Yes, it can. Dust, pollen, ash and droppings sit on the glass and block some of the sunlight that would reach the cells, so removing that layer lets more light through. How much you gain depends on how dirty the panels were and what else is going on with your system. A heavily soiled array has more to gain than a lightly dusty one, and some problems can’t be fixed with a cleaning at all.
Here’s how to think about it and how to check your own numbers.
How does dirt reduce solar production?
Solar cells make power from light. Anything between the sun and the cell takes some of that light away. A thin, even layer of dust does a little. A layer of pollen, a film of road grime or a patch of droppings does more. Because cells in a panel are wired together, a dirty spot over a few cells can pull down more of the panel than the spot itself covers.
That’s why a few droppings in the wrong place can matter more than an even coat of dust. Dirt concentrated on one part of a panel can matter more than an even coat. That’s one reason we remove droppings carefully by hand instead of rinsing and moving on. It’s also why dirt along the bottom edge, where water collects and dries, is worth a close look.
What changes how much cleaning helps?
Several things decide it.
| What varies | How it affects the result |
|---|---|
| How dirty the panels were | Heavier soiling means more to gain |
| Tilt | Flatter arrays hold on to more dirt |
| Season and rain | A long dry stretch means more buildup |
| Surroundings | Trees, dust sources and birds add more |
| System design | Layout and wiring change how sensitive the array is to local shading |
| Time since the last cleaning | Panels cleaned recently have less to gain |
That last row matters. If you’ve been on a schedule, the gain from any one visit is smaller because the panels never got very dirty. If it’s been years, you have more to see.
What do customers see?
Customers tell us they see up to 32% more output after a cleaning. That’s what they report to us. It isn’t a promise and it isn’t a number for every system. A lightly dusty array on a steep roof may show very little change. A neglected array under a tree or near a construction site may show more.
How can I check before and after with my app?
Your monitoring app is the best tool for this. The trick is comparing like with like.
- Before the cleaning, note the daily production for several clear, sunny days in a row.
- Note the date of the cleaning.
- After the cleaning, pick several clear, sunny days with similar temperatures and season.
- Compare the two sets. Don’t compare single days.
Avoid comparing a sunny day to a hazy one, or a day in April to a day in July. The sun’s angle and the day’s length change over the year, and hot panels make a little less power than cool ones. Those changes can be bigger than the effect of the cleaning, so keep the dates close together. If you can, look at the peak-hour numbers as well as the total.
For how often to check, see how often to clean solar panels.
Why do two homes get different results?
Because no two systems are the same. Two houses in Northridge might have the same number of panels, but one sits under a eucalyptus and the other doesn’t. One was cleaned in spring and the other hasn’t been touched in three years. One has a tilted array and the other is nearly flat. Add different inverters and different weather on the days compared, and you’ll get different numbers.
Coastal and inland homes differ as well. Near the coast, the marine layer burns off later in the morning, which affects how you read morning production. Inland homes in Simi Valley or Saugus deal with hot, dry, dusty summers.
Why isn’t a gain guaranteed?
Because we can’t see inside your system, and because dirt isn’t always the main problem. If your panels were fairly clean, there’s little to remove. We’d rather tell you that than promise a number. Our guarantee is about the work: if you’re not satisfied, we’ll come back and make it right at no additional cost.
What can cleaning not fix?
Cleaning only removes what’s on the glass. It won’t help with:
- Shade from a tree, a chimney, a neighbor’s roof or a new building
- A failing or misconfigured inverter
- Slow, normal degradation of the panels over the years
- A cracked panel or damaged cells
- Loose or damaged wiring
- A monitoring app that’s reporting wrong or has lost its connection
We don’t repair or inspect electrical equipment, so if the numbers look off after a cleaning, call your installer or the equipment manufacturer. If we notice a cracked panel or a nest while we’re on the roof, we’ll tell you.
If birds keep coming back and dirtying the glass, bird proofing with humane mesh, spikes or netting can help keep the panels cleaner between visits.
Is it worth cleaning if I only see a small change?
That depends on what you care about. Some people clean for the production numbers. Others do it to keep droppings, pollen and mineral film from baking onto the glass year after year. A film that sits for a long time is harder to remove than one that’s cleaned regularly. A routine visit also gives someone a look at the roof, and we’ll tell you if we see a cracked panel, loose wiring or a nest under the array.
If the change is small, that’s useful information too. It tells you the panels weren’t the problem, and the next place to look is shading, the inverter or the age of the system.
What should I do if production looks low and cleaning didn’t help?
Start with your monitoring app. See whether the drop is across the whole array or only on a few panels, and whether it started suddenly or slowly. Then call your installer or the equipment manufacturer with those details. They can check the electrical side, which we don’t do.
Should I track production over a longer period?
Yes, if you’re curious. One before-and-after comparison tells you something, but a year of notes tells you more. Mark each cleaning on a calendar, glance at the app now and then, and see how quickly production drifts down between visits. Over time you’ll learn how fast your own roof gets dirty, whether it’s a tree, a dirt lot or the dry summer, and you can set a schedule that fits instead of guessing.
A note on warranties
Check your installer’s or panel manufacturer’s cleaning guidance before you book anything. It’s worth knowing what they recommend for your equipment. We use soft brushes and purified water, with no high-pressure washing on panels.
Cost and next steps
Cost depends on panel count, roof access and buildup, as explained in what changes the price of solar panel cleaning. We clean homes in Chatsworth, Tarzana, Thousand Oaks and across the valleys. Read about solar panel cleaning, see every area we cover, or call (818) 913-1626, Monday through Saturday, 7am to 7pm.