---
title: "When to Clean Your Solar Panels: A Guide for Gauteng Homeowners"
description: How often should you clean solar panels in Johannesburg and Pretoria? The best months, the warning signs, the right time of day, and how to clean without voiding your warranty.
image: https://cleanvolts.co.za/hubfs/CleanVolts%20when%20to%20clean%20your%20solar%20panels.png
---

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# When to Clean Your Solar Panels: A Guide for Gauteng Homeowners

![Tony Lopes](https://cleanvolts.co.za/hs-fs/hubfs/clean%20volts%20launch%20post.png?width=48&height=48&name=clean%20volts%20launch%20post.png)

 Tony Lopes

September 29, 2026

## **The short answer**

If you live in Johannesburg, Pretoria or anywhere on the Highveld, plan to clean your panels twice a year: once in late winter or early spring (August to September), after the dry season and before the long summer days, and once in autumn (March to April), before the dry months start. Between those cleans, check your inverter app. If your output drops on clear days and you can see a film of dust or a few bird droppings, clean sooner.

That is the rule of thumb. The rest of this guide explains why the Highveld needs its own schedule, how to tell when your panels are due, and how to clean them without damaging the glass or your warranty.

## **Why panels on the Highveld get dirty on a schedule**

Gauteng has two seasons that matter for your panels.

**The wet season (roughly October to March).** Afternoon thunderstorms rinse loose dust off tilted panels every few days. Rain does not remove everything: bird droppings, pollen stuck to the glass and the grimy film that builds up near roads stay behind, and rainwater can leave its own spots as it dries. But during summer the build-up is slow.

**The dry season (roughly April to September).** Months can pass without meaningful rain. Dust from gardens, gravel roads, building sites and mine dumps settles on the glass and stays there. Winter veld fires add a fine layer of ash that can cover a whole suburb overnight. By August, most arrays have been collecting dirt for four or five months.

Spring adds one more source. When the jacarandas, oaks and other trees flower in September and October, pollen sticks to the glass, and on panels near trees it is often the most visible layer.

## **How much output does dirt cost you?**

Less than some cleaning companies suggest, but more than nothing. The International Energy Agency's research programme on solar power estimates that soiling costs solar systems worldwide around 3 to 5% of their annual energy. That is an average: dry, dusty sites lose more, and so do panels near construction, mining or busy roads.

For a sense of scale, a 5 kW home system in Johannesburg produces roughly 8,000 kWh a year. A 5% loss is about 400 kWh. At an illustrative tariff of R3.50 per kWh, that is around R1,400 a year of electricity you paid to generate and did not get. The loss is highest at the end of the dry season, which is why the August to September clean pays back the most.

Uneven dirt matters more than an even film. A single bird dropping over one cell blocks light to that cell while the cells around it keep working. The shaded cell can heat up (a "hot spot"), which lowers output and, over time, can damage the panel. Treat droppings as a reason to clean now rather than waiting for the next scheduled clean.

## **Signs your panels are due for a clean**

- **Your output has dropped on clear days.** Compare a cloudless day this month with a cloudless day at the same time last year, or with the days just after your last clean. A steady decline across several sunny weeks points to dirt. A sudden drop points to a fault, so call an installer rather than grabbing a hose.
- **You can see a film or streaks.** Look at the panels from the ground or a window in the early morning, when the low sun shows up dust.
- **There are bird droppings, leaves or pollen patches.** Anything that covers part of a panel rather than all of it.
- **There is a dirt line along the bottom edge.** Rainwater carries dust down to the frame and leaves it there. On panels tilted at less than about 10 degrees, water does not run off well and this line builds up quickly. Moss or lichen can start growing in it.
- **Something dusty has happened nearby.** Building work next door, a veld fire, road works or a dust storm.

## **A cleaning calendar for Gauteng**

| Months | What is happening | What to do |
| --- | --- | --- |
| January to February | Peak rain season. Storms rinse the panels regularly. | Check for bird droppings and leaves after storms. A full clean is rarely needed. |
| March to April | Rain tapers off. The dry season is about to start. | **Scheduled clean.** Start the dry months with clean glass. |
| May to July | Dry, dusty, veld fire season. Cold mornings, sometimes below freezing. | Watch your output. Spot-clean droppings. Clean only in the middle of the day, when the glass is above 5°C. |
| August to September | End of the dry season. Dust and ash at their worst. Pollen starts. | **Scheduled clean.** This is the clean that recovers the most output. |
| October to December | Storms return. Jacaranda and other pollen. | Check for pollen patches and droppings, especially on panels near trees. |

Adjust the schedule for where you live. Homes near mine dumps, farmland, gravel roads or a building site may need a clean every three to four months. Homes in leafy suburbs with steep roofs may get away with once a year plus spot-cleaning.

## **The best time of day to clean**

Clean when the panels are cool. On a summer afternoon the glass can be too hot to touch, and spraying cold water onto hot glass can crack it. Water also evaporates quickly on hot glass and leaves marks.

Module manufacturers set out the conditions in their cleaning instructions. JinkoSolar, one of the most common brands on South African roofs, recommends cleaning in the early morning or late afternoon, or on an overcast day, keeping the water within 10°C of the panel's temperature, and not cleaning at all when the air is below 5°C, because water can freeze on the glass.

On the Highveld that gives you two different windows:

- **Summer:** early morning, before the panels heat up, or late afternoon once they have cooled.
- **Winter:** mid-morning, once any frost has gone and the air has warmed above 5°C, but before the midday sun heats the glass.

## **How to clean without damaging the panels or your warranty**

Every panel manufacturer publishes cleaning instructions, and most warranties exclude damage caused by cleaning the wrong way. Check the manual for your panels. The rules below are common to most of them.

- **Use plain water.** No dishwashing liquid, window cleaner, solvents or household chemicals. They can damage the anti-reflective coating on the glass and can void the warranty. Water with a high mineral content leaves spots, so filtered or deionised water gives the best finish.
- **Use something soft.** A soft brush or sponge on an extension pole. Never a scourer, abrasive powder or anything that could scratch the glass.
- **Keep the pressure low.** A garden hose is fine. Jinko's guidance for a hose is to keep the pressure under 675 kPa, which is well below what a pressure washer produces. If you use a pressure washer at all, keep it on a wide spray and well away from the glass, the edges and the cable connections.
- **Never stand, kneel or lean on a panel.** The pressure can crack the cells inside the glass without leaving a visible mark.
- **Do not clean a damaged panel.** If you see cracked glass, burn marks or exposed wiring, stay away from it and call an installer. It can be a shock hazard.

## **Do it yourself, or call a professional?**

If your panels are on a single-storey roof and you can reach them from the ground with a pole and hose, cleaning them yourself is reasonable. Follow the rules above and never climb onto the roof to do it.

Call a professional if the panels are on a double-storey or steep roof, if reaching them means working on the roof, or if you want the system checked at the same time. Falls from roofs are a far bigger risk to you than dirty panels are to your electricity bill.

A good professional clean is also an inspection. While the panels are being cleaned, a technician can check for:

- cracked or discoloured panels
- loose or damaged cables and connectors
- pigeon nests under the panels, which are common in Gauteng and can damage cabling
- loose mounting clamps or rails
- hot spots, using a thermal camera, which show up faults you cannot see with the naked eye

## **Frequently asked questions**

### **Doesn't the rain clean my panels?**

Partly. Summer storms remove loose dust from tilted panels, but they do not shift bird droppings, stuck-on pollen or grime, and the Highveld goes months without rain in winter. Rain slows the build-up. It does not replace cleaning.

### **How often should I clean solar panels in Johannesburg?**

Twice a year for most homes: March to April and August to September. More often if you live near mining, farmland, gravel roads or construction.

### **Will cleaning my panels void the warranty?**

Cleaning will not. Cleaning the wrong way can. Chemicals, abrasive tools, high-pressure water and walking on panels are the usual causes of damage that manufacturers exclude. Check the cleaning section of your panel manual, or ask your installer.

### **Can I use dishwashing liquid?**

No. Most manufacturers say to use plain water only. Soap can leave a residue that attracts more dust and can damage the glass coating.

### **Should I switch the system off before cleaning?**

Panels produce electricity whenever light falls on them, so switching off the inverter does not make them "dead". It is still good practice to follow your installer's shutdown procedure before cleaning, and to keep water away from the inverter, cables and connectors.

## **Book a clean**

CleanVolts cleans solar panels across northern Johannesburg with deionised water and soft brushes, following your panel manufacturer's instructions. We take a performance reading before and after, so you can see exactly what the clean was worth. The best time to book is August to September, at the end of the dry season.

[**See our solar panel cleaning service**](https://cleanvolts.co.za/solar-panel-cleaning)

## **Sources**

- [IEA PVPS: Soiling Losses, Impact on the Performance of Photovoltaic Power Plants](https://iea-pvps.org/key-topics/soiling-losses-impact-on-the-performance-of-photovoltaic-power-plants/)
- [JinkoSolar Global Installation Manual (2024)](https://www.jinkosolar.com/uploads/JinkoSolar%20Global%20Installation%20Manual_20240814_A1.pdf)
- [JinkoSolar Photovoltaic Modules Cleaning Manual](https://manuals.plus/jinko-solar/photovoltaic-modules-manual-5)

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