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Solar panels are amazing! They supply clean and renewable power to your home without having to worry about high electricity bills.

Once the solar array is up on the roof, we seldom think about them... until we see that power output is down.

This is the time we begin to wonder whether it is time the solar panels need washing!

Clean solar panels are essential in order to maximize power production. Dirt, dust, bird droppings, dead leaves and other debris can cover the panels and bring power production down.  This is why it is important to clean your solar panels regularly.

Is it alright to clean solar panels using a pressure washer?

The answer to this question is: it depends!

Using a pressure washer to clean your array on the roof means that you can just blast on the water without having to use other tools, since the pressure is usually enough to get rid of dirt and debris.

However, too much power can cause the seals around the cells to break and allow water and humidity to enter. While this won't happen immediately, the leaks could become bigger over time and cause your panels to fail.

Does rain count as cleaning?

Yes, rain counts as cleaning... but not all the time!

Gentle drizzles and rain showers can get rid of some dirt and dust from your solar panels. But this is still not the same as washing them. A build up of bird mess and dried leaves can stick to a solar panel and a small amount of rain won't be able to wash it off.

According to researchers at the National Renewable Energy Laboratory, the amount of energy loss from a solar panel due to dust and general soiling, can be as high as 7%. While many homeowners can live with this, long periods of zero rainfall can cause up to 20% energy loss daily.

This means if you live in an area with a dry climate like Southern California, your solar panels could soon become inefficient due to buildup of dirt and grime.

In order to clean your rooftop panels decently, you need a 20-30 minute thunderstorm or heavy rain. This should be enough to soften bird poop and stubborn grime. But it's still better to do the job by hand so that you can inspect every cell and ensure that you have clean solar panels.

How to clean solar panels using a pressure washer

No Moss Solar Panel Cleaning sacramento elk grove

As we said before, cleaning your solar panels using direct pressure can damage your solar array. However, this does not mean to say that you should keep your pressure washer in your shed! 

You can still use your washer just as long as you don't point it directly to the cells or use heavy power during the cleaning.

Materials/Tools

Aside from a pressure washer, you'll want some of these things for solar panel cleaning

  • Bucket
  • Mild detergent
  • Microfiber squeegee and scrubber, soft cloth or sponge
  • Tap water and hose
  • Extension pole
  • Soft brush

Safety First!

solar systems are installed on the homeowner's rooftop

Most solar systems are installed on the homeowner's rooftop. This means that solar panel cleaning can be risky. Having safety precautions can reduce the risk and make sure that you finish the solar panel cleaning successfully.

Some suggested safety precautions before cleaning your solar panels:

  • Follow the procedure in the manual on how to shut off solar panels properly
  • Make sure that the roof is strong enough to bear your weight
  • Use a sturdy ladder to climb up to your roof
  • Consider a safety harness if your panels are installed on a tilted surface
  • Wear boots with non-skid soles to avoid slips and falls
  • Avoid cleaning your panels during a rainstorm, rainy day or cloudy day. Your panels should also be dry before attempting to clean them
  • Have a first aid kit and a family member with a cellular phone on standby while you clean your solar panels.

Step-by-step Instructions

Cleaning solar panels is just like cleaning your car windshield or house windows!

Here is a basic guide on how you can use a pressure washer to clean your solar panels.

  • Mix an appropriate amount of  soap and water in your bucket.
  • Start cleaning from the top most panel going downwards. This way, water and debris will fall on dirty panels and you won't have to repeat the whole cleaning process.
  • Remove dust and debris using a soft brush. Focus on the bottom part of each frame and around the corners since this area is where stubborn grime and dust settle.
  • Once all of the debris build up has been brushed away, you can use a pressure washer to wet the panels. Make sure not to point directly on the panel! Point the nozzle upwards instead to create a rainfall to wet the solar panels.
  • Apply the soap mixture on the panels.
  • Use a microfiber squeegee on an extension pole to gently scrub the panels. You could also use a soft cloth or a sponge to scrub the panels but an extension pole will make your job easier since you don't have to reach too high.
  • Rinse the solar panels with water.
  • Inspect panels to make sure that they are dirt and debris-free. If not, repeat soaping and scrubbing on areas that need more cleaning.
  • A garden hose can also be used to clean your solar panels.

Some people ask whether it is alright to use laundry detergents on solar panels instead of liquid soap. Laundry detergents tend to leave a thin soapy film on the panels which can reduce efficiency. You could add vinegar to your soapy mixture to reduce the amount of bubbling and film production if you decide to use detergent.

Companies selling solar panels or installation companies will also recommend suitable cleaning methods and products when you buy the system.

Whatever cleaning method you use to clean your solar panels, the basics we describe above remain the same.

And remember - regular solar panel cleaning can boost energy production and maintain your solar panel's efficiency!

Technician cleaning rooftop solar panels

How to deal with stubborn dirt

Do not use abrasives to get rid of stubborn dirt!

You can opt to repeat soaping and light scrubbing on the dirty area with a soft cloth or sponge, or you can use a cleaning liquid to get rid of the dirt. 

Just make sure that everything you use to clean panels is soft and mild.

How to deal with bird droppings

The cleaning method for bird poop on your solar panels is to use soapy water and a soft cloth. 

Start by using water to wet the area. Apply soapy water on the surface and use a soft cloth to scrub it away. Repeat the process until all of the poop is gone.

How to deal with oily stains

Oily stains usually happen when you live near an airport or downwind from a busy road where trucks pass by all the time. 

For oily stains, you can use isopropyl alcohol to spot clean areas of your solar system.

When to seek professional help

Many homeowners opt to clean their solar panels themselves rather than hiring a professional cleaning company. Whenever you clean your panels, remember that it is best to do so from the ground whenever possible.

However, most solar system arrays are on rooftops so if you think that there is significant risk involved, call a solar cleaning company to come help keep your power generation high and electricity bills low.

You can write off the expense of hiring a professional company through the money you saved on energy bills!

Best Time to Clean Your Solar Panels

Best Time to Clean Your Solar Panels

The best time to clean your solar panels is early morning, early evening or on overcast days. Avoid cleaning during bright sunny days because water will dry up quickly causing water spots.

Cleaning your panels when the sun is low on the horizon or when it's cloudy is also easier for you as it is cooler.

How often do you need to clean solar panels?

In order to maximize the financial benefits of solar panels and keep up energy production, you need to clean your solar panels regularly. How often your panel needs cleaning depends on location: is it windy? Are there lots of birds or trees?

For instance, living in an area where there are lots of birds mean that your roof is going to see a lot of poop. When there is a lot of poop, areas of your panels will get obscured and your system efficiency will go down. The same is true if your rooftop gets a lot of dust or leaves falling on it.

If you live in this type of area, we recommend regular monitoring of your solar system to ensure that they are still efficient, and to clean them regularly.

A thorough or professional cleaning once a year can boost energy production compared to just cleaning by rainfall.

Monitoring system

Monitor your solar system's functionality and your energy bills month to month. When you start to see spikes in your bills, check your monitoring system for solar power generation and efficiency.

If your solar system efficiency is down and electricity bills are up, then you probably need to clean your solar panels ASAP!

Wrap up

A higher energy bill is generally the result of dirty solar panels, which produce less electricity. Cleaning solar panels can be tiring but it is part of protecting your investment.

Clean solar panels can ensure that energy production remains high, and remember: you don't need to use expensive products to clean your solar system. Good old fashioned water, soap and a soft cloth is enough to do the trick!