Just like anything exposed to the elements, your solar panels get dirty over time. Substances like dirt, debris, bird droppings, pollens, and pollutants can all accumulate on your panels, making it necessary for them to be periodically cleaned. If not, your solar system's efficiency can be compromised. Read on to learn how to clean your solar panels, and discover when it's appropriate to call a professional instead.
Before You Begin
Cleaning your solar panels involves spraying them down with a garden hose, but certain types of water should be avoided. If your water source has a high mineral content (hard water), it can leave behind a residue of mineral deposits that can inhibit the efficiency of your panels. Hard water is more common in homes supplied with well water, but this applies to some municipal water sources as well. When this is the case, consider using a deionizer or demineralizer attachment on your garden hose.
Another common source of residue is using conventional cleaning solutions, like dish soap. Many professional only recommend using plain water or a designated solar panel cleaning solution for cleaning panels.
Finally, avoid using a pressure washer to clean your panels, since the excessive pressure can damage the glass and electrical components. The pressure from your garden hose should be more than enough to thoroughly clean your solar panels.
Even though you shouldn’t be interacting with live electricity while you're cleaning the panels, shutting the power off to your solar system will eliminate the risk of electrocution. Follow the instructions provided by the manufacturer of your solar panels for the correct shut-off procedure.
If your solar panels are located on the roof of your home, try spraying the panels off with a garden hose from the ground first. This may be all that's required to clean a light layer of loose dirt and debris from your panels. If this isn't possible, ensure that you take the proper safety measures while working on the roof. These include:
- Working with a partner to stabilize your ladder, hand you materials, and call for help in the event of an emergency.
- Using an extension ladder with a ladder stabilizer (or ladder jack) with the top rungs three feet above the gutters. Do not use an A-frame ladder, as they are more prone to destabilize.
- Using a safety harness.
However, if your roof is unsafe to operate on, or you're uncomfortable working on it, consider hiring a professional instead. For more details on when this might be necessary, see When to Call a Professional, below.
How Often to Clean Solar Panels
It's generally recommended to clean your panels at least once a year, but possibly more often depending on the following factors:
- The panel’s pitch. Panels that lie flat tend to get considerably dirtier than those with a pitch of at least 5 degrees.
- The amount of rainfall your area experiences. Most panels are adequately cleaned from occasional rainfall. The absence of rain—as in dry climates or during summer—will cause more sediment to accumulate.
- Proximity to pollution sources. The airborne contaminants emitted from busy roadways and industrial settings may accumulate on your panels.
- Presence of trees above the panels. Trees can drop leaves on your panels and block the sun's rays, but they also attract birds that can leave droppings on the panels.
If done during the hot summer months, the panels should be cleaned in the early morning or late evening when the temperatures are lowest. Personal comfort aside, spraying the panels with water when they're hot can cause the panel's glass to break.
Equipment / Tools
- Garden hose with spray nozzle attachment
- Soft bristle brush
- Window squeegee
- Clean rag
- Bucket (optional)
- Extendable handle for bristle brush and/or squeegee (optional)
- Demineralizer or deionizer garden attachment for garden hose (optional)
- Extension ladder with ladder stabilizer (optional)
- Safety harness (optional)
- Solar panel cleaning solution (optional)
Rinse the Panel
Spray the entire surface of the solar panel with a garden hose to rinse off loose dirt and debris and to loosen up hardened residue. This will help prepare the surface for scrubbing.
Scrub the Panel
If using a solar panel cleaner, pour the recommended amount of solution into a bucket of water and dip the brush into the bucket prior to scrubbing. Otherwise, the water from the initial rinsing can be used.
Scrub one panel at a time, ensuring that you cover the entire surface. Using an extendable handle on the brush can make it easier to achieve comprehensive coverage, especially on larger panels. Spend extra time scrubbing areas with hardened residue such as bird droppings and pollen buildup.
Horizontally scrub the the outside edges where dirt tends to accumulate. This technique is called flossing. On tilted panels, concentrate on the bottom edge. Floss all four edges on flat panels.
Avoid making contact with wiring harnesses or cables underneath or on the side of the panels. Although the panels should be disconnected from electricity, accidentally hitting the panel's electrical components may damage them.
Use your garden hose to rinse the panel off one last time to remove the dirt or soap residue from scrubbing.
For tilted panels, place the head of the squeegee on the top end of the panel. Apply light to moderate pressure, and maintain that pressure as you draw the squeegee down to the bottom of the panel. Once you reach the bottom, start again at the top, but move the squeegee just to the side of where you just cleaned. Wipe off the residual moisture collected at the bottom with a rag.
For flat panels, use the exact same technique, but you can begin at any end. You should wipe off the residual moisture after each pass with the squeegee to prevent the water from running back onto the panel.
Just like the scrubbing procedure, attaching an extendable handle to the squeegee can help to achieve full coverage of the panel.
Repeat Steps as Needed
Visually inspect the panels to verify that they're clean. If not, repeat steps 1 through 3 as needed.
When to Call a Professional
If your solar panels on located on your roof, call a professional when:
- You aren't comfortable with, or capable of, working on your roof
- You don't have the appropriate safety equipment to work on your roof
- Your roof is heavily sloped
- There isn't enough room to safely maneuver around your solar panels