Solar panels need very little maintenance, but they do need to stay clean. In Kenya's dry seasons, dust from unpaved roads, construction, farms and cement works settles on panels and blocks sunlight. Rain washes much of it off in the long and short rains; between them, losses build up.
How much dust costs
Losses depend heavily on the site. Panels near a murram road, a quarry or a busy farm can lose well over 10% in a few dry weeks; panels in a clean, rainy area may lose only a few percent.
| System | Yearly output | Value at its tariff | Value of each 5% lost |
|---|---|---|---|
| 5 kW home, DC2 at KES 28.30 | about 7,000 kWh | about KES 198,000 | about KES 9,900 a year |
| 100 kW business, CI1 day rate KES 22.09 | about 140,000 kWh | about KES 3.1 million | about KES 154,000 a year |
For a home, cleaning a few times in the dry season is a small job worth doing. For a commercial array, regular cleaning often pays for itself many times over.
How often to clean
- Watch the output. Most inverters have an app or display. If output on a clear day falls noticeably below the same kind of day after the last clean, it is time.
- Clean in the dry seasons, typically January to March and July to October, more often near dusty roads or works.
- Let the rains help, but check after them: rain can leave a muddy film at the bottom edge of each panel.
- Bird droppings block whole cells and should be removed promptly, wherever they appear.
How to clean safely
- Safety first. Roof work is dangerous; use proper access and fall protection, or hire a trained team. Never stand on panels.
- Clean early in the morning or late in the afternoon, when panels are cool. Cold water on hot glass can crack it.
- Use clean, soft water and a soft brush or squeegee. Hard borehole water can leave mineral spots; rinse with clean water if possible.
- No abrasive cleaners, scourers or high-pressure jets. They damage the anti-reflective coating and seals and can void the warranty.
- Do not spray the junction boxes or connectors underneath.
Other checks while you are there
- Shade from growing trees or new buildings, which can cut output more than dust.
- Loose or damaged cables, cracked glass and corrosion on frames.
- Vents on the inverter and battery free of dust and insects.
Build it into the plan
For businesses and institutions, put cleaning and inspection in the maintenance contract with a schedule and a simple output report. Our solar payback article allows about 1% of the installed price a year for maintenance, which covers regular cleaning on most sites.
Learn more
- See how many solar panels a house needs for typical system sizes.
- Solar by county shows the monthly sun for your area, including the rainy months.