Every year, from roughly November to March, the Harmattan wind carries fine Saharan dust across West Africa. Skies turn hazy, cars gather a film of dust, and solar panels quietly lose output. Many owners only notice when their batteries stop reaching full charge or their inverter switches to grid earlier in the evening than usual.
The good news is that Harmattan losses are largely preventable. A little understanding and a simple maintenance routine will keep your system performing through the dusty season.
How Much Does Dust Really Affect Solar Output?
More than many people expect. A 2023 study in the journal Applied Energy by Isaacs and colleagues found that soiling losses in the most affected West African locations can exceed 50% during the Harmattan season.
Research in Maiduguri, North-East Nigeria, published through Cranfield University, recorded more than a 50% loss in power output from panels left under continuous dust deposition for 14 days.
Losses vary by location, panel tilt, rainfall and local dust sources. Northern states usually see heavier dust, but homes and businesses in southern cities feel the effect too.
Two Ways Harmattan Reduces Output
Dust on the panel surface
Dust settles on the glass and blocks sunlight from reaching the cells. Because panels are wired in series, heavy soiling on part of a panel can reduce the output of the whole string.
Haze in the atmosphere
Even clean panels produce less when the air is full of dust, because less sunlight reaches the ground. You cannot clean the sky, but you can make sure the light that does arrive is not blocked a second time by dirty glass.
How Often Should You Clean Your Panels?
There is no single answer, but during Harmattan:
- Check panels weekly, visually or through your inverter app.
- Clean when you see a visible film or a noticeable drop in daily production compared with similar sunny days.
- In heavily dusty areas, cleaning every one to two weeks may be needed.
Your inverter's monitoring app is the best guide. If production drops while the weather looks similar, dust is the likely cause.
How to Clean Solar Panels Safely
Before you start
- Safety first. Roof work is dangerous. If panels are not safely reachable from the ground or a secure platform, use a professional.
- Clean early morning or late evening, when panels are cool. Cold water on hot glass can stress it.
- Do not walk on panels.
What to use
- Soft brush, sponge or microfibre cloth, ideally on an extension pole.
- Clean water. Where water is hard, rinse with clean, soft water to avoid leaving deposits.
- If needed, a small amount of mild, non-abrasive soap.
What to avoid
- Pressure washers, which can damage seals and coatings.
- Abrasive pads, scouring powders or harsh detergents.
- Sharp tools to scrape off bird droppings. Soak and wipe gently instead.
Check your panel manufacturer's cleaning guidance, as some warranties specify approved methods.
The Rest of Your Harmattan Checklist
Dust is not only a panel problem. Before and during the season:
- Inverter ventilation: dust clogs fans and vents, causing inverters to overheat. Gently clean vents and keep the inverter room tidy.
- Battery area: keep it clean, dry and ventilated. Dust and heat shorten battery life.
- Cables and connectors: look for loose connections, cracked insulation or signs of heat damage.
- Mounting structure: check bolts and rails, particularly before strong winds.
- Shading changes: dry-season pruning or new construction can change shade patterns.
- Monitoring data: compare this month's daily production with the same period last year, if you have the data.
Plan Around Lower Harmattan Output
Even with clean panels, haze reduces production. During the season:
- Run heavy loads like pumps and washing machines in the middle of the day.
- Reduce unnecessary night-time loads to protect your battery.
- Consider whether your system has enough panel capacity for dry-season conditions. Good system design allows for seasonal losses from the start, as explained in our solar sizing guide.
If you are using a hybrid inverter, adjust settings so the battery keeps a reserve for night-time essentials. Our hybrid vs off-grid inverter guide explains how source priority works.
Frequently Asked Questions
Should I clean solar panels with soap?
Clean water and a soft brush are usually enough. If you need soap, use a small amount of mild, non-abrasive soap and rinse thoroughly. Avoid harsh detergents and scouring pads.
Can I clean my panels in the afternoon?
It is better to clean in the early morning or late evening, when the glass is cool. Cold water on hot panels can cause thermal stress.
Will rain clean my solar panels?
Rain helps, but Harmattan is the dry season, so there is little rain to wash dust off. Light showers can even leave muddy streaks. Manual cleaning is usually needed during these months.
Does dust damage solar panels permanently?
Ordinary dust mainly reduces output while it sits on the glass. Damage usually comes from cleaning badly, such as scraping, using abrasive tools or walking on panels.
Professional Maintenance
A professional service can safely clean panels, check electrical connections, test battery health and review inverter settings in one visit. 7th Breed provides solar maintenance for homes and businesses. Contact us to book a pre-Harmattan check, or request a quote.
Sources
- Isaacs, S. et al., Dust soiling effects on decentralized solar in West Africa, Applied Energy, vol. 340 (2023).
- Cranfield University repository, Impact of dust on electrical power output of solar PV modules in North-East, Nigeria.