Solar panel mounting, direction, tilt and placement in Nigeria
Two identical systems can produce very different amounts of power depending on where the panels sit. Direction, tilt and shade matter, and so does a mounting that survives Nigerian storms. This guide covers the main decisions in plain language, so you can judge a roof and a quote.
Which way to face and how steeply to tilt
Nigeria lies north of the equator, so the sun is in the southern half of the sky for most of the year. For most roofs, the best fixed direction is south.
The best tilt for a year-round system is close to your latitude, and Nigeria runs from roughly 4 to 14 degrees north. In practice, a tilt of about 10 to 15 degrees suits almost the whole country. Do not go much flatter than 10 degrees: dust and water then stay on the glass instead of washing off in the rain.
- A roof facing east or west is often still fine. At low tilts the loss compared with south is usually only a few percent, so do not reject a roof just because it does not face south.
- A roof facing north is the one to avoid at steeper tilts. On a flat roof you can tilt the panels south with a frame.
- Following the roof's own slope is simplest and cheapest. Many Nigerian roofs are fairly low pitched, which suits solar well.
Shade matters far more than a few degrees of direction or tilt. A well-placed, shade-free panel facing east can beat a south-facing panel that sits in shadow all afternoon.
Shade is the biggest enemy
Panels in a string are wired in series, so shade on even one panel can pull down the output of the whole string. Check the roof between about 9 am and 3 pm, which is when most of the energy is made.
- Look for trees, water tanks, parapet walls, satellite dishes, chimneys, vents and taller neighbouring buildings. Remember that trees keep growing.
- Shade moves through the day and the year, so look at the site at different times, or ask the installer to measure it with a shade tool.
- If some shade cannot be avoided, ask about separate strings, microinverters or power optimisers, which stop one shaded panel from dragging down the others.
- Keep panels clear of bird perches and overhanging branches, which add droppings and leaves.
Mounting on different roofs
| Roof | Usual mounting | Watch out for |
|---|---|---|
| Long-span aluminium or zinc sheets | Rails clamped to the sheet ribs with special clamps, or fixed through the ridge. | Drilling through the sheet can cause leaks. Clamps that grip the rib avoid holes. |
| Concrete flat roof | Tilt frames bolted to the slab, or weighted frames. | Waterproofing around bolts, drainage and the load on the slab. |
| Clay or concrete tiles | Roof hooks under the tiles, with rails across them. | Cracked tiles. Each hook must be sealed and properly fixed. |
| Asbestos-cement sheets (older roofs) | Not a job to improvise. | Do not drill, cut or break these sheets. The dust is harmful. If your roof might be asbestos, have it checked by a professional first. |
| Weak or old roof timbers | Strengthen first, or use a ground mount. | Panels and frames add weight and wind load. An engineer or experienced installer should check the structure. |
Wind, storms and salt air
- Nigerian storms can bring strong gusts. Panels act like sails, so the frame must be fixed to the structure, not just to the roofing sheet, with the right number of fixings.
- Near the coast, in Lagos, Port Harcourt and Calabar for example, salt air corrodes cheap steel quickly. Ask for aluminium frames and stainless or hot-dip galvanised fasteners.
- Mixed metals touching each other in damp air can corrode, so the frame and fixings should suit each other.
- Frames and panels should be earthed (bonded) and the system protected against lightning and surges, which are common in Nigeria. Ask your installer how this is done.
Gaps, rows and airflow
- Panels lose some output as they heat up, typically around a third of a percent for each degree above 25 degrees Celsius. Leave a gap behind the panels, often about 10 centimetres on a pitched roof, so air can pass.
- On a flat roof with several rows, the front row must not shade the next. The installer works out the gap from the tilt and panel height. As a rough guide the gap should be at least a few times the height the raised edge of the panel stands above the roof.
- Leave walkways so people can reach and clean panels without stepping on them or the cables.
- Keep cable runs short and tidy, with cables clipped and protected from sun and rain.
Where to put the inverter and batteries
- Put them in a cool, dry, ventilated place out of direct sun and away from flooding. Heat shortens the life of batteries and inverters.
- Keep them close to the panels and the distribution board to keep cables short, but not in a bedroom or other sleeping space.
- Leave clear space in front for isolators and switches, and keep flammable materials away from batteries.
- Keep children and pets away, and make sure the room can be reached easily in an emergency.
- Do not box batteries into an airtight cupboard. They need ventilation.
Working on a roof and with solar wiring is dangerous. Falls, electric shock from the panels' direct current, and poorly fixed panels in storms cause real injuries. Use a qualified installer, and never improvise a roof mounting.
Before you fix panels to a roof
- Check the roof for shade between 9 am and 3 pm, and think about trees that will grow.
- Pick a direction (south is best, east or west is often fine) and a tilt of about 10 to 15 degrees.
- Have the roof structure checked, and do not drill into asbestos-cement sheets.
- Ask for corrosion-resistant frames and fixings, especially near the coast.
- Confirm how the system is earthed and protected from lightning and surges.
- Choose a cool, ventilated, dry place for the inverter and batteries, away from sleeping areas.
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Frequently asked questions
Which direction should solar panels face in Nigeria?
Face them south if you can, because Nigeria is north of the equator and the sun spends most of the year in the southern sky. East or west-facing roofs usually lose only a few percent at the low tilts used here, so they are often still worth using. Avoid shade above all.
What is the best tilt angle for solar panels in Nigeria?
About 10 to 15 degrees works across most of the country. Do not go much flatter than 10 degrees, or rain will not wash dust off. If your roof has a gentle pitch, following it is usually fine.
Can I put solar panels on a flat roof?
Yes. Use tilt frames, fixed to the slab or weighted down, with waterproofing around any bolts and enough space between rows so they do not shade each other. The slab must be able to carry the load.
How much does shade reduce solar output?
A lot more than the size of the shadow suggests. Because panels in a string work in series, shade on one panel can reduce the whole string. Avoiding shade between roughly 9 am and 3 pm is the single most useful placement rule.
Do I need to clean panels more in some places?
In dusty areas, especially in the north during harmattan, panels collect dust faster and may need cleaning more often. A tilt of at least 10 degrees helps rain wash them.