Frequently Asked Questions

Do you need to clean your solar panels?

Yes, you do need to clean your solar panels. As much as we’d love for solar panels to be truly maintenance-free after installation, the truth is they do need to be cleaned if you want to get the most out of your investment. If your solar panels are not cleaned regularly, dust, pollution, pollen, and other debris will accumulate on the surface of the panels. This kind of soiling prevents your panels from producing the energy they could if they were constantly clean. 

Depending on where you are located, regular solar panel cleaning can increase your annual solar production 10-20%, though increases above 30% are not uncommon. If you want to ensure that your solar panels are operating at peak efficiency, you need to clean them regularly.

What is the best way to clean your solar panels?

The first thing to consider when choosing a way to clean solar panels is whether or not the process in question might void solar panel warranties. Many traditional solar panel cleaning systems utilize practices that can void warranties such as using hard water, chemicals, or brushes with stiff bristles. Warranties can also be voided by putting cold water on hot glass – the thermal stress will eventually crack the solar panel glass. Furthermore, many solar panel cleaning systems require manpower, which introduces the added risk of human error into the equation; panels can easily be damaged if someone steps on them or even leans too hard on them.  

The best way to clean solar panels is to keep them clean all the time and to avoid the common mistakes listed above. RST NightWash™ uses a warranty-complaint process to safely and effectively clean your panels. Our unique filtration process ensures that the water used is soft, pure, and chemical-free. Our patented system uses low water pressure to protect your panels and our automated system cleans at night during hours that comply with the guidelines of solar panel manufacturers.

The RST NightWash™ system already cleans over 2 million panels every night for optimized performance, and we have never experienced a panel warranty issue.      

How much does it cost to clean your solar panels?

How much it costs to clean your solar panels depends on if you are using a service or a product.

Solar panel cleaning service prices vary depending on factors such as the distance from the site to the cleaning company’s headquarters, ease of access to panels, ease of access to water, etc. For residential systems, there is typically a fee for the cleaning business to come to the house ($100 - $200) plus a cost per panel ($1 - $3). For commercial systems, costs vary depending on the type of installation: $0.35 - $0.60 per panel for ground mount systems, $1.00 - $1.75 per panel for rooftops, and about $3.00 per panel for carports. 

There are two important things to keep in mind when it comes to solar panel cleaning services: (1) cleanings need to be scheduled regularly in order to maintain peak production, which drive up your cleaning costs; and (2) if it is windy the day after the cleaners come, your panels are already dirty again.

But solar panel cleaning doesn’t have to be a service; it can be a product. You don’t need to schedule a car wash every time your windshield is dirty. That’s why you have a  windshield wiper! Similarly, with an automatic panel cleaning product like RST NightWash™, you can install a system once and enjoy the benefits of constantly clean solar panels for 25 years. The levelized cost per cleaning reduces down to less than $0.01 per panel over 25 years.

Can you get self-cleaning solar panels?

Yes! RST NightWash™ is the leading self-cleaning system in the world and cleans more than 2,000,000 panels each night. Our fully automated system has almost no moving parts and is controlled by an app on your smart phone. You simply select the frequency you want and carry on with more pressing tasks in your busy life. RST NightWash™ is as easy as that – just set it and forget it. 

How do self-cleaning panels work?

The RST NightWash™ system connects to a water source, such as a spigot on the side of a house*. The water then goes to the control box where it is filtered through our state of the art filter technology. The water is then distributed through nozzles across the whole panel preventing your panels from getting dirty in the first place, and without limescale build up. The cleaning process occurs at night with chemical-free water at low pressure. These features preserve the panel warranty in the long run.

*For commercial customers, water can be accessed in a number of ways such as by tapping into irrigation piping in a nearby field or using municipal water from a building. And in cases where water is not readily available, a water tank can be used. 

Can you use a pressure washer to clean your solar panels?

Pressure washers can damage your solar panels and void the warranty. RST NightWash™ does not require high pressure washing because panel cleanings occur at least once a week. This regularity means that not even bird excrement can stay on the panels for long.

Don’t you need to scrub your panels to clean them?

No. Because RST NightWash™ cleans panels regularly, even the toughest types of soiling don’t have a chance to build up and cake on to the point where scrubbing would be necessary. 

How much water does RST NightWash™ use?

RST NightWash™ uses between 1 and 1.5 quarts of water per panel per cleaning. Rates in California for 1 HFC (748 gallons) range up to $10/HCF. Therefore, the cost of cleaning 100 panels using 1.5 quarts per panel would be $0.50 at the highest water cost. This translates to $36 in water cost to wash 100 panels once a week for an entire year.

How much electricity does RST NightWash™ use?

Because RST NightWash™ runs off water pressure, very little electricity is needed. Our residential systems use two AA batteries. Our commercial systems use about 100 kilowatt-hours per year, which is generally less than $20 per year in most utility service territories. 

Does RST NightWash™ cause dirt to build up at the bottom of the panel?

This is unlikely. Dirt will only build up at the bottom of the panel if it is below a 1-degree tilt. Above a 3-degree tilt, the RST NightWash™ system provides sufficient water flow so dirt and water drains over the lip edge of the panel. For panels tilted between 1 and 3 degrees, RST uses a special drainage clip to ensure that dirt and water flows off the panel.    

Does RST NightWash™ clean the entire solar panel?

Yes. Our proprietary nozzle evenly distributes water across the entire panel. 

Will RST NightWash™ void my panel warranty?

No. The RST NightWash™ system has cleaned over 2 million panels every night without a single panel warranty issue. The system uses patented clips to mount the nozzles to the solar panel edge similar to how a phone case attaches to an iPhone. These clips do not react to the aluminum solar panel frame. The nozzles spray soft, filtered water onto the panels at night when there is virtually no risk of thermal stress. Panel manufacturers have reviewed the RST NightWash™ technology and perceive no panel warranty issues with the technology.


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