Dust and pollen can cut output by a few percent. That does not sound like much, and on any single day it is not. But San Diego summers can go weeks without a drop of rain, and in that stretch a thin film builds up on every panel in the county. Add pollen in the spring, a breezy afternoon of dust from nearby construction, maybe a few gifts from the local birds, and that small loss starts to show in your monitoring app.
Cleaning is easy if you do it right. Do it wrong, though, and you can scratch the glass, void part of a warranty or put yourself at risk on a ladder. Here is the method our service crew recommends to every homeowner, along with the cases where it is better to call us instead.
Do your panels actually need cleaning?
Many homeowners never clean their panels, and their systems run just fine. Winter rains in Southern California usually rinse the glass naturally, and most panels are tilted enough for water to wash dirt away. The question is not whether panels get dusty. They always do. The question is whether the dust is costing you enough power to bother.
A few situations make cleaning more worthwhile. Homes near unpaved roads, farms, freeways or active construction sites collect more grime. Panels with a very low tilt hold onto dirt longer. Homes under trees catch pollen, sap and leaves. And houses close to the ocean can build up a light salt film that attracts more dust.
Watch your monitoring app — it tells you when it’s time.
Marco
Marco, who leads our installation and service crews, prefers data over guesswork. Your monitoring app shows how much power your system makes each day. Compare a clear, sunny day this month to a similar day a few weeks after the last rain or cleaning. If production has slipped noticeably and the weather and season do not explain it, dirty glass is a likely suspect. If the numbers look normal, you can probably leave the hose coiled.
Early morning
Rinse with a hose before the panels heat up. Cold water on hot glass is a bad idea. By late morning on a summer day, panel glass can get very hot to the touch. Spraying cool water onto hot tempered glass creates a sudden temperature change, which puts stress on the glass and the frame. It is also simply less effective, because water evaporates quickly on a hot surface and leaves spots behind.
Early morning is ideal for several reasons. The panels are cool from the night. There is often a light dew on the glass that has already started to loosen the dust. The water will not evaporate before it runs off. And you will be finished before the hottest part of the day, which is better for you, too. A cloudy, cool afternoon can also work.
Stay on the ground
Do not climb onto the roof to clean panels. Wet glass and wet shingles are slippery, and falls from roofs are serious. For most single-story homes, a garden hose with a gentle spray nozzle and a long extension pole can reach the panels from the ground. If your panels are on a second story or a steep roof, or you cannot reach them safely from the ground, it is time to call a professional.
Skip the soap
Plain water and a soft brush on a pole is all you need. Solar panels have a smooth glass surface, and many have special coatings that help them shed dirt and absorb more light. Harsh cleaners, soaps that leave residue and anything abrasive can damage those coatings or leave a film that attracts even more dust.
What to use and what to avoid
- Use a garden hose with a gentle, wide spray setting
- Use a soft brush or sponge made for glass on an extension pole
- Use filtered or deionized water if your tap water leaves heavy spots
- Avoid pressure washers, which can force water into seals and damage the surface
- Avoid household glass cleaners, dish soap and anything with ammonia
- Avoid scrub pads, steel wool or stiff bristles
Before you buy anything, check your panel manufacturer’s care instructions. Some warranties have specific rules about cleaning methods, and following them protects your coverage. If you are unsure, call us and we will look up your panel model.
A simple cleaning routine
- Check your monitoring app and pick a cool morning after a long dry stretch
- Turn the hose to a gentle spray and rinse the panels from the ground, top to bottom
- If dirt remains, use a soft brush on a pole with plain water and light strokes
- Rinse again to carry away the loosened dirt
- Let the panels air-dry and compare production over the next few sunny days
You do not need to shut the system off to rinse it from the ground with a hose. The panels are designed to be rained on. Never touch wiring, connectors or anything under the panels, and do not spray directly into the inverter or electrical boxes.
Key takeaway: clean only when the app says it is worth it, do it on a cool morning from the ground and stick to plain water and a soft brush.
Birds, sap and other stubborn spots
Dust rinses off easily. Bird droppings and tree sap are another story. They stick hard, and even a small spot can shade part of a panel enough to lower the output of the whole row. Soak the spot with water for a few minutes before brushing gently. Do not scrape. If droppings are a regular problem, pigeons may be nesting underneath the panels, which can damage wiring and create a mess. We install critter guards, a wire mesh around the edges of the array, to keep birds and other animals out.
Leaves and debris that collect along the bottom edge of the panels should also be removed, since they trap moisture and dirt. Trimming nearby trees helps on both counts and reduces shade at the same time.
Keep an eye out for anything that is not dirt. While you are rinsing, look for cracked glass, panels that seem to have shifted, loose wires hanging below the array or scorch marks near connectors. Do not touch any of these. Take a photo from the ground and send it to us so a technician can take a closer look safely.
When to call the pros
Professional cleaning makes sense when your panels are hard to reach, when your home is in a particularly dusty spot or when you simply would rather not deal with it. Our service visit includes a gentle cleaning with purified water, a visual inspection of the mounts and wiring and a quick check of your system’s performance data. Many homeowners schedule one visit a year near the end of summer, before the fall winds pick up.
If your production drops sharply and cleaning does not bring it back, that is a sign something else may be going on, like a faulty connection or an inverter issue. Give us a call. Your system is designed to work for decades, and a quick check now keeps it running at its best through every dusty summer ahead.
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