. In Singapore, that would be around 10° to 15°.

• Year-Round Optimisation: A tilt of 10°–15° allows rainwater runoff (which helps clean the panels) while balancing solar gain throughout the year.

• Seasonal Adjustments Not Required: Unlike in temperate countries, there is minimal seasonal difference in solar altitude, so there’s no need to adjust the tilt throughout the year.

Practical Considerations

• Self-Cleaning: A minimum tilt of 10° is recommended to allow water and debris to slide off. Panels mounted flatter than this may accumulate dirt and require frequent maintenance.

• Wind Resistance: Lower tilt angles tend to be more stable against strong wind loads—a relevant concern given Singapore’s exposure to occasional monsoon winds.

---

2. Can You Install Solar Panels on the Flat Side of a Sloping Roof?

Yes, it is technically possible to install solar panels parallel to the flat surface of a sloped roof, depending on the orientation and pitch of the roof.

Key Considerations:

A. Roof Orientation (Azimuth)

• The ideal orientation for solar panels in Singapore is true south-facing (180° azimuth).

• If your sloped roof faces east or west, you can still install panels, but you’ll typically see 10–20% less annual output compared to south-facing arrays.

• Dual-orientation setups (east-west) can help spread power generation throughout the day, useful for properties with morning and evening consumption peaks.

B. Roof Pitch

• If your roof already has a natural slope between 10° and 30°, and it faces the right direction (i.e., south), then flush mounting the panels directly onto the roof surface is both efficient and cost-effective.

• Roofs with very steep angles (above 35°) may require special brackets or reduced panel spacing to avoid shading between rows.

C. Shading and Obstructions

• Check for potential obstructions such as water tanks, chimneys, or nearby buildings that may cast shadows on the roof at different times of the day.

• A proper solar shading analysis using tools like PVsyst or Helioscope is recommended before proceeding.

D. Panel Cooling

• Mounting the panels too closely to the roof can increase their temperature, reducing output. Elevated racking (even 100–150 mm above the roof) improves air circulation and heat dissipation.

Looking to install solar panels for your landed home or business in Singapore? Visit First Solution Group for a free site survey and consultation with our BCA-certified engineering team. We’ll help you maximise output—without compromising your roof’s safety or aesthetics.

---

3. What Type of Mounting Structure Is Required for a Sloping Roof?

When installing on a sloped roof, the mounting structure plays a vital role in ensuring the panels remain secure under load while achieving the desired tilt and orientation.

Types of Mounting Systems for Sloped Roofs:

A. Rail-Based Flush Mounting (Most Common)

• This system involves aluminium rails fixed parallel to the roof slope, to which the solar panels are attached.

• Ideal for pitched metal roofs or tiled roofs.

• Pros:

  • Low-profile and aesthetically pleasing.

  • Strong wind resistance.

  • Cost-effective.

• Cons:

  • Tilt is restricted by the roof pitch.

  • Harder to optimise tilt if the roof is too flat or too steep.

B. Tilted Racking Systems

• Used when the existing roof pitch is too flat (below 10°) or misaligned with the sun.

• These systems raise the back end of the panels to achieve the desired tilt, often using triangular aluminium brackets.

• Suitable for flat roofs or gently sloped roofs (under 10°).

• Pros:

  • Maximises energy output.

  • Allows south-facing orientation regardless of roof slope.

• Cons:

  • Slightly more expensive due to additional materials.

  • May require ballast or enhanced anchoring, especially in high-wind zones.

C. Clamp-Based Mounting for Standing Seam Roofs

• For standing seam metal roofs, solar modules can be installed without roof penetration using clamp mounts that grip the seams.

• Preserves waterproofing and roof integrity.

• Ideal for industrial or modern residential homes with standing seam designs.

Important Local Considerations:

• PE Endorsement Required: In Singapore, all solar mounting structures must be endorsed by a Professional Engineer (PE) to meet BCA and SCDF regulations. Structural load checks are mandatory.

• Corrosion Resistance: Given Singapore’s humidity, all racking systems should use anodised aluminium or hot-dip galvanised steel to prevent rusting.

• Lightning Protection: Integrating lightning arrestors is highly recommended due to Singapore’s frequent thunderstorms.

4. What If the Roof Is Too Flat or Faces the Wrong Direction?

Even if your roof has a minimal slope or an unfavourable orientation (e.g. facing north), solar installation is still possible. Here’s how:

A. Tilt-Up Mounting Structures

• These are elevated brackets that allow the solar panels to be tilted independently of the roof angle.

• Typically angled at 10° to 15°, aligned toward the south for optimal exposure.

• Used on flat concrete roofs or gently sloped roofs (<10° pitch).

• Anchoring Options:

  • Mechanical Anchoring: Bolted directly into the roof slab with waterproofing maintained.

  • Ballasted Mounts: Uses weight blocks to hold the panels in place, ideal when drilling into the roof is not advisable (e.g. rooftop waterproof membrane or warranty restrictions).

B. Design Considerations

• Row spacing is crucial to prevent inter-row shading. This is calculated using the tilt angle and the sun’s lowest winter angle (around 66° solar elevation at noon in Singapore).

• Panels may require custom layouts if rooftop equipment like water tanks or aircon compressors obstruct installation zones.

---

5. Roof Material Compatibility and Anchoring Safety

Before installing any solar panels, you must assess whether your existing roof material is suitable for supporting the extra weight and fixings.

A. Common Roof Types in Singapore’s Landed Properties

B. Anchoring and Waterproofing

• Mechanical anchors must be PE-certified and installed with EPDM rubber seals or flashing to maintain the roof’s waterproof integrity.

• For concrete roofs, chemical anchors with corrosion-resistant bolts are preferred.

• Avoid drilling into aged clay tiles or asbestos roofing, as these may crack or pose health hazards respectively.

---

6. Wind Load and Structural Safety

Given Singapore’s exposure to heavy thunderstorms and occasional strong winds, wind uplift must be factored into the system design.

A. PE Structural Calculations

• All solar mounting systems must be certified by a Professional Engineer (PE) under BCA guidelines.

• PE assessment includes:

  • Wind uplift pressure based on EN 1991-1-4

  • Dead load and live load checks

  • Load transfer to purlins or concrete slab

B. Wind Zone Considerations

• Properties near the coast (e.g. East Coast, Pasir Ris) or in elevated areas like Bukit Timah may face stronger wind exposure.

• In such cases, low-profile flush mounts or increased ballast weight may be required to ensure panel stability.

---

7. Maintenance Considerations for Long-Term Performance

Solar panels are low-maintenance by design, but Singapore’s humid climate and rainfall mean certain precautions should be taken to preserve efficiency.

A. Cleaning Schedule

• Minimum: Twice a year

• If your property is near expressways or industrial zones, consider quarterly cleaning due to faster dust build-up.

• Avoid harsh chemicals. Use soft brushes and water or contact professional solar cleaning services.

B. Inverter and Cable Check

• Most solar issues arise from inverter faults or degraded DC cables.

• Perform annual inspections of junction boxes, inverter terminals, and cable insulation.

C. Panel Degradation

• Most Tier-1 panels degrade at ~0.5% per year.

• By year 25, expect ~87% of the original rated output.

• If degradation is faster, it could indicate heat damage from poor ventilation or persistent shading.

---

8. Lightning Protection and Fire Safety

Due to the high lightning activity in Singapore, a proper lightning protection system (LPS) is essential.

A. Surge Protection Devices (SPDs)

• SPDs are required in DC combiner boxes and at the inverter AC output.

• They help protect sensitive electronic components during surges.

B. Earthing and Bonding

• All metallic racking must be electrically bonded and earthed.

• Compliant systems must meet SS555:2018 standards and be verified during commissioning.

C. Fire-Rated Cables

• Use TÜV-certified DC cables with halogen-free insulation, which reduces toxic fumes during fire events.

• Cable trays must be UV-resistant and rated for prolonged rooftop exposure.

---

9. Compliance and Permits in Singapore

All solar systems, regardless of size, must comply with EMA and BCA regulations:

A. Building and Structural Approval

• Submit a structural submission to BCA if the mounting affects the structural integrity of the roof or building.

• PE endorsement is mandatory for systems exceeding 10 kWp.

B. Connection to SP Group Grid

• If you wish to export surplus energy under SolarNova or Open Electricity Market (OEM), a Connection Agreement must be signed with SP Group.

• Installation must be carried out by a licensed EMA solar contractor.

C. Fire Safety Regulations

• For buildings with fire command centres, solar installations must not block fire access paths or hydrant access.

• SCDF may require submission of fire safety plans, especially for commercial buildings.

---

Final Thoughts

Installing solar panels on sloped or flat roofs in Singapore requires careful planning—but when done right, it offers significant long-term energy and cost savings. With the right tilt, mounting system, roof compatibility, and local regulatory compliance, your solar system can perform efficiently for decades in Singapore’s tropical climate.

If you’re planning to install solar panels on your landed home or commercial property, ensure your installation partner is experienced with PE endorsements, regulatory filings, and tropical-climate engineering.