Solar systems and photovoltaics: These are the questions people ask most frequently

by Dominik Zarychta on 01/05/2022

Eloi_Omella/Getty ImagesBefore purchasing a solar system, many questions arise, we have the answers.

With the significant rise in electricity prices at the latest, many homeowners or builders are considering it to buy a solar system. Our solar webinar will surely answer many of your questions. Although it took place in mid-November, we have summarized the questions from the more than 1,300 viewers here.

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Click here for the recording of the solar webinar

What funding options are currently available for solar systems and energy storage?

Meanwhile there are only three federal states that support the purchase of an energy storage system: Berlin, Bavaria and North Rhine-Westphalia. In November, however, the Free State of Bavaria had temporarily suspended an application. But do not despair - even if there is not another subsidy in every federal state, some cities and municipalities still offer some. However, while the federal states usually subsidize the storage systems, cities promote the individual solar modules. It is always worth asking in your own city.

Can you expand a solar system at any time?

Our solar provider test showed that hardly any provider can expand the existing solar system. Most of the time it is due to old components that are no longer compatible with newer ones. You should also not ignore the additional costs that arise from an extension: from a new framework, the cabling (string planning), the delivery to the assembly, there are very high extra costs. These are usually disproportionate to the result.

An alternative would be to set up a new solar system with an independent inverter on an extra area such as a carport. From an economic point of view, this option is much more worthwhile than expanding the old solar system.

Are there roofs that make it impossible to install a solar system?

Depending on the provider, not all roof constructions can be covered. The most difficult are mortared roofs and roofs with cardboard pads. The provider zolar, for example, cannot offer a solution for either of the roof structures. If you are affected by this, you can only look for a solar technician who specializes in these roof constructions.

But there are also other special cases in which the solar installation is not possible with every provider. For example, Zolar does not offer its services for pitched roofs with bitumen, as tightness can no longer be guaranteed here. Again, you should look for a specialist.

A solar system on your roof is also never possible if you have over-rafter insulation with a bitumen membrane above it. The above-rafter insulation sags over time, as water can penetrate the bitumen membrane when drilling. Added to this is the high weight of the solar modules.

Also make sure your roof doesn't need a major repair for the next 20 years. It is better to renovate the roof beforehand, so that you have lower costs in the long run. In any case, before installation, the statics of the roof will be checked, in which possible repairs can be uncovered.

Does an in-roof or an on-roof solar system make more sense?

In contrast to in-roof solar systems, on-roof variants do not lie directly on the roof, but rather hover a few centimeters above it thanks to a frame. The biggest difference between the two designs is primarily the look, because in-roof systems fit better into the overall picture of a house and are not so noticeable. Technically, however, these are the same panels. However, there are other points you should consider. With in-roof solar systems, it can sometimes get a little warmer under the roof, with on-roof systems the opposite is the case. Due to the air circulation between the roof and the modules, the room temperature cools down more quickly. Apart from that, there is a tax difference between the two solar systems.

Patrick Pleul/dpa-Zentralbild/dpaThe differences between in-roof and on-roof solar systems are minimal. Here your personal optical preference decides. Our solar system purchase advice The large solar system comparison. The best providers at a glance. Find out now! Our solar system purchase advice The major solar system comparison. The best providers at a glance. Find out now!

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Should I use optimizers in the event of shading?

It is well known that solar modules that are in the shade produce less electricity. In order to still get the maximum out of it, there are so-called performance optimizers. With the help of such a device, the individual solar modules are kept at their maximum power point (MPP) for as long as possible, thus compensating for the power loss.

In general, the optimizers drive up the investment costs and make the modules more susceptible to technical damage. You should therefore make sure to avoid shading as much as possible before starting construction.

If shading cannot be avoided, you should ensure that the module optimizers harmonize with the entire system, such as the inverter. This is important because the modules are connected in series. If a module can no longer generate electricity due to shading, it can be heated up by other solar parts in the row and thus damaged.

How fireproof are solar systems?

Overall, there are few known cases in which a solar system has caught fire. This was also confirmed by the Fraunhofer Institute for Solar Energy Systems (ISE) in a study. According to this, less than 0.006 percent of all solar systems caused a fire.

If a fire does break out, there is a good chance it can be contained quickly. Firefighters in Germany now receive extra training and can react quickly. If you still want to be on the safe side, you can call your building insurance company and ask whether your solar systems are already insured. In some cases, these are already included in the basic insurance.

Can the electricity generated be sold to tenants?

If you rent out the apartment or house on which the solar system is located, you can also sell the electricity. There are several options: For example, you can set a flat rate for electricity in the rental agreement. Another variant is to check and bill the electricity using a meter. But beware! Be careful not to get too involved in the commercial space. This can lead to tax problems.

Can the wall box be connected to the solar system?

There are currently only a few compatible systems that enable intelligent charging. Therefore, when buying a solar system, make sure that the system can be combined with the wall box. All state-sponsored wall boxes have a connection that allows control. However, the legally mandatory control consists only of an on and off button. For a connection to a solar system, this is not enough. The few wall boxes can be controlled even more individually. The energy management of the solar system would have the option that you could regulate the energy supply individually.

It is best to buy the system together with the wall box to exhaust all possible options. If you already have a wall box, you should look at the solar system to see which components from the solar provider the charging station fits with.

Photo: Rolf Haid/dpaWhat should you know before installing a solar system? EFAHRER.com has the answers. Which solar system provider is the test winner 2021?" Find out now about the EFAHRER test results! " Which solar system provider is the test winner 2021?" Find out about the EFAHRER test results now! "

When does energy storage make sense?

An energy storage device is always worthwhile for you if you are not at home all day and cannot use the electricity produced immediately. We advise against a home storage system only for the night.

An energy storage device currently costs around 500 to 700 euros – per kWh. Assuming a normal service life of 15 years, electricity from 3,750 charging cycles of the solar system is fed into the energy store. In one year, about 250 charging cycles in the storage tank are possible with the solar system. If you buy a 1 kWh energy storage device for 500 euros, 3,750 kWh will be channeled through the storage device in 15 years.

If you offset this bill against the electricity price, you would be at the current German electricity price that you will spend on energy storage over the 15 years. However, the storage would still have been worthwhile in 15 years, as there is a high probability that electricity prices will rise in the next few years.

If you are unsure whether you want an energy storage device, you can also buy it later. For example, most solar system providers offer energy storage in the minimum configuration with a capacity of two kWh, as well as an energy storage system that can control this storage. Later, if you are interested, there will be modular expansion options that allow the energy storage to be expanded.

Can the energy storage device also be in the attic?

Most of the storage devices can be installed in the attic, but you must obtain information from the manufacturer in advance, as there are exceptions. In addition, the correct operating temperature must prevail in your attic and frost must not form under any circumstances.

Also note that the energy storage can be very heavy. A 5.1 kWh battery weighs around 130 kilos and puts an extreme strain on floors and walls. And of course you have to heave such a chunk under the roof first.

Can the storage battery be placed in a detached garage?

Similar to the attic location, it depends on the storage model. So you have to pay attention to the manufacturer information again. For example, you can mount Tesla battery packs outside on the outside wall of your house. Solar consultant Kai Stöckmann also gives the tip to install a small, insulated wooden construction in the detached garage, which insulates the power storage from the cold. But beware! The storage still needs enough space for air circulation. So avoid burying it in the ground, for example.

In general, the storage location should be planned in such a way that it is always exposed to your own “feel good temperature”. While lithium-ion batteries are slightly more tolerant than cobalt batteries, they should never be exposed to freezing temperatures. If the power storage is more cold-resistant, it heats itself up above a certain temperature. However, keep in mind that this process also costs energy.

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Which solar system provider is the test winner?

All questions have been answered and you now want to buy a solar system? Then all you need is the right provider. EFAHRER.com tested nine providers active throughout Germany with six sample cases. The differences are huge, the test winner is clear.

Here you can find the big solar system provider test

Solar providers in the EFAHRER test: How the nine companies fared

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Rank	Provider	Rating	Website (20%)	Range of offers (20%)	Process (20%)	Consultation (40%)	Link
1.	Zolar	very good (1 ,3)	1.0	1.8	1.0	1.4	To the provider
2.	EON	good (2.0)	2.2< /td>	2.3	1.8	1.8	To the provider
DZ-4	good (2.2)	1.6	4.6	2.8	1.0	To the seller
4.	Clear solar	good (2.2)	3.8	3.7	1.5	1.1	To the provider
5.	Wegatech	good (2.3)< /td>	1.3	1.0	2.6	3.3	To the provider
6.	Sveasolar	good (2.5)	1.4	2.2	2.0	To the provider
7.	Yello Solar	satisfactory (3.1)	2.6	3.7	4 ,8	2,1	To the provider
	Enpal	-	2.7	4.6	3.1	-	To the provider
	Entega Plus	-	1.3	2.3< /td>	-	-	To the provider