Free Calculator for Dirty Solar Panels and Cleaning Profit

Want to quickly find out whether dirt on your panels is costing you yield? The dirty solar panel yield loss calculator gives you an initial, practical estimate based on your inverter data, so you can immediately see whether professional cleaning or inspection is worthwhile.

Dirty solar panels and loss of efficiency: what is really going on?

Loss of efficiency due to dirty solar panels means that dust, pollen, bird droppings and moss block sunlight, with a direct impact in kWh and pounds for households and SMEs in the UK. How much loss do dirty solar panels cause? In practice, we usually see between 3 and 15 per cent loss of yield, and in extreme or long-term neglected cases it can be even more, but the difference depends greatly on the situation. Guessing is not helpful; measuring with your inverter data or a visual inspection provides much more reliable figures. For those living in Belgium, every percentage point of yield loss counts: lower own consumption costs, less feed-in and therefore direct financial consequences.

• Type of pollution, short and sweet: Fine dust and pollen often cause a 3–6 per cent loss, while a thick layer of moss or a lot of bird droppings can easily double that locally.
• Roof orientation and pitch: Steeper, south-facing roofs clean themselves more effectively, while flat or east-west systems remain dirty for longer and suffer greater yield losses from solar panels.
• Regional factors and environment: Proximity to agriculture, busy roads or industry increases pollution and thus the loss of yield from dirty solar panels.
• Age and maintenance history: Older installations without regular maintenance show a faster structural loss of efficiency in solar panels than recently maintained systems.

In short, poor maintenance costs you yield; that is why we at Solarco say: we measure, we don't guess. Professional cleaning, periodic maintenance inspections and reporting are the safe, yield-oriented way to monitor the yield of your solar panels in Belgium. See also our Solar panel inspection for how we approach this.

Dirty solar panel efficiency loss calculator: quick estimate in 3 steps

With the dirty solar panel yield loss calculator, you can get a realistic estimate of your loss in just a few minutes, based on figures rather than gut feeling. You start with your inverter, note down a few key values and compare them with a clean reference. This allows you to see immediately whether your solar panels are still doing what they should or whether there is a structural loss of yield due to dirty solar panels. This simple solar panel yield calculator is not a substitute for a technical measurement, but it is a smart filter to help you decide whether further investigation or cleaning is worthwhile.

A simple example: suppose your reference yield is 4,000 kWh per year and your current inverter shows 3,600 kWh, then you are 400 kWh or 10 per cent short, which is the order of magnitude that we want to reveal with the dirty solar panel yield loss calculator. In Belgium, with energy prices between roughly 0.25 and 0.40 euro per kWh, this quickly adds up to a loss of 100 to 160 euro per year. On our page about dirty solar panels and loss of efficiency we explain in detail which factors play a role in this. If you would like to delve deeper into the return on investment of solar panels in Belgium, you will find Yield Solar Panels additional context and reference figures.

Step 1: collect your yield data

For step 1, open the app or display of your inverter and note down the total annual yield and, if possible, the monthly yield from a recent sunny period. Preferably choose the same month as last year, or a month with weather conditions similar to the test period used as a clean reference in many calculators. Also note down how many kWp your installation has, so that you can easily calculate the kWh per kWp later and compare this with the dirty solar panel yield loss calculator. If you prefer a structured approach, you can use a simple Excel spreadsheet or the tips on our page. Expert tips, create a brief overview of production per month.

Step 2: calculate your loss of yield due to dirty solar panels

For step 2, compare the measured yield with your clean reference and express the difference as a percentage. For example, take your yield for May this year and divide it by the yield for May last year, or by a realistic reference value that you can find at Yield Solar Panels; anything below approximately 90 to 95 per cent deserves extra attention. The loss percentage you calculate in this way is your first dirty solar panel yield loss calculator result and gives an indication of whether dirt, moss or technical problems are at play. If you see a deviation of 5 to 15 per cent, it is worth having further measurements taken to see whether professional cleaning with before and after results Cleaning your solar panels can significantly increase their efficiency.

Factors determining the loss of efficiency of dirty solar panels

Not every installation loses the same amount due to dirt, which is why every dirty solar panel efficiency loss calculator is always an estimate based on probable circumstances. A house in a quiet residential area around Herentals mainly has to deal with fine dust and some pollen, while an SME along a busy road or near a stable is much more likely to suffer from stubborn deposits and moss. The slope, orientation and age of your panels also determine whether the loss is closer to 3 per cent or closer to 15 per cent. With a professional inspection and maintenance, an experienced technician will consider all these factors together, rather than guessing with an average.

In our practice in and around Herentals, we see installations that, despite the same dirty environment, score differently, solely due to the degree of inclination, cable route and previous maintenance history. A flat commercial roof with years of deferred maintenance can lag behind structurally by 10 per cent or more, while a sloping roof with regular maintenance often remains within the margin of error of 3 to 5 per cent. So use the results of a dirty solar panel efficiency loss calculator primarily as a signal to take targeted action, not as absolute truth. With photos, measurements and a short report, you can turn a rough estimate into a concrete plan.

Type of contamination: dust, moss and bird droppings

• Light dust and pollen evenly distributed across the panels usually cause a 2 to 5 per cent loss in solar panel efficiency, especially if the rain does not wash it away completely.
• Grease deposits caused by traffic or industry can reduce yield by 5 to 10 per cent, especially on low slopes where dirt tends to accumulate.
• Moss along the edges and in frames hinders drainage and can cause localised losses of 10 to 20 per cent, with a risk of hotspots and damage.
• A significant amount of bird droppings on solar panels not only causes dirty solar panels and loss of yield, but in extreme cases can even make individual cells appear to be faulty.

Rain has little effect on this type of contamination, and cleaning dirty solar panels is more than just a cosmetic procedure. During maintenance, we not only look at the visible layer of dirt, but also at moss formation on the edges and any discolouration or hotspots. With targeted cleaning in accordance with the guidelines at how to clean solar panels and soft material prevents scratches and new deposits. This allows a technician to get the most out of every cleaning session, and afterwards you can see on the inverter how much loss was actually caused by dirt.

Location of your roof and seasonal influences

The location of your roof also plays a major role in the ultimate loss of efficiency of solar panels. Flat roofs on SMEs or apartment buildings in Antwerp and the Kempen region retain more water, causing dirt and pollen to stick to them and resulting in a loss of 10 to 15 per cent if they are not cleaned in time. East-west installations and roofs near agricultural or industrial areas are more likely to suffer from seasonal peaks in pollution; a targeted solar panel maintenance or a plan according to how often to clean solar panels helps to stay ahead of those peaks. During an inspection, an experienced Solarco technician will quickly identify where your yield is leaking and provide you with a short report containing clear photographs and concrete recommendations in understandable language.

When should you clean your solar panels and how much does it yield?

The most important question is not whether you should ever clean your panels, but when and how much that will yield in kWh and euros. Dirty panels that produce 5 to 10 per cent less energy can quickly mean a loss of 150 to 300 kWh per year for an average family in Belgium, depending on the size of the installation. With energy prices around 0.25 to 0.40 euro per kWh, that's 40 to 120 euro per year literally left on your roof. A dirty solar panel yield loss calculator gives you a rough idea, but you'll only see the real savings after a proper professional clean.

Maintenance frequency for private individuals

For private individuals, a dirty solar panel yield loss calculator is useful as an indicator, but you should determine the actual maintenance schedule based on your observations and your inverter data. If, after the winter, you notice a clear dull haze, green deposits or streaks of bird droppings, and your annual yield is lower than in previous years, then it is time to take action. With the guidelines on how often to clean solar panels and cleaning solar panels you can make a basic plan, but on difficult or high roofs it is have solar panels cleaned often the safest choice. This allows you to keep the installation in good condition without the risk of falls or damage caused by incorrect products.

Maintenance plan for SMEs and businesses

For SMEs and companies, it is even more worthwhile to incorporate cleaning and inspection into a fixed maintenance plan, rather than responding ad hoc to complaints about lower yields. Especially on flat company roofs, agricultural barns or sites along busy roads, contamination can cause a noticeable loss of efficiency in solar panels within a few months. A periodic plan in which we clean every 1 to 2 years and at the same time carry out a brief solar panel maintenance and visual inspection prevents surprises on your energy bill. With clear planning and transparent prices via, for example, solar panel cleaning price and a tailor-made quote for solar panel cleaning companies, As a business manager, you know exactly what it costs and what the potential returns are.

Questions and answers about dirty solar panels, efficiency and cleaning

Are you unsure whether the loss on your inverter is really due to dirt, or are you wondering whether solar panels will still be worthwhile in 2025? In this question and answer section, we have compiled the doubts we hear most often from families and SMEs. We take a sober approach to figures on solar panel yield loss, without scaremongering but also without minimising the problem. You can also read our position on whether or not to clean solar panels, and what options are available for solar energy without solar panels on your roof.

How much loss do dirty solar panels cause?

Based on practical figures and studies, we usually see a loss of 3 to 10 percent with normal soiling, with peaks of up to 15 percent in installations that have been neglected for a long time. This ties in nicely with what you see in a dirty solar panel yield loss calculator: if your yield is structurally more than 5 percent lower than a clean reference, then it is time to take action. On our page about dirty solar panels and loss of efficiency and in the blog cleaning solar panels: nonsense or not we explain the causes that often play a role. This allows you to distinguish between natural variation and genuine, structural loss of yield due to dirty solar panels.

Is it worthwhile to clean solar panels?

Cleaning solar panels is not a magic trick, but it is a logical step if the figures show it to be necessary and the installation is visibly dirty. Anyone who has safe access and uses the right materials can do basic cleaning themselves, but on steep or commercial roofs, it is wiser to work with a specialist such as Solarco. Using a combination of a dirty solar panel efficiency loss calculator, inverter data and a professional inspection, you can determine whether cleaning will yield the most benefit or whether other measures are more important. And if you don't have a roof, you can still benefit from solar energy without solar panels on your home or commercial building through a green energy contract or a solar park.

Do not let your returns slip away: schedule an inspection with Solarco

A professional inspection and cleaning stops measurable loss, and with our dirty solar panel yield loss calculator, you get a quick, practical estimate as a starting point. Solarco works locally around Herentals and Antwerp, safely at height and with clear before and after reports so you can immediately see what delivers profit. We offer a concrete inspection that measures results, not guesses, followed by a proposal for cleaning or periodic maintenance. This combines safety, efficiency and transparency in a single plan.

• Visual inspection of panels, mounting materials and connections
• Thermographic scan and performance measurement per string
• Before-and-after yield comparison with clear figures
• Safe cleaning and repair advice where necessary
• Customised maintenance plan with quotation

After the inspection, you will receive a clear report with measurements and recommendations, plus a no-obligation quote for any cleaning or follow-up work. Dirty solar panels cause measurable losses, and the dirty solar panel efficiency loss calculator gives you an initial indication; a Solarco inspection then provides certainty and a plan to maximise your yield., request a quotation.