The Short and Long Term Benefits of Solar Panel Cleaning

This guide covers everything you need to know about solar panel cleaning and when it’s time to bring in a professional service provider.

What Is Solar Panel Cleaning: a Quick Definition?

When sunlight hits solar photovoltaic (PV) panels, they convert the sun’s energy into clean solar electricity for homes, businesses, and communities. More sunshine means more electricity, which is why solar power is often associated with sunny climates like California’s and Spain’s.


However, this is only part of the equation.


The goal is to optimize the amount of sunshine reaching the solar panels. Professional installers factor this in when positioning and orienting PV modules. But maximizing sun capture also requires keeping the panels free of dust, leaves, snow, and other debris.


Your solar panels may require regular cleaning so they produce as much clean energy as possible. Doing so decreases your reliance on expensive grid electricity, allowing you to save more money and generate fewer greenhouse gases.

Is Solar Panel Cleaning Really Necessary?

According to a research study conducted by the University of Malaga, prolonged periods without rain led to dust buildup, which reduced daily solar output among PV systems by 20%.[i] These findings create a fairly strong case for regular solar panel cleaning.


However, other studies have reached very different conclusions.


A 2013 research paper from the University of California San Diego (UCSD) found that over a 145-day summer drought in California, solar panel performance fell by only 7.4%.[ii] Researchers further concluded that at current utility rates, cleaning a typical 5 kW residential solar installation would only save homeowners $20 off their electricity bill – which is substantially less than what professional solar panel cleaning normally costs. The panels in the study only lost about 0.05% efficiency on a daily basis.


In the words of Jan Kleissl, lead researcher of the UCSD study, “Most homeowners won’t get their money back for hiring someone to wash their rooftop panels.”


It’s hard to argue with such an exhaustive study. But it’s also difficult to ignore one’s own experience – like how leaving a dirty car out in the rain doesn’t automatically make it clean. In fact, carwashes are often busiest right after a heavy storm.


Our own analysis is that when done properly and at the right frequency, solar panel cleaning can help:

  • Maximize a PV system’s power output
  • Increase utility bill savings for owners
  • Deliver measurable carbon savings

Moreover, this cleaning is especially important if your PV system uses string inverters instead of microinverters. Both are responsible for converting direct current (DC) solar electricity into alternating current (AC) power for your home or business.

  • With string inverters, performance dips in one panel can have a huge impact on the other panels in the system – similar to old-fashioned Christmas tree lights strung up in series.
  • Microinverters make the DC > AC conversion at the panel level so that performance drops in one solar module are localized to that specific panel.
  • Although there are compelling reasons to clean solar panels, how often should washing occur?

    When Should You Clean Solar Panels?

    The most obvious indication that your panels need cleaning is when you see a decrease in PV system performance. It’s natural for there to be daily, weekly, or seasonal fluctuations in solar power generation. But prolonged and unexpected decreases in output is a sign that something is wrong. PV panel cleaning is the easiest and cheapest of all troubleshooting steps – which is why many customers start here first. If more drastic intervention is required, you may need to invest in solar panel maintenance to restore modules to former production levels.


    Some homeowners and businesses schedule periodic cleanings throughout the year – based on local conditions:

  • Cleaning panels after snow season makes a lot of sense in northern climates
  • Solar panel cleaning is also common during the end of autumn, when the leaves stop falling
  • The sam is true in late spring when pollen counts start to go down again

  • Those who live in arid solar hot spots like California or Arizona might schedule panel cleaning during the driest times of the year when dust buildup threatens system performance.


    Which frequency to choose for your own solar panels is ultimately a personal choice. But if you’re not generating the utility bill savings you were hoping for, cleaning your modules could help boost performance. This is especially true if you live in a region with excessive dust, pollen, pollution, foliage, or snow.

    Bird droppings aren’t something that easily washes off with rain – meaning solar panel cleaning may be unavoidable. The same goes for PV modules installed horizontally. Flatter solar panels tend to collect more dust, and thus, require more frequent washing.


    In addition, these cleaning requirements can grow considerably as the number of panels increases. Mega solar farms must constantly clean their modules as even minute performance dips can lead to huge losses when multiplied across thousands of panels.


    As a residential or commercial solar customer, you won’t have to stick to this same schedule. But it’s important you understand the potential benefits of giving your panels an occasional wash.

    How to Clean Solar Panels

    The most popular cleaning method involves using soap and a regular garden hose, which is particularly common among homeowners looking for cost-effective DIY options. However, this approach can often reduce total PV system performance due to streaking and leftover residues.


    If you’ve ever tried cleaning a window with soapy water, you likely already understand. Not only are the windows not truly clean when you’re finished, but the residue actually makes it easier for dust and pollen to cling to the surface. And unfortunately, rinsing with water isn’t enough since soap film can linger for a long time. This is basically the principle behind scented soaps. Their molecules need time to dissipate, which is why you always smell “fresh” after taking a shower or washing your hands.


    Fortunately, there exist several over-the-counter cleaning products specifically designed for solar modules. Some of the more popular ones include Glass Gleam, One Shot, and PolyWater– all of which are available at hardware stores and on Amazon. Most of these products use non-soap-based solvents that modify the surface tension of water to prevent beading. Instead, the water develops a smooth and continuous layer that helps dislodge dirt, dust, and pollen. These industrial products also have the added benefit of using less overall water in general – minimizing the environmental impact of regular panel washing.


    Many professional solar panel cleaners also have other tools in their arsenal – including deionized water. With this specially treated water, minerals have been stripped out using reverse osmosis, which is why it often goes by its other name, “demineralized” water. What’s left behind is a very pure form of H2O that acts as a magnet for particles.


    When demineralized water is coupled with a rotating brush, it’s possible to agitate and dislodge grime so that it washes away completely. Once the water evaporates, the panels remain free of streaks or residue. Deionized water is also chemical-free – a claim that even the most eco-friendly cleaning solutions can’t match.

    Common Mistakes When Solar Panel Cleaning

    Using soap is the #1 taboo in the industry. But below are some other common solar panel cleaning mistakes to avoid.

    1. Not Having the Right Equipment

    Most PV systems are rooftop installations, which makes solar panel access a real challenge. In addition to industrial-grade solvents, many professionals often bring ladders, harnesses, water tanks, and specialized poles and brush to make the job easier.


    The average homeowner doesn’t have all these supplies and safety gear – but that doesn’t stop them from trying. If you also decide to go the DIY route, just be sure to avoid using anything hard or abrasive that might damage your solar panels. For example, it’s common to use garden rakes to clear away snow buildup. However, be careful since the metal tongs can scratch your panels and void their warranties.

    2. Ignoring Personal Safety

    In addition to lower quality results, DIY solar panel cleaning increases the risk of accident and injury if you don’t know what you’re doing. Remember that it’s not just falling you have to worry about. Mixing water and high voltage electrical equipment is a dangerous combination.

    3. Cleaning on the Hottest Days

    Because of their dark surfaces, modern solar panels get hot very quickly when exposed to direct sunlight. And these higher temperatures mean that module surfaces dry faster than normal, which leads to streaking – even when using “streak-free” cleaning solutions. Moreover, the sudden shock of cold water hitting hot-tempered glass can crack your PV panels, potentially voiding their warranties. And you may need to pay out-of-pocket for solar panel repairs[WU4]. This is why you’re better off cleaning at dawn, dusk, or on overcast days to allow for slower and more even drying.

    Of course, the easiest way to avoid these mistakes is to outsource the job to solar panel cleaning companies that know what they’re doing.


    And here’s why.


    According to Q1 2020 data from the Solar Energy Industries Association (SEIA), the average cost for residential solar installations is about $2.83/W – meaning a standard 5 KW system costs around $14,000.[iii]


    Your own system might be above or below this average. Either way, you’ve still invested thousands of dollars. And it makes sense to protect that investment – just as you would with scheduled car maintenance or dental cleanings. Regular upkeep is usually cheaper than emergency intervention.
    The question is – how do you find the right professionals for the job?

    How to Pick a Solar Panel Cleaning Company

    Many PV installers include solar cleaning as an add-on service. And if your original installer does too, working with them again is probably the easiest approach. Of course, this assumes the experience was positive the first time around – and you trust them to do a good job again.


    However, most solar installers don’t offer this service. And you may need to find a dedicated outfit that specializes in solar panel cleaning. If you choose this route, here are some important criteria to consider.

    1. The Method

    Always ask how they clean solar panels. You want someone whose method is:

  • Effective at boosting solar PV panel performance
  • Safe for the panels themselves (i.e, no scratching)
  • Environmentally friendly (i.e. no harmful toxins)
  • If they use soap or caustic chemicals to do the job, you’re probably better off choosing another solar panel cleaning service.

    2. Experience

    The barrier to entry for PV installers is very low, with many amateurs labeling themselves as “professional technicians.” For the much simpler job of solar panel cleaning, the bar is even lower.

    As such, it’s important you only partner with professionals with extensive (and verifiable) experience. More specifically, you want someone familiar with PV systems like yours since:

  • Solar carports, ground-mounted systems, and rooftop installations all call for different types of cleaning equipment
  • Residential solar cleaning teams tend to be much smaller than those used for commercial projects
  • Regardless of your own PV installation, the goal is to find a solar panel cleaning service that can complete the job well – with a few hidden surprises as possible.

    3. Geography

    The basic mechanics behind solar panel cleaning are fairly straightforward. But you still want someone local who understands the weather and climate conditions specific to your geographic region. That way, they can use the most effective method for whatever “accumulation” issues you’re facing:

  • Some regions (like the Rust Belt) are notorious for their high pollen counts
  • In the arid Southwest, dust and sand may be more pressing issues
  • In New England, you want a team that knows how to navigate snow
  • 4. Availability

    Unlike solar panel repairs, PV module cleaning usually isn’t a super urgent issue. But it’s still nice to have someone who is responsive and available. Just keep in mind that following pollen season, dry spells, and snowstorms, most solar customers in your region are likely facing the same issues you are. So be patient if there’s a backlog.

    5. Reviews

    As with any contracting job, it never hurts to check out honest reviews from previous customers. Most solar panel cleaning companies will happily provide you with “glowing” testimonials they’ve hand-picked. But be sure to research independent third-party sites like Angie’s List or Yelp for more objective feedback.

    6. Cost

    Every budget is different. You’ll need to conduct your own cost/benefit analysis to determine if hiring a solar panel cleaning service is worth the price. This, of course, depends on what the price actually is – and how bad your own PV system’s performance has become.


    Keep reading for a breakdown of what you can expect to pay for a professional cleaning service.

    What Are the Costs for Solar Panel Cleaning?

    Solar panel cleaning costs vary due to huge differences between PV installation sizes, system locations, module orientations, and the type of debris being cleared. According to the residential contracting portal, Fixr.com, the average price hovers between $150 and $330 for a small 2 kW residential solar installation.[iv]


    When it comes to solar panel cleaning service cost:

  • Some professionals charge flat rates – regardless of the PV system size or number of panels
  • Others charge on a per-panel basis, with an average of around $15 – $35 per module.
  • [v]

    If you clean your panels yourself, the only direct cost is water. But there are many potential hidden costs in the form of:

  • Personal injury risks
  • Reduced performance
  • Potential breakages
  • Voided warranties
  • Is Solar Panel Cleaning Covered by My Warranty or O&M Contract?

    Panel cleaning is almost never covered by manufacturer warranties. It is up to each individual to keep their own modules clean and in prime condition. Some installers include solar panel cleaning in their performance guarantees – or as add-on services. And you’ll need to read the fine print in your own agreement to determine if your PV system qualifies.


    The same is true for operations and maintenance (O&M) contracts. You would assume that regular cleaning comes standard with most of these agreements. But it’s best to read the fine print for exact details since every O&M contract is different.

    Conclusion

    Depending on where you live, DIY solar panel cleaning and occasional rain might be enough to keep your PV system in optimal working condition. But if you’re dealing with heavy accumulation or notice substantial performance drops, a professional provider might be the best option.

    It takes time to vet potential candidates – especially if this is your first time having your own system professionally cleaned. 365 Pronto’s Solar Operations and Maintenance Platform can help you quickly connect with experienced, knowledgeable, and affordable solar panel cleaning professionals in your area.


    To learn more, contact the 365 Pronto Team for a free platform demo.


    References:

    [i]https://www.irishellas.com/files/Analysis-of-dust-losses-in-photovoltaic-modules_2011.pdf
    [ii]https://ucsdnews.ucsd.edu/pressrelease/cleaning_solar_panels_often_not_worth_the_cost_engineers_at_uc_san_diego_fi
    [iii]https://www.seia.org/research-resources/solar-market-insight-report-2020-q2“[iv]https://www.fixr.com/costs/solar-panel-maintenance#solar-panel-cleaning-cost“[v]https://www.fixr.com/costs/solar-panel-maintenance#solar-panel-cleaning-cost