How to Clean Solar Panels – Tips for Keeping Panels Clean

Since owning and running a renewable energy company – Squeaky Energy, I’m often asked how to clean solar panels, especially with having so many of them in our solar farms. It is reasonable to assume that solar panels can lose 15-25% of their efficiency if not cleaned properly.

I don’t think there is any perfect way to clean solar panels, but we’ve put together our own method that our maintenance guys use to keep all of our solar panels clean across our entire fleet, ensuring that they keep generating at optimal output, as even just 20% reduction in output (because of dirt etc) you could potentially be losing £80-120 ($60-$95) per year*

Why Clean Solar Panels?

  • Increase the amount of energy they could generate
  • By cleaning them, you are also inspecting them, looking for damage/wear and tear
  • Give the panels longer life

Items to Buy

We’ve tried lots of different weird and wonderful solar panel cleaning systems, many broke after a while, others were simply not up to the job and others just worn out, so we’ve settled on the following list based on many success and failures! (click each link to buy the item)

Water Fed Window Cleaning Pole – A great addition to your Solar Panel cleaning kit, you simply attach a hosepipe to the end of it, and it has a brush/squeegee at one end and it’s extendable to 2.1m (17ft) while being able to mix the soap with the incoming water at the head  

Fairy Platinum Washing up Liquid – Simple, biodegradable and inexpensive, works a treat and does not damage or rot the panels

Metal Bristle Weed Brush – If the metal edges of the Solar Panels are caked in layers of bird droppings, moss etc, use this to get rid of it. With some of the ones we’ve purchased we’ve cut the wooden handle down to size using a hacksaw making it easier manage on the roof…

 

 

How to Clean Solar Panels

So…I thought I would share our “secrets” with you.  Firstly, please ensure you have safe access the panels as if they are on a roof, accessing them could be dangerous:

  1. Turn off the supply to the solar panels, it is a possibility you could get a nasty shock or at least help to “ground” out the panels, so stay safe and turn them off first by turning off the DC isolator on the inverter, then turning off the AC isolator which feeds it.
  2. Rinse the panels with cold water using a hosepipe first, so any dirt or residue that is stuck on them can be wiped off easily. If the sun is shining, this will help cool the panels down so expect to see a little steam
  3. Mix some washing up liquid with warm water in a bucket, and with a soft brush head begin cleaning the panels one by one (in straight lines from top to bottom) or better still buy the window cleaning pole that we use and pour the washing up liquid into the soap dispenser before you start.
  4. Rinse the panels once cleaned with the hosepipe
  5. Use the squeegee to follow the same pattern to remove any excess water so the panels dry without any soap left on them

 

How Often Should you Clean Your Solar Panels?

At Squeaky Energy, in the UK, we clean our panels twice every year:

March – To clear dirt and pollution from the winter months and prepare for the peak generation period (summer)

Sept – To clear any dirt, bird droppings (increased activity during mating seasons) etc that have accumulated over the summer period

If your roof is prone to dust, leaf or bird droppings, cleaning your panels regularly is a good idea. The more dirt there is covering your panels, the less energy output they’ll deliver (In fact, a study conducted at Google’s 1.6MW solar farm in Mountain View California, found dirty panels could suffer from decreased energy output of up to 25%)

 

Is it Worth Doing?/What About the Cost

The decision to clean your solar panels depends on five key things:

  • Location (does it rain regularly or only during certain months) 
  • Tilt Angle of your panels (steeped panels (20+ degrees) tends to stay much cleaner)
  • The amount of wind blown dust (Southern Europe, North Africa, etc, where the rainfall is quite low and airborne dust high)
  • Your electricity/incentive rate (feed in tariff in the UK)
  • Cost to clean your panels

Having been asked the question “is the labour cost worth the extra generation (if any) of cleaning?” –  Yes I think it is, as while cleaning my cleaners are doing annual inspections and will report back any issues like broken/loose panels, fixings or others, so there is a greater value here.

Obviously I’m talking about a commercial operation, but if you are a homeowner and can clean them yourself at a little cost then it will be a job worth doing and if roof based, why not clean your solar panels while you are cleaning your gutters?

You can read some Analysis of dust losses in solar panels here

Other things to watch out for

  • Always use a biodegradable cleaner
  • Panels that are tilted at about 5 degrees or less may get debris or a small puddle of water/dirt accumulating along the lower row of cells, if the panel cannot be titled anymore, you may need to clean your panels more often
  • Remember that you should never put pressure on the panels by stepping or putting weight on them.
  • Never use anything abrasive, sharp or any type of brush that would cause scratching on the panels
  • Panels should not be cleaned with a pressure washer, as doing so could result in cracked glass

Here are the products we used:

 

 

Update: If you are an owner of solar panels and use them at home, you might be interested in my Review of the ImmerSun: Is Self Consumption the Future?

Anyway, I hope that helps, but as always, I appreciate any comments and tips from others in the comments below.

 

 

*Based on average size of panel being 285w 3400kwh (energy savings trust)