When cleaning genuinely pays
The value of cleaning is the production you recover, and that depends entirely on how dirty the array actually gets.
- Long dry seasons. Months without rain let soiling accumulate steadily with nothing to remove it.
- Agricultural or construction dust. Persistent particulate that bonds to glass rather than blowing off.
- Heavy pollen. Seasonal, sticky and genuinely obstructive.
- Bird roosting. Droppings are opaque and do not wash off easily. This is the one case where cleaning is almost always justified.
- Low-slope arrays. Below roughly ten degrees, water sheets rather than runs and carries much less away.
When it does not
A pitched array in a climate with regular rainfall, away from farmland and major roads, with no birds roosting on it, is mostly cleaning itself.
In those conditions a paid cleaning recovers a small fraction of annual production, and the recovery decays as soiling returns. The arithmetic rarely favours it.
This is not a popular thing for a solar site to say, which is roughly why it is worth saying.
Partial shading is not soiling
One dramatically underperforming string is far more often shade, a failed optimiser or a bad connection than dirt.
Uniform soiling reduces everything a little. A sharp drop on part of the array is an electrical or shading problem, and cleaning it will not help.
Method, and the part that actually matters
Water, a soft brush, and nothing abrasive. No pressure washers, which can force water past module seals and void warranties. No detergents unless the manufacturer permits them. Cool panels, early morning — cold water on hot glass is a thermal shock risk.
The part that actually matters: do it from the ground with an extension pole, or pay someone with proper fall protection. Roof falls during casual maintenance are how this goes badly wrong.
How the work runs
- Check the data firstCompare current production against the same period last year. If there is no gap, there is no problem to solve.
- Rule out the alternativesShade, a failed optimiser or an inverter fault look like soiling in the monthly totals and are not.
- Decide if you are in a soiling conditionDry season, dust source, pollen, birds, or a low-slope array. If none apply, rain is doing the job.
- Choose the methodGround-level pole and water where reachable; a professional with fall protection where not.
- Measure afterwardsCompare a clear day before against a clear day after. This tells you whether to ever do it again.
What moves the price
We do not publish a national average and present it as your price. These are the variables that separate two quotes for the same job — run your own numbers with the cost guides and calculators, and check what incentives you actually qualify for.
| Factor | Why it moves the number |
|---|---|
| Roof access | Single-storey and walkable is cheap. Two storeys, steep pitch or tile is not. |
| Array size | Priced per panel or per visit depending on the company. |
| Frequency | Annual contracts cost less per visit and are worth it only if you are genuinely in a soiling condition. |
| Bird proofing | Mesh or deterrents around the array are a separate job, and usually a better investment than repeat cleaning. |
What to ask before you commit
Take this list to the conversation. A professional who answers these directly is telling you a lot; one who deflects is telling you more.
- What production gain should I expect, and how will we measure it?
- What method and what water do you use — and do you use pressure washers?
- Do you carry liability cover for roof work on my property?
- Have you checked whether this is soiling or shading before quoting a clean?
- Would bird proofing be better value than a cleaning schedule?
Common questions
Do solar panels need cleaning?
In most climates with regular rainfall and a pitched array, not really — rain does most of the work. Cleaning matters in long dry seasons, near dust sources, under heavy pollen, where birds roost, and on near-flat arrays.
Can I clean my solar panels myself?
From the ground with a soft brush and an extension pole, yes. Climbing on the roof is not advisable, and pressure washers can force water past module seals and void the warranty.
How often should panels be cleaned?
Only as often as your own production data justifies. Measure a clear day before and after a clean; if the difference is negligible, that is your answer.
My production dropped sharply — is it dirt?
A sharp drop is usually shading, a failed optimiser or microinverter, or an inverter fault. Soiling reduces output gradually and fairly evenly across the array.