Tips for solar panel cleaning and maintenance

Solar panel maintenance isn’t such a big deal. Read this guide for a list of things you actually need to do.

— by The Solar Nerd — About a 10 minute read.

Are you a homeowner with solar panels? Congratulations! Hopefully it’s working out for you. One of the great things about solar panels is that they just sit there, silently turning photons into electricity and making you money. They can essentially be maintenance-free for 25 years. That said, people tend to have a lot of questions about ownership and maintenance, so here’s some answers to common questions people have.

How often do you need to clean your solar panels?

If you have a ground mounted solar array and the panels are easily accessible, go ahead and clean them once in awhile if you like. Skip to the section below for tips on how to safely clean your solar panels without damaging them.

But if you have a rooftop array that is difficult to reach, the short answer is: rarely, if ever.

Longer answer: dust, dirt, and pollen that collects on the surface of your panels will reduce the amount of light that the cells receive, decreasing the electricity they generate. Wind and rain are natural processes that help remove this soiling, although they alone won’t keep them squeaky clean. But does that matter?

A worst case scenario is that you live in a desert where it hardly rains and sandstorms are a regular occurrence - say, Saudi Arabia. Under these conditions, your solar panels might get dirty enough that power losses climb into the double digits - around 30%, according to one study from the Middle East.

For the United States, a more realistic worst case would be a prolonged drought, which has become more frequent in the western states. One study in California showed that after an exceptionally long 145 day drought, power losses were around 7.4%. But even in that extreme situation, at an average electricity price of $0.18/kWh in California, the value of the lost electricity is nowhere near close enough to make it worth it to pay a company to come clean your panels.

Let’s do some quick math: on a good day, an average system might generate 40 kWh. Since it’s a drought, let’s say it’s perfectly sunny every day, and in a month your system generates 1,200 kWh. A loss of 7.4% would be 89 kWh, which is worth $16. (Your numbers will vary depending on the size of your system, so do your own math for a better estimate.)

Paying a company to come to your home to clean your panels will cost much more than that, even if you do it only every couple of months. So, if you can reach your panels easily and clean them yourself without damaging them, go ahead and do it. But it’s hard to imagine any scenario where it’s worth paying someone to do this maintenance for you.

You should clean bird poop and leaves off your panels

The one case where you should clean your panels is if there is any type of dirt or debris that isn’t getting cleaned away by wind or rain. This can include stubborn bird poop that has hardened on the panel and isn’t getting washed away, or leaves that have fallen on the panels and maybe gotten stuck against the edge of the frame or between panels.

You want to clean this type of debris off because it can cause hot spots in the panel, which is an electrical phenomenon that happens when only part of the panel is shaded. Localized shading on a panel can actually cause the shaded cells to heat up because the shaded cells must carry the electrical current of neighboring cells that are still operating.

That extra heating can stress the shaded cell and its wiring, and accelerate a failure. This type of failure is called a hot spot. In extremely rare cases, an electrical failure like that can cause a fire.

Solar panels all have built-in devices called bypass diodes that protect against hot spots. There are multiple bypass diodes for redundancy, so a catastrophic failure is very rare. Still, non-catastrophic failures (one that doesn’t end in a fire) due to hot spots do happen, so keeping the crap (literally) off your panels is a good idea.

How do I clean my solar panels?

If your photovoltaic system is easily accessible and you can reach them without a risk of smashing the glass with an extension pole, you can do it yourself.

The top layer of a solar panel is tempered glass designed to withstand hail strikes. It’s very strong, but you can still damage or scratch the glass if you’re not careful. In addition, the glass may have anti-reflective or water repellant coatings, so it’s best to avoid the use of any cleaners that contain harsh chemicals, including Windex.

Solar panel cleaning equipment

To clean your solar panels, use the same equipment you would use to wash your windows - a sponge or microfiber cloth. It’s actually not necessary to squeegee the glass, and it’s better if you didn’t, because squeegee tools usually have a metal part that holds the rubber squeegee in place. It would be too easy, with the squeegee attached to the end of a long, flexible pole bouncing up and down, to accidentally hit the glass with the sharp metal edge of your tool.

So, skip the squeegee. You don’t need your solar panels to be streak-free. You just need to clean any dust or dirt off. Just use a soft tool. I’ve personally used one of these (the cloth end):

2-in-1 Microfiber Scrubber and Squeegee, 14”

2-in-1 Microfiber Scrubber and Squeegee, 14

It’s cheap and works well, and then you can also use it to clean your windows. (It’s about $17. Find the latest pricing on Amazon.)

Another great option is a flow-through brush with a flow-through pole. “Flow-through” means that you can attach a garden hose to it, and the water will flow out of the brush head. Very handy, because it means you don’t need to dip your brush into a bucket. Make sure that the pole is flow-through as well. These are a good combo:

Mr. LongArm Soft Flow-Thru

Mr. LongArm Soft Flow-Thru

The thing that’s good about this is the rubber bumper around the perimeter of the brush, so it won’t scratch your panels. It’s flow through, so the water will run out the face of the head. It’s about $15. (Check current pricing on Amazon.)

Mr. LongArm Hydrasoar Flow-Thru Extension Pole, 6-to-12 Foot

Mr. LongArm Hydrasoar Flow-Thru Extension Pole, 6-to-12 Foot

This extension pole is flow-through, meaning that you attach a garden hose at the bottom, and a internal channel carries the water through the top end where you can attach a flow-through accessory, like the brush above. Extends up to 12 feet, which should be enough to reach your roof when you’re standing on a step ladder. It costs around $42. (Check current pricing on Amazon.)

Soap or not?

The glass used for solar panels have special coatings that minimize reflectivity and repel water. Harsh cleaners can damage this coating. Dish soap is probably gentle enough to not harm the coatings, but there’s really no reason to use it. Just use plain water. If your municipal water is very hard, use distilled water to avoid leaving mineral deposits on the glass.

Be careful if you’re using a hose

You could also simply hose off the panels, but you want to be very careful when doing this. Don’t use a high pressure spray, or even a garden hose with a concentrated stream.

One of the ways that a solar panel can fail is by moisture penetrating the seal between the frame and the glass. If you blast your solar panels with a hose, you could easily force water through the seal. A buildup of humidity inside the panel can cause corrosion of the wiring and an eventual failure of the panel.

So if you’re using a hose, use a light spray setting. Also, be very careful to spray only the top surface of the glass, and not the backside of the panels where there are electronics and wiring.

Better yet, use a flow-through cleaning device like the ones listed above.

Check your power generation before and after

It’s a good idea to check your power generation before and after cleaning to see what the improvement in power output from cleaning was. This will let you know if this extra maintenance was worth your time.

What about snow on my panels?

The Solar Nerd lives in Buffalo, New York. It snows a lot here. When it snows lightly, the snow will blow off or quickly melt off when it warms up. But in a more significant snowfall, the snow will accumulate and completely block any light from reaching the panels. It takes about an inch or two of accumulation on the panels for this to happen. When the temperature warms up again, it all slides off in a big mass.

My guess is that I lose about two to three weeks’ worth of power generation a year because of this. My rooftop panels are not easily accessible from the ground, so I don’t bother cleaning them. It’s just not worth going out in the cold and risking my neck on a ladder in December to gain a few extra kilowatt hours. The sun is lower in the sky in the winter, and it’s often cloudy, so I don’t lose much power anyway.

There are days where its bright and sunny and my panels are completely underneath a blanket of snow. These are times when I could easily reach up and brush them off, but those days are infrequent. Again, it’s really not worth a hospital bill to risk going up on an icey ladder.

This is a case where a ground-mounted array has a clear advantage, but I wouldn’t choose ground-mount simply because it’s easier to maintain in the winter.

Critters like to live under solar panels

If you have a clear view from the ground, once a month you should look underneath your panels to make sure that any critters haven’t taken up residence. Birds and squirrels are known to make nests in the conveniently sheltered space between the panels and rooftop.

Squirrels pose a particular danger. They are actually the second largest cause of power failures in the US, after equipment failures. Squirrels enjoy chewing on wires, and if they nest underneath your panels, there is plenty of cabling and electronics for them to damage.

If you see critters taking up residence, you’ll need to call in a professional to have them removed before they do any damage.

If you have squirrels where you live, you should consider asking your solar installer to put in critter guards. This is especially true if you can’t see underneath your panels from the ground, and have no way of knowing if animals have turned your PV system into a hotel. Having these in place can save you maintainance costs down the road.

Critter guards are simply wire mesh that are clipped or nailed into place. There are a few vendors that make them. Here’s one example:

To learn more about squirrel guards and to find some recommended products, read my article on how to protect your solar array from critters.

Monitor your production

The main thing that a solar PV owner should do is periodically check the monitoring system that is supplied with your inverter. The system will let you know about any unusual drops in power output, and if you have power optimizers or microinverters, it can tell you when an individual panel is experiencing issues.

Some inverters will automatically notify you when an error is detected. For example, in the MyEnlighten software for Enphase, go to your name > Settings to see this option:

Screenshot from the Enphase monitoring software.

Select the last option to get an email when your Enphase system detects an issue. Other inverter manufacturers have similar features.

There really isn’t much to do

As you can see, there’s very little that is required to maintain your photovoltaic system. You’re mostly just keeping an eye on things and monitoring your production. Chances are that your system will silently generate electricity for a couple decades with no work on your part. That’s one of the reasons why solar is such a great technology.

Buying Solar For Your Home: The Complete Guide

This article is part of a series to help the homeowner go solar.