PV-Anlage: Richtige Größe, Kosten und Wirtschaftlichkeit einfach erklärt

Is there a patented recipe to achieve the perfect size of a photovoltaic installation? What influence do the size of the photovoltaic installation and its type have on economic efficiency and, above all, on the independence of energy suppliers and what is the difference between the self-consumption quota? Consumption and degree of self-sufficiency? If you are interested, be sure to watch this video, it is worth it. Welcome to my channel, I'm finally Michael Zimmermann and in this video I would like to help. You will find the perfect size for photovoltaic systems Choosing the correct size is crucial for the efficiency and profitability of the system.

Whether you are faced with the decision as an individual or as a company planning a PV system for your customers, this is what matters. The video provides valuable tips and information. Let's explore the world of photovoltaic systems together and discover how to find the best possible size for your needs. Also talking about size. If size is not everything, we have to define some dimensions. This video, then on the one hand, is about photovoltaic systems for single-family or multi-family houses and we concentrate here in this video on the standard modules, which include the monocrystalline modules that currently have the best efficiency, the sizes of the modules vary from From manufacturer to manufacturer, with the same efficiency, but usually only in the centimeter range, today's modules are not only a little larger than before, but also much more powerful.

Just a few years ago, the modules were around 80 cm wide and 60 meters long. Powers from around 150 to almost 200 watts maximum. The efficiency of these modules and sizes ranged between 13 and 15 percent. Today, a standard monocrystalline module has a size of approximately 1.10 to 1.75 m and offers powers of up to 400 watts peak. Of course, there are also weaker modules, but there are also significantly more powerful modules of this size and the efficiency of this module is around 20%. A 20% water efficiency overall is certainly an interesting question. In Germany, solar radiation is on average 1,000 kilowatt hours per square meter and, of course, this depends on the location.

In the north, a module with 20% efficiency can convert one square meter of sunlight into about 200 kilowatt hours of household solar energy. In simple terms, this means that we can generate about 200 kilowatt hours of electricity per year. For a photovoltaic installation with a surface area of ​​one square meter, for 1,000 kilowatt hours we need about 5 square meters. For a roof surface of 4,000 kilowatt hours we need approximately 20 square meters and for 10,000 kilowatt hours, about 50 square meters of surface. However, the most important thing is that the module area is aligned to a certain extent with a slope of between 20 and 40 degrees and is relatively free of hardening, otherwise the performance will probably be slightly lower than the orientation and tendency towards the performance will be.

It is discussed again in a separate video, which would go completely beyond the scope of this, perhaps some additional information at this point should not be confused with kilowatt hours. By specifying the kilowatt peak we obtain the information The maximum power of a photovoltaic energy. The system is determined by determining this power under so-called standard test conditions. With one kilowatt peak you can generate around 1,000 kilowatt hours of solar energy per year, this also depends, of course, on the inclination of the module. the orientation and the absence of shadow in this case Approximately 2.5 modules with 400 watts appear exactly so 1000 watts are peaks so a kilowatt peak with 2.5 modules, according to this approach, we would generate around 1000 kilowatt hours of solar energy.

The modules are almost. two square meters in size, so for this calculation we go back to our five. By the way, you get square meters per kilowatt peak because you need building authority approval for modules larger than two square meters, which is why all modules are less than 2 m² The modules have evolved even further and are not only better than before, but they are also much larger. I remember very well that in the period of high subsidies for photovoltaic systems in the early 2000s, a photovoltaic system had everything in order and. The kilowatt hour peak costs between 4,500 and 5,5500 euros.

Today prices are about a third of the current price. Some will rightly say yes, previously the feed-in tariff was more than 50 cents per kilowatt hour. cents after the adjustment, even if we deduct the market brake, the proportion is no longer correct, each other is only 1/6 and that is why today it is no longer worth it. There are also these voices, it's okay except it's not worth it anymore. This is definitely not true. Previously, photovoltaic systems were based on a completely different business model: the business model was called full power, which still exists today, but is rarely used in residential buildings and, if anything, is only used in . combination, but then it was the standard because there was another business model.

System operators filled their roofs and everything was fully powered. Unlike today, the purchase price of electricity was also somewhat lower and therefore made no sense. all to use solar energy yourself and for this reason the question about the size of a photovoltaic system was answered very easily: the regulation of the size of the photovoltaic system was determined by the size of the roof or the available budget was regulated or both. Today there is a surplus injection business model and, unlike before, the photovoltaic installation is part of the building system technology and operators have the stated objective of using the majority of the electricity generated by themselves. and only the surplus, that is, electricity. which is not used at the time of generation, is injected and thus made available to the general public and hence the question of system size arises from other perspectives.

It is no longer a question of how much electricity you can sell, but it is only a question of how little you can buy with current electricity prices and current electricity consumption. Until recently, the entire method of consideration and calculation revolved solely around normal household electricity, that is, comfort electricity. On average, for a household of four people, Family at Sound builds 4,000 kilowatt hours a year, but electrification is part of the energy transition and therefore an important issue in our buildings and that is why we have to think about heating and mobility and in the two sectors in Yes, the future also means electricity and the heating of the future is the heat pump, the car of the future is the battery-powered electric car and this must be taken into account in current planning and that is why current electricity.

Annual demand can rise rapidly to current levels of 4,000 kilowatt hours to 10,000 kilowatt hours or more, meaning household electricity consumption has remained almost the same in recent decades, even though devices are much larger. efficient than the same level. With the increase in efficiency, the number of devices and, of course, their use has also increased. The electricity demand for the new heat pump heating of the future depends, of course, on the living space and, very importantly, also on the energy efficiency. If we take a building with a living area of ​​around 125 square meters and simply assume a heat pump electrical consumption of around 30 kilowatt hours per square meter, then we can also add an additional 4000 kilowatt hours per year.

In electromobility, we assume an energy consumption of an electric car of 20 kilowatt hours per 100 km, which is the average for a mid-range electric car and if we assume a mileage of 10,000 km per year, we can In our example, add another 2,000 kilowatt hours per year. From 4,000 kilowatt hours it can be seen that 10,000 kilowatt hours of electricity are needed per year and, as a photovoltaic system cannot normally be expanded so easily, the future electricity consumption of both must be calculated. heating and mobility sectors take it into account directly in planning As part of my energy advice, I am often asked about the topic of energy independence with the use of 100% of your own electricity;

This is the dream of many owners and to be honest, it's my dream too, but now maybe I'm becoming unpopular with one or the other. But unfortunately it is not that easy, at least not with a reasonable financial outlay, but if we could mathematically cover all the energy need with a photovoltaic. system, for example, with an electricity requirement of 4,000 kilowatt hours, that would be a four kilowatt plug system and an electricity requirement of 10,000 kilowatts would be a 10 kilowatt level system, electricity is also needed when the sun is not shines. The other side thinks. that on very sunny summer days the photovoltaic system prefers to consume more energy than we can use, so we constantly have excessive or insufficient coverage and, therefore, there is no balanced relationship between electricity consumption and supply of electricity through our photovoltaic system.

It has a certain basic electrical load, which is the amount of electricity that is required even if it does not need much grease to operate and runs 24 hours a day, even at night, early in the morning or later at night, it does not glow Sun. and then normal electricity consumption is added to this base load and by the way, who would have thought when the sun is not shining, then there is a manageable level of congruence between electricity production and direct electricity consumption, not all of them They are home during the day, that's the main thing.

On very sunny days, electricity production is much greater than electricity consumption. In winter, exactly the opposite happens. However, you must adapt your energy management to the production of electricity using a. dry or other electricity consumption under the sun. Breaking down the day, let's continue with our example with 4000 kilowatt hours per year, if we divide the 4000 kilowatt hours by the 365 days, we get an average daily consumption of around 11 kilowatt hours, but the electricity generated per day contrasts with the consumption. In January, a photovoltaic system generates relatively little, less than 2.5 percent of its annual electrical output, while in June the system shows its highest output at just under 15% with a four-kilowatt level system. and a year of 4000 kilowatt hours That is not even equivalent to 100 kilowatt hours of solar energy for the entire month of January, that means a little more than three kilowatt hours a day and in June it is almost 20 kilowatt hours a day and in the In In summer the sun also does not rise at night, which means we have the same problem as us.

This means that we are not independent of the energy supply and that contradicts our business model and now comes the point where we have to think about our independence. or rather our dependence we have to do the calculations, although the calculations at this point are exaggerated we simply estimate it or better yet, we have it estimated and the best way to do it is to go to the website of the University of Berlin. Applied Sciences, that is, HTW Berlin has a very good tool that lives up to its name and is called independence calculator for photovoltaic systems.

I'm linking the page here in the description. It is really a very interesting and very simple tool. It's very fun to experiment. Just try it. I can only recommend it. On the first page we find a new term called share of energy consumption which writes the ratio between electricity consumed and electricity generated. , less electricity is injected into the grid. With an annual electricity consumption of 4,000 kilowatt hours and a system size of 4 kilowatt peak, the self-consumption quota is 30 percent, which means that no more than 70% of the electricity generated is fed. to the grid If you consume 5,000 kilowatt hours of electricity per year and have a system size of 5 kilowatt peak, your own consumption will also be 30%.

With a different size of 6 kilowatts and a power consumption of 6,000 kilowatt hours, the 30% self-consumption quota remains the same even in small systems, as long as the power consumption and the system size are correlated with each other, this It also applies to the older ones. Systems like this with 10,000 kilowatt hours of energy consumption and a system size of 10 kilowatt peak do not change anything, the proportion of self-consumption remains at 30%. But be careful, the tool calculates with a little more than 1000 kilowatt hours per kilowatt peak, if the specific performance of the system is below the level, for example only 900 kilowatts, you have to take that into account and make the photovoltaic system a little larger in the respective proportion, then the self-consumption proportion will be adjusted again.

However, this only gives us theinformation that we really need in a limited way. We want to be as self-sufficient as possible and therefore as independent as possible from any energy. suppliers and for this we need the wheel of self-sufficiencyThe degree of self-sufficiency describes the relationship between the electricity consumed by oneself and the total electricity consumption and that is the level of independence that really concerns us according to our previous example with an annual electricity consumption of 10,000 kilowatt hours and a photovoltaic plant. With a maximum power of 10 kilowatts, the degree of self-sufficiency corresponds to the proportion of self-consumption and that remains the case.

As long as electricity consumption and PV performance are correlated, the proportion of self-consumption remains the same regardless of system size. , but what happens if electricity consumption remains at 10,000 kilowatt hours and photovoltaic production is reduced to 5 kilowatts peak, self-sufficiency increases to 24% and self-consumption also increases by 46%? Exactly what we don't want, what do you want? It seems that if we reverse it, when the PV system is suddenly twice the annual electricity consumption - you guessed it - self-sufficiency rises to 36 percent, self-consumption falls to 17 percent, that's better. But now I want to know, we are setting all the parameters to the same level again.

The annual electricity consumption is 5000 kilowatt hours, the photovoltaic production is 5 kilowatts and we are using a battery storage system with 5 kilowatt hours so that we can use a large part of the energy. base load and a certain proportion of normal electricity consumption outside the Discover the performance of our PV system and what happens Self-sufficiency increases to 56% and the proportion of self-consumption also increases to 59%. What happens if we increase electricity consumption to 10,000 kilowatt hours, the system to 10 kilowatt hours peak, and the storage to 10 kilowatt hours? You can already guess, here it also remains the same, the level of self-sufficiency is 56.%, and the proportion of self-consumption is 59% and that always remains.

So no matter the system configuration, as long as the three values ​​correlate with each other, it will remain that way. Yes, I know it's very boring and that's why. We change the parameters again with an annual electricity consumption of 5000 kilowatt hours and double the photovoltaic production with a peak of 10 kilowatts and configure the storage. At a peak of 10 kilowatts, self-sufficiency increases to 76% and the proportion of self-consumption increases to 51%. We observe that storage contributes to both self-sufficiency and self-consumption and if we now reduce storage to 5 kilowatt hours with the same electricity consumption and the same system configuration, self-sufficiency also falls to 63% and the self-consumption share to 33% and what it looks like if we do that Increase storage to 15 kilowatt hours, you may have already guessed that they increase both: self-sufficiency to 80% and self-consumption to 43%.

Time for a little time in between Conclusion that we have seen without a photovoltaic storage we can achieve an independence from the electrical grid of the order of around 30%, much more is not possible, in most cases it is even a little less, yes , with a storage system, a self-sufficiency of up to 80% is possible, but at most Depending on the size of the system, maybe a little more is possible, but the profitability is completely lost, but we will look at it more closely with a device of storage in a separate video, as I said, that would be completely beyond the scope at this point, so we have seen that if the electricity consumption and electricity performance are approximately equal, the degree of independence is around the 30%.

But we've also seen that our need for energy is distributed fairly evenly throughout the year. Let's leave aside the heating; Of course, it plays in a different league with PV system performance, but it depends a lot on the time of year. This is also not a secret problem and that is why the total performance of the system should in any case be greater than the annual electricity consumption. I recommend a factor of 1.3, it can also be 1.5. is better than need and how it works It is relatively simple: you take the annual electricity consumption multiplied by 1.5 and divide it by 1000 and then by the available modules and then we round up or down and if the specific electricity output is less , then you divide system specific is only 900 kilowatt hours. per kilowatt peak, then we would get a letter system size of 6.6 kilowatts.

But keep the six kilowatt peak, divide it by the 400 watt modules, that's 15 modules and you can achieve a self-sufficiency of 34% and a self-consumption quota of 22% - you guessed it - this value also remains the same with The same relationship between the annual electricity consumption and the performance of the photovoltaic system is also relatively boring, but what the economic efficiency looks like with these parameters and we will see it now with peace of mind and comfort: it is best to have a coffee. Currently the price of electricity is 35 cents per kilowatt hour, the feed-in tariff is just 8.2 cents per kilowatt hour.

It is clear how uninteresting the injection of electricity is compared to self-consumption. PV system costs are negotiated differently depending on size, and for a system size of 6 kilowatts maximum, let's simply set a beep kilowatt price of €1,500. It costs around €9,000 without any major intervention in the electrical installation or other environmental measures. The energy costs without a JAPV system in this example amount to 4,000 kilowatt hours for 35 cents, i.e. €1,400 per year via the photovoltaic system. We cover 34% of the electricity need, that is, 1,360 kilowatt hours for 35 cents, or 476 euros per year, but the system produces 6,000 kilowatt hours of electricity, so there are still 4,640 kilowatt hours that we sell at 8.2 cents per kilowatt hour and that results in a performance of 380 euros together with the savings of 476 euros, this results in a total of 856 euros that we can deduct from the €1,400 of energy expenses and therefore the new expenses of annual energy is not 1,400 but only 543 euros if we divide the €9,000. system costs for the claim of €865.

We then get a payback period of around 10.5 years, so now we do the same calculation again for an annual electricity consumption of 10,000 kilowatt hours. Here we can set the factor a little lower, say 1.3. Therefore, the size of the photovoltaic system will be 13 kW. But be careful, we need at least a net available roof area of ​​71 square meters. With this size a slightly cheaper system price can be generated. We simply assume 1,300 euros per kilowatt peak. , which means that according to this calculation the system will cost €16,900 with 10,000 kilowatt hours of electrical consumption, the electricity costs are €3,500 per year of the €3,500 we can save 34% with the photovoltaic system, we have seen it, so a total of €1,190, that is, a total of 3,400 kilowatt hours of electricity that we do not have to buy, but the system produces a total of 13,000 kilowatt hours of electricity per year minus the 3,400 kilowatt hours of personal use, there are still 9,600 kilowatt hours left and we can sell them, so we multiply the 9,600 by 8.2 cents per kilowatt hour, which results in €782 in feed-in tariffs, so the photovoltaic system generates a total of 1,190 + 782, that is, €1,873 per year that Now divide the system price of 16,900 by the €1,873 savings and that results in a payback period of approximately 9 years.

I omitted the numbers after the decimal point and, for simplicity, I have no interest but no increase in price. electricity costs But both are not unimportant parameters, if, for example, the price of electricity increases, the economic efficiency of the photovoltaic system automatically increases. Wow, I found a lot of numbers now and that's why we called it a day. For today, as I said, first I wanted to add the storage system, but that's the point here, completely the framework and that's why we are making a new video, but again we promised with the same detail here some more comments, the only ones irrefutable .

The constant in this performance is the feed-in tariff and this is nominally 8.6 cents per kilowatt hour minus the 0.4 cent mobile market premium. That's why I assumed 8.2 cents in the calculations, that's what you really pay, the 35 cents electricity cost per kilowatt. hour are an average value, I have heard of much higher prices but also some lower prices. The system prices set per kilowatt peak are average values, so please, they are not set in stone and should therefore be treated with caution. I do not want to awaken false desires among interested parties nor do I want to make annoying offers because the price is supposedly too low or perhaps too high.

A photovoltaic location depends, of course, on many parameters, including the quality of the materials, but also synergy effects on construction sites, scaffolding, new discoveries, roof renovation, etc. In calculating profitability, by the way, I assume net prices. From 2023 there will be no VAT for private network operators up to 30 kilowatts peak. I already made a video for this, I'll link it in the description, but you can also watch it again here, as nice as our simple HTW tool is, we don't see any individual power consumption profiles taken. note here Use this tool with caution. Homeowners who are away from home all day may not reach 34% self-sufficiency.

With a home office, they may even be able to generate higher independence values. The tool always calculates the same value. Regardless of the orientation and tilt of the module, an annual output of 1024 kilowatt hours per kilowatt P to the customer may be the case, but does not have to be true. In a new video we will see the influence of the inclination of the module. and roof orientation I will also explain why purely south-facing roofs are suitable for the new surplus feeding business model. Not so optimal are a little spoiler at this point from east to west, that's the new south, so stay tuned.

Okay, but I think I still owe an answer. What is the optimal system size? There is no such thing as my advice, just fill the roof because the energy transition takes place on the roof. If you liked this video, I'd be happy to get a thumbs up. above and if you want to hear more, subscribe to this channel, press the bell until next time, finally Energiewende your Michael Zimmer