Tip of the Week

How to Clean Your Solar Panels

Written by Fast Window Cleaning on 17-Nov-2015, in categories: Tips


Solar panels mix modern, sleek design with fixed parts, making them pretty easy to be cared for and in rare need of repair.

Even so, there is one kind of maintenance work that should be considered, solar panel cleaning.

This way you can help maximize their efficiency and, in turn, generate more power.

Leaves, pollen, airborne particles from dirt as well as bird poop and other types of debris can land on your solar panels (due to their upwards angle, the build-up of debris will not wash off with just rain). Dirty panels translate into power loss because the grime and debris reduces the ability of the solar array to perform at maximum capacity.


Solar arrays are made up of a number of solar modules wired together, with each solar module made of solar cells mounted collectively in a frame. These solar cells are made of semiconductor materials with one side positive and the other negative.

When the sunlight reaches a solar cells it excites the electrons in the semiconductor material. This way, the energy of the sunlight can be captured and transformed into electricity.  If the cells are dirty, less sunlight will be absorbed and less electricity will be generated.

There are recent studies that focus on the cost-effectiveness of solar panel cleaning. These studies claim that it’s not really worth it because the energy-loss is close to insignificant for domestic buildings. The major issue with these studies is that they were conducted in the US – San Diego Area.

The difference between the UK climate and the US one is significant and it greatly impacts this subject.

Rainfall quantities are comparable in San Diego and London for the months of January, February and March but then there is a considerable drop off in precipitations in San Diego. This is why comparing the 2 climates is unfair. (Source: http://www.world-climates.com/)

This specific study was conducted on a residential arrays for a period of almost 6 months.

The conclusion was that the panels lost 7,4% of their efficiency in those 6 months, which roughly translates to  £30

At the same time, the tests shown that it takes time for a layer of dust to cover a surface but when it’s already present, it attracts dust particles at an increased rate. If the study would’ve been extended the percentage of loss would double with the arrays losing over 15% over the course of a year. Money-wise, this translates to over  £ 100 loss.

The research shows that panels would lose about 0.05% output each day so if you skip cleaning your solar panels for 2 years you could be losing 36,5% of your electricity generation.


It’s usually recommended to clean them 2 times/ year, in early spring and late summer, before the rainy season starts again.

For more customized recommendations you should check with the manufacturer.

Keep in mind that if you live in an area with lots of trees that lose leave in the fall, you’ll have to remove those in order to avoid accumulating debris. Also, in the winter time, you might have to occasionally sweep off snow if it’s not melting by itself.


  1. DIY
  2. Use a Cleaning Robot
  3. Solar Panel Cleaning Services


So, let’s start with the first:

   1. DIY Solar Panel Cleaning


Before starting to clean your solar panels you should check your manufacturer’s specific cleaning recommendations.

Usually you can rinse off the panels by using a garden hose while standing on the ground. If the solar panels are covered with debris or dirt you’ll have to climb up your roof to make sure you clean them properly.

It’s best to schedule the cleaning in a cooler time of the day because the panels can get extremely hot after being in full sunlight.

Most important thing: follow the instructions for turning off the panels! NEVER get up on the roof next to high-voltage wiring if the power is not off.

The actual cleaning is similar to washing a window, you can fill a bucket or a spray bottle with warm soapy water, wipe off the panels and let them air-dry or dry them off with a cloth.

In addition you can use nano-cleaning products that will stretch the time between cleanings. These products work with the rain water, letting it do most of the cleaning for you.

You have to keep in mind that rainwater by itself won’t properly clean your panels. The grime will accumulate and attract airborne particles that will attach to the surface after the rainwater evaporates and in the end the panels will get dirtier than before they were before the rain.


   2. Use a cleaning robot or an automatic cleaning system


This option requires an investment into a an automatic solar panel cleaning system or the use of a robot that functions similar to those used to clean swimming pools.

These usually work by attaching nozzles to your solar panels.The system will be connected to and existing hose bib or plumbed in and it also requires a power supply in order to operate the controller. After the installation you just have to program the system and occasionally refill the soap concentrate and replace the water filters.

This options comes at the cost of a serious investment.

   3. Solar Panel Cleaning Services


Your third option (the most practical one) is to simply outsource this job to a professional solar panel cleaning company in London.

This way you know you’ll have your solar panels carefully cleaned, without all the hassle.

We’ve been doing this for well over 17 years and we only use top of the range cleaning kits and products. We clean them safely, using a water-fed pole system that can reach your roof from the ground with  a soft head brush attachment so we won’t cause any damage (we don’t use the squeegee method in order to avoid streaking).

The water is purified and de-ionized and it contains no chemicals or detergents. This way we makes sure there won’t be any sticky residue left, therefore nothing for the dust to adhere to.

The telescopic poles with soft brush heads will do the cleaning while not applying much pressure because we know that the panels are quite fragile. By not using chemicals or detergents we offer a risk-free cleaning.

For more information – you can request a Free quote here.