Hello! Are you wondering how your solar panels work and if you’re getting the most out of them? That’s normal. We hear a lot about efficiency, but what does that actually mean for a photovoltaic installation? We’re going to look together at how it’s calculated, what can change it, and how to make sense of the figures you’re given. The idea is to understand if your system is producing the electricity it could be producing, and how to ensure that’s the case. We’ll break it down, step by step, so you know exactly what you’re looking at.
Key Points to Remember
- The efficiency of a solar panel is the proportion of the sun’s energy it manages to convert into electricity. It’s measured as a percentage. The higher this figure, the better.
- To calculate efficiency, a simple formula is used: Peak power (Wp) divided by the panel’s surface area (in m²) multiplied by 1000. This 1000 represents the standard light intensity.
- Several things can affect this efficiency: the amount of sunshine, temperature, whether the panel is well-oriented and tilted, and even the cleanliness of the panel.
- It’s important to note the difference between the efficiency advertised in the laboratory (perfect conditions) and what you’ll actually get at home. Losses, such as those due to the inverter or heat, are normal.
- To get a good idea of your installation’s performance, you need to look at the system’s overall efficiency over a year, taking into account all elements and real-world conditions.
Understanding the efficiency of photovoltaic solar panels
The efficiency of a photovoltaic solar panel is a bit like a car’s fuel efficiency: it indicates how much useful energy can be extracted from it compared to what’s put in. In our case, we’re talking about the solar energy the panel captures and converts into electricity. It’s a figure expressed as a percentage, and the higher it is, the better. A panel with 20% efficiency means it converts 20% of the sun’s energy it receives into usable electricity.
Definition of solar efficiency
Solar efficiency, for a photovoltaic panel, represents its ability to convert incident solar radiation into electrical energy. It is calculated by dividing the electrical power actually produced by the solar power received by the panel’s surface. This ratio, expressed as a percentage, provides a direct measure of energy conversion effectiveness. For example, a 1.7 m² panel receiving 1000 W/m² of sunlight and producing 340 W of electricity would have an efficiency of (340 W / (1.7 m² * 1000 W/m²)) * 100 = 20%.
Efficiency as a performance indicator
Efficiency is a key indicator for evaluating the performance of a solar panel. It allows for comparison between different models and technologies. Higher efficiency means a panel can produce more electricity from the same surface area, which is particularly interesting when available space is limited. It’s important to note that efficiency is often measured under standardised conditions, called STC (Standard Test Conditions), which include 1000 W/m² irradiance, a cell temperature of 25°C, and a specific light spectrum. These conditions allow for a fair comparison between products, but actual efficiency can vary depending on installation and operating conditions. For example, a 400 Wp panel can generate between 350 and 500 kWh per year depending on its location and installation.
Conversion of solar energy into electricity
The conversion of solar energy into electricity is at the heart of how a photovoltaic panel works. This process takes place at the solar cell level, usually made from silicon. When photons from sunlight strike these cells, they release electrons, thereby creating a direct electric current. This current is then routed by cables to an inverter, which converts it into alternating current, usable by our electrical appliances. The cell technology, their purity, and how they are interconnected directly influence the efficiency of this conversion. Monocrystalline panels, for example, are renowned for their superior efficiency, often between 18% and 24%, while polycrystalline panels generally range between 14% and 18%.
It is essential to understand that the nominal efficiency of a panel, measured in the laboratory, is a reference. The actual electricity production will depend on many environmental factors and the installation itself, such as orientation, tilt, shading, and ambient temperature. A good understanding of these elements allows for optimising the overall production of your solar system.
Here is an overview of average efficiencies by technology:
| Panel Type | Average Efficiency |
|---|---|
| Monocrystalline | 18 % – 24 % |
| Polycrystalline | 14 % – 18 % |
Kilowatt-peak (kWp) is a unit used to assess the maximum power a solar system can produce under ideal conditions. It serves as a basis for comparing equipment and estimating the production potential of a solar installation. Elements such as geographical location, roof orientation, presence of shadows, and cell type influence the actual energy production, which may differ from the nominal kWp. Professionals use precise data and calculations to best size systems, taking into account your usual consumption and the characteristics of your building, to maximise long-term return on investment.
Calculating solar panel efficiency
To properly evaluate the performance of a solar installation, it is essential to know how to calculate a panel’s efficiency. It’s not that complicated once you have the right formulas and understand the technical terms. Efficiency, broadly speaking, is the panel’s ability to convert sunlight into usable electricity. The higher this figure, the better.
The standard formula for efficiency
The efficiency of a photovoltaic panel is calculated by comparing the amount of electricity it produces to the amount of solar energy it receives. The basic formula is: Efficiency = (Amount of electricity produced / Amount of solar energy received) x 100. To obtain a standardised measurement, standard test conditions (STC) are often used. These involve 1000 W/m² irradiance, a temperature of 25°C, and a south-facing orientation with a 30° tilt.
Practical application of efficiency calculation
For a more concrete application, efficiency can be calculated based on the maximum power a panel can generate, called peak power (Wp), and its surface area in square metres (m²). The formula then becomes: Efficiency = (Power Wp) / (Panel surface area m² x 1000). For example, a 400 Wp panel with a surface area of 1.7 m² would have an efficiency calculated as follows: 400 / (1.7 x 1000) = 23.5%. It is important to note that this efficiency is measured under ideal conditions.
Understanding peak power (Wp)
Peak power, often abbreviated as Wp, represents the maximum power a solar panel can produce under optimal laboratory conditions (the STC mentioned previously). It is a key data point for comparing different panels. For example, a 500Wp panel is designed to produce 500 watts under these ideal conditions. It should be noted that in real-world conditions, production will often be lower, but Wp remains the reference for evaluating the panel’s intrinsic capacity. A 3 kWp installation, for example, is composed of panels whose sum of peak powers reaches 3000 Wp. It should be noted that a 3 kWp installation can produce between 3,000 and 4,200 kWh per year, or between 8.2 and 11.5 kWh per day, depending on sunshine conditions and geographical location. For optimal production, it is often recommended to have approximately 6 solar panels, depending on the power of each panel [27a6].
The efficiency of a solar panel is an essential indicator for evaluating its ability to convert solar energy into electricity. It is measured under standardised conditions to allow for a fair comparison between the different models available on the market.
Solar panels have efficiencies that vary according to their technology. Monocrystalline panels, for example, generally show the best efficiencies, reaching 24% or more, while polycrystalline panels are typically between 14% and 18%. There are also newer technologies, such as flexible panels, which offer some portability but often have slightly lower efficiency, although technological advances are constantly improving their performance [c509].
Factors influencing panel efficiency
Several elements can affect the amount of electricity your solar panels produce. It’s not just about the panel’s nominal power, but also its environment and installation. Understanding these factors helps you better estimate your system’s actual production.
The impact of sunshine and temperature
Sunshine is obviously the main driver of solar production. However, the amount of sunlight received by your panels is not constant. It varies with the weather, season, and time of day. Beyond the simple amount of light, temperature plays an often underestimated role. Solar panels are designed to operate optimally at a specific temperature, usually around 25°C. When the panel temperature exceeds this threshold, their efficiency decreases. For each additional degree Celsius above 25°C, a loss of efficiency is observed, often between 0.3% and 0.5%. This means that on a very hot day, even with strong sunshine, production may be lower than on a cooler day with similar sunshine. New generation solar panels, particularly those using technologies such as heterojunction (HJT) or IBC (Interdigitated Back Contact) cells, show better heat tolerance, with lower efficiency losses per excess degree.
Influence of orientation and tilt
The orientation of your panels relative to the sun and their angle of tilt are crucial for capturing maximum solar energy throughout the year. Ideally, in the northern hemisphere, a due south orientation is best. However, other orientations such as south-east or south-west can also be very efficient. The optimal tilt depends on your latitude and the seasonality of your desired production. A tilt of approximately 30 to 35 degrees is often recommended for balanced annual production. A tilt that is too low or too high can reduce the amount of solar energy captured. For example, a due west-facing installation will produce less than an identical due south-facing installation, with a potential loss of up to 7% depending on conditions. It is therefore important to choose these parameters carefully when designing your solar installation.
Standard Test Conditions (STC)
It is important to know that the efficiencies announced by manufacturers are generally measured under very precise laboratory conditions, called Standard Test Conditions (STC). These conditions include 1000 W/m² irradiance, a cell temperature of 25°C, and a specific light spectrum. These conditions are rarely encountered in reality. Consequently, the actual efficiency of your solar panels in your daily environment will often differ from that indicated on the technical sheet. You must also consider losses related to the inverter, cabling, and potential partial shading, which can represent up to 10-15% of gross production. Panel cleanliness is also a factor: dust, leaves, or moss can reduce light capture and lead to an efficiency drop of 2 to 8% per year. Annual cleaning can therefore improve production.
The efficiency of a solar panel is a complex mix of its intrinsic technology and environmental and installation conditions. To obtain an accurate production estimate, all these factors must be taken into account, and one should not rely solely on STC figures.
Interpreting efficiency values
Understanding your solar installation’s efficiency goes beyond the figures displayed on a technical sheet. It involves analysing what these values concretely mean for your electricity production and your return on investment. Nominal efficiency, measured in the laboratory under ideal conditions, serves as a reference, but real efficiency, what you’ll get on your roof, is influenced by many factors. It is therefore essential to know how to decipher this data to make informed choices and anticipate the actual performance of your photovoltaic system.
The nominal efficiency of a solar panel is a measure of its ability to convert solar energy into electricity, as determined under standardised test conditions (STC). These conditions include an irradiance of 1000 W/m², a cell temperature of 25°C, and a specific light spectrum (AM 1.5). This is the value you will most often find on manufacturers’ technical sheets. However, it is important to understand that these conditions are rarely encountered in reality.
Real efficiency, on the other hand, is the efficiency your panel will produce under actual installation conditions. It is systematically lower than nominal efficiency due to several factors: increasing ambient temperature, panel soiling, actual orientation and tilt, as well as losses related to cabling and the inverter. A difference of a few percentage points between nominal and real is therefore entirely normal. For example, a loss of 0.4% per degree Celsius above 25°C is data to be taken into account.
Several elements can reduce the performance of your solar installation compared to its theoretical potential. It is useful to know these losses to get a more accurate estimate of your annual production. The most common losses include:
- Temperature losses: As mentioned, heat reduces panel efficiency. Technologies like IBC (Interdigitated Back Contact) cells are more resistant to this effect.
- Soiling losses: Dust, leaves, moss, or pollution can reduce the amount of light reaching the cells, leading to an efficiency drop of 2 to 8% per year.
- Shading losses: Even partial shading, caused by trees, chimneys, or neighbouring buildings, can have a significant impact on overall production.
- System-related losses: Inverters, cables, and connections also introduce losses, generally estimated between 10 and 15% of gross production.
It is crucial to consider these losses when evaluating the expected performance of your system. Good planning and regular maintenance can help minimise their impact.
Solar panel manufacturers often offer production guarantees, which are an indicator of their confidence in the durability of their products. These guarantees generally cover the power output of the panels over a given period, often 25 or 30 years. For example, a guarantee might stipulate that the panel will retain at least 85% of its nominal power after 25 years.
It is important to distinguish between the product warranty (which covers manufacturing defects) and the performance warranty. The latter ensures that the panel will continue to produce a certain amount of electricity over time. In Belgium, good efficiency for an installation in 2025 is generally between 18% and 22%, depending on the technology and installation conditions. Comparing these guarantees and understanding their scope will help you choose reliable panels and anticipate the natural degradation of performance over the long term. The objective is to ensure a good balance between the initial investment, the expected annual production, and the lifespan of the installation, by calculating the €/kWh produced ratio to optimise your return on investment.
Comparison of solar panel technologies
The choice of your solar panel technology has a direct impact on their performance and, consequently, on the amount of electricity your installation will be able to produce. There are several types of panels on the market, each with its own characteristics in terms of efficiency, cost, and aesthetics. Understanding these differences is essential for making an informed choice.
Monocrystalline panels are made from a single, high-purity silicon crystal. This manufacturing process gives them a uniform structure, which allows electrons to flow more freely. It is this structure that explains their superior efficiency compared to other technologies. Monocrystalline panels generally exhibit the highest efficiencies on the market, often ranging from 18% to over 22%. They are also recognised for their durability and good performance even in low light conditions. Although they are generally more expensive to purchase, their increased efficiency can translate into greater energy production over the long term, which can justify the initial investment. Their uniform black colour is also often appreciated for its aesthetic integration.
Polycrystalline panels, also known as multicrystalline, are made from fragments of silicon crystals melted together. This production method is less complex and therefore less expensive than that of monocrystalline panels. Consequently, polycrystalline panels have slightly lower efficiency, generally ranging between 14% and 18%. Their less homogeneous structure can slightly limit the flow of electrons. However, they remain a very viable option for many installations, offering good value for money. They are often recognisable by their mottled or bluish appearance, due to the presence of multiple crystals.
| Technology | Average Efficiency | Advantages | Disadvantages |
|---|---|---|---|
| Monocrystalline | 18 % – 22%+ | High efficiency, aesthetic, durable | Higher cost |
| Polycrystalline | 14 % – 18 % | Cheaper, good value for money | Lower efficiency |
In addition to silicon-based technologies, the market is evolving with the emergence of new technologies, particularly thin-film panels. These panels are manufactured by depositing a thin layer of photovoltaic material (such as cadmium telluride – CdTe, copper indium gallium selenide – CIGS, or amorphous silicon) onto a substrate. Thin-film panels have the advantage of being more flexible and lighter, which opens up new installation possibilities, including on less robust roofs or for integrated architectural applications. However, their efficiency is generally lower than that of crystalline panels, often ranging between 6% and 12%. Although their efficiency is constantly improving, they are still less common for conventional residential installations. Innovation in this area aims to improve their performance while retaining their unique advantages. It is interesting to follow their development for future solar installations.
The choice between these different technologies will depend on your priorities: maximising electricity production on a limited surface, optimising the investment budget, or seeking more flexible and lightweight solutions. It is always advisable to consult a professional to evaluate the best option for your specific situation.
Optimising your installation’s efficiency
To get the most out of your solar investment, several actions can be taken to optimise your installation’s electricity production. It’s not just about choosing the right panels, but also ensuring they function correctly in the long term.
Tips for a high-performing installation
A well-thought-out solar installation from the start is the key to optimal production. This begins with the choice of location and orientation. Ideally, panels should be oriented due south and tilted between 30 and 35 degrees to capture maximum solar radiation throughout the year. However, even a south-east or south-west orientation can yield excellent results. It is also crucial to ensure that the panels will not be subject to shading, whether from trees, neighbouring buildings, or other elements of your own roof. Using simulation tools can help anticipate these seasonal shadings. The choice of high-efficiency panels, such as monocrystalline models, is also a decisive factor. For an installation in Belgium, aiming for panel efficiency above 20% is a good strategy in 2025.
The importance of regular maintenance
Maintenance of your solar panels is often neglected, yet it has a direct impact on their performance. Dust, pollen, dead leaves, or even moss can accumulate on the panel surface, thereby reducing their ability to capture sunlight. A production loss of 2 to 8% per year is entirely possible if the panels are not cleaned. It is therefore recommended to clean them once or twice a year, ideally in spring and autumn. A simple cleaning with clear water and a soft brush or telescopic pole, performed from the ground if possible, is usually sufficient. For more complex or hard-to-reach installations, calling a professional is advisable. Regular maintenance helps maintain a good production coefficient and ensures the longevity of your system.
Solutions to improve existing efficiency
If your current installation isn’t producing as much as you’d like, there are solutions to improve its efficiency. Adding power optimisers, for example, can help compensate for losses due to partial shading or differences in performance between panels. These devices, such as those offered by SolarEdge, allow each panel to operate independently, thus maximising overall production. Another option is to switch to micro-inverters, which are particularly effective in low sunlight conditions. It is also possible to consider a more thorough cleaning if a significant accumulation of dirt is observed. The choice of choosing a power optimiser adapted to your existing system is a key step for significant improvement.
Efficiency in the Belgian context
The efficiency of solar panels in Belgium is a topic of great interest, especially with varying electricity prices. In 2025, understanding how it works here is essential for making a good investment. We can’t just look at catalogue figures; we need to see what it actually yields under our Belgian sky.
Average sunshine in Belgium
The average annual sunshine in Belgium is generally between 1,000 and 1,100 kWh per square metre. Some provinces, such as Limburg or parts of Hainaut, receive a little more sun. This has a direct impact on your installation’s total production. It’s important to know that in winter, production is much lower, representing only 15 to 20% of what can be obtained in summer. To get a more precise idea of the sunshine at your address, tools like PVGIS are very useful.
Criteria for good local efficiency
So, what constitutes good efficiency for an installation in Belgium in 2025? We generally talk about panel efficiency between 18% and 22%. But good efficiency is not limited to that. You also need to look at the relationship between the initial cost, the expected annual production over 25 to 30 years, and the price of electricity. A criterion often used is the cost per kilowatt-hour produced. To ensure you are dealing with reliable professionals, it is advisable to check if they have certifications such as QualiPV 500. This label guarantees that the installer complies with quality and reliability standards.
Profitability of solar installations in Belgium
The profitability of a solar installation in Belgium depends on several factors. The orientation and tilt of the panels play an important role. Ideally, a due south orientation with a tilt of 35° to 40° is the most efficient. If your roof is oriented east or west, expect a slight drop in efficiency, perhaps 10 to 20%. You also need to take into account performance losses that can be up to 10-15% due to inverters, cabling, or partial shading. Regular maintenance, such as cleaning the panels, is also necessary to avoid efficiency losses of 2 to 8% due to dirt. On average, a solar installation in Belgium can produce between 850 and 1,100 kWh per kilowatt-peak installed per year. Electricity prices, which can average 28 cents/kWh in May 2025, directly influence the profitability of your solar project in Belgium.
It is important not to rely solely on the nominal efficiency indicated in the laboratory. The actual efficiency on your roof will always be influenced by local weather conditions, temperature, and the natural wear and tear of the equipment over time.
Evaluating the efficiency of a complete system
Once you have an idea of the efficiency of your individual panels, it’s important to look at the complete picture: how the entire system works together. It’s not just a matter of panels; other elements play a role in the amount of electricity you end up using.
Calculating overall annual efficiency
To get an idea of your installation’s overall efficiency over a year, we use a formula that takes into account the total energy produced relative to the total surface area of your panels and the average annual sunshine in your region. The formula looks like this:
Annual Efficiency (%) = Energy produced (kWh/year) ÷ (Total panel surface area (m²) × Annual irradiance (kWh/m²/year))
It is important to note that annual irradiance varies depending on your geographical location. Using a solar simulator can help you get a more precise estimate for your specific address. This calculation gives you a measure of your system’s overall performance.
Taking system components into account
Several elements, beyond the panels themselves, influence electricity production. Losses can occur at different levels:
- Inverters: These devices convert the direct current from the panels into alternating current usable at home. Their own efficiency (often above 96%) has an impact.
- Cabling: The resistance of the cables can lead to a slight energy loss, especially if the cables are too long or of insufficient cross-section.
- Temperature: As mentioned previously, heat reduces panel efficiency. Systems that manage heat better, such as those with IBC cells, may have a slight advantage.
- Dirt and shading: Even partial shading or an accumulation of dust can significantly reduce production.
Overall losses ranging from 10 to 15% should be expected between the gross production of the panels and the electricity actually usable.
Impact of inverters and cabling
The inverter is an essential link in your installation. Its conversion efficiency, often expressed as a percentage, determines how much of the energy produced by the panels is actually transformed into usable current. A less efficient inverter means greater energy loss. Similarly, the cabling must be correctly sized. Cables that are too thin or too long create electrical resistance that dissipates part of the energy as heat. Choosing quality components and careful installation is therefore essential to minimise these losses and maximise the efficiency of your solar system. For a personalised estimate of your installation’s production, it is advisable to use an online simulator.
Evaluating the efficiency of a complete system requires looking beyond panel specifications. Every component, from the inverter to the cabling, plays a role. Understanding these interactions allows for better anticipation of actual production and optimisation of the installation for maximum performance.
Durability and efficiency degradation
Even though solar panels are designed to last for decades, their performance is not static. Over time, a slight decrease in efficiency is inevitable. Understanding these degradation mechanisms is essential for evaluating the long-term profitability of your installation.
Annual efficiency loss of panels
All solar panels undergo natural degradation, which leads to a gradual decrease in their ability to produce electricity. Modern technologies are designed to minimise this loss. Current panels generally show an annual efficiency loss of approximately 0.2%. This means that after 25 years, a panel can still produce between 80% and 85% of its initial power. It is important to check the guarantees offered by the manufacturer, which often specify this degradation rate.
Lifespan and long-term performance
The lifespan of a solar panel is generally estimated between 25 and 30 years, or even more for some high-quality models. During this period, the overall performance of the installation will depend not only on the intrinsic degradation of the panels but also on the quality of other system components, such as the inverter and cabling. A well-designed and maintained installation will maintain a satisfactory level of production throughout its lifespan. It is advisable to consult the technical sheets to know the estimated lifespan of your system components.
Choosing degradation-resistant panels
To ensure lasting performance, the choice of solar panels is crucial. Monocrystalline panels, for example, are often recognised for their better resistance to degradation compared to polycrystalline panels. Furthermore, certain cell types, such as heterojunction (HJT) or IBC (Interdigitated Back Contact) cells, show better tolerance to temperature variations, a factor that can influence long-term degradation. Prioritising manufacturers offering solid production guarantees is a prudent approach to ensure the longevity of your investment. It is also recommended to use certified installers for professional installation, which contributes to the longevity of the installation and allows you to sell surplus electricity under the best conditions.
The durability of your solar panels is important for them to continue functioning well. Over time, their efficiency may decrease slightly; this is normal. To learn how to keep your panels in shape and optimise their energy production, discover our tips on our website.
In summary: efficiency, a key measure for your solar installation
To put it simply, the efficiency of a solar panel is a bit like a car’s fuel consumption: it tells you how effective the equipment is at converting the sun’s energy into electricity. We’ve seen how to calculate it with a fairly direct formula, using peak power and the panel’s surface area. Remember that the figure you see on the technical sheet, measured in the laboratory, is one thing, but the reality on your roof can be a little different. Factors like weather, shade, or even heat can affect what you actually get. So, when you look at offers, compare efficiencies carefully, but also think about how your installation will be done and how it will be maintained. It’s by combining good basic efficiency with a well-thought-out installation that you’ll get the most out of your solar system in the long term.
Frequently Asked Questions
What is solar panel efficiency?
Solar panel efficiency is a bit like the grade it gets at school. It shows what proportion of the sun’s energy the panel manages to convert into electricity. If a panel has 20% efficiency, it means it uses 20% of the light it receives to make electricity. The higher this grade, the better the panel is at producing energy.
How do you calculate a panel’s efficiency?
It’s quite simple! You take the maximum power the panel can deliver, which is called ‘peak power’ (often written as Wp, like 300 Wp). Then, you divide this power by the total surface area of the panel, knowing that you need to multiply this surface area by 1000. The formula looks like this: Efficiency (%) = Peak power (Wp) / (Panel surface area in m² x 1000). For example, for a 300 Wp panel that is 1.5 m², the calculation would be 300 / (1.5 x 1000), which gives 20%.
What is peak power (Wp)?
Peak power is the maximum power a solar panel can produce. It is measured under perfect conditions: very strong sunlight (1000 W/m²), a pleasant temperature (25°C), and light that has passed through the air in a specific way. It’s a bit like a car’s top speed when tested on a special track. It gives an idea of its potential.
Why are monocrystalline panels more efficient?
Monocrystalline panels are made from a single silicon crystal, which makes the passage of electricity easier. It’s like having a clear motorway for electrons! That’s why they often have better efficiency, reaching 22% or more, compared to polycrystalline panels which are made of multiple crystals and can have efficiencies between 14 and 18%.
Does temperature affect efficiency?
Yes, absolutely! When it’s very hot, solar panels produce a little less electricity. For every degree above 25°C, efficiency can drop by about 0.4%. That’s why panels that are more resistant to heat, such as those with special technologies (HJT or IBC), are more interesting in hot regions.
Do solar panels need cleaning?
It’s a good idea to clean them from time to time! Dust, dead leaves, or pollution can settle on the panels and block some of the sunlight. This can reduce efficiency by 2 to 8% per year. A little cleaning, once or twice a year, can help maintain good electricity production.
Does a panel’s efficiency decrease over time?
Yes, a little. It’s normal for panels to slowly wear out over the years. They generally lose a small fraction of their efficiency each year, about 0.2%. But most panels are guaranteed to retain between 80 and 85% of their initial power after 25 years. Choosing good quality panels helps minimise this loss.
How do you know if efficiency is good in Belgium?
For Belgium, good efficiency for solar panels installed in 2025 is generally between 18% and 22%. Of course, this also depends on the exact location where they are installed, their orientation, and their tilt. The important thing is to see if the cost of the installation and the amount of electricity produced over the lifespan of the panels are worthwhile for you.
