Build your own balcony solar system with storage tank

A balcony solar system is primarily used to generate your own electricity and helps to cover the base load. Energy that is not consumed flows into the public grid without reimbursement. A balcony power plant with storage can store the surplus energy and make it available again when required.

Here you can find out whether a balcony power station with or without storage makes sense for you, how much electricity you can generate with it and whether the purchase can be subsidized.

Advantages of balcony power plants

Why is a balcony power plant a sensible investment?

• Contributes to covering the base load electricity costs, which in turn makes you less dependent on your electricity supplier
• Pays for itself relatively quickly - depending on the device and weather conditions, it usually takes between 3 and 10 years for the purchase costs of the balcony solar power plant to be amortized
• After amortization, the balcony power plant continues to generate electricity and thus ensures long-term cost savings
• Generates environmentally friendly electricity - reducing your own ecological footprint

→ Order Victron storage for PV balcony system as a set

How does a PV system on the balcony work?

A balcony solar system is usually made up of one or two photovoltaic modules with an output of 300 to 600 watts. The connected inverter converts the direct current generated into alternating current, which is used by the standard consumers in your household. The inverter is connected to a household socket using a mains cable.

The electricity generated by the solar system then flows into your household grid and can supply the individual consumers. For a balcony solar power system with storage, you need a special inverter, ideally a communication device and batteries.

When is a balcony power plant with storage worthwhile?

As the output of balcony power plants is relatively small compared to classic PV systems on roofs, the aim of a balcony PV system is not to supply the entire house, but to reduce your own electricity costs and contribute to a better ecological footprint.

The savings depend on how high your electricity consumption is and how high the yield of the solar system is. But as a rough estimate, you can achieve a self-sufficiency rate of around 10 to 30%. By storing surplus energy, you can also use the electricity when the sun is no longer shining. With this option, the feed-in to the public grid is reduced to a minimum without the need for reimbursement.

If your balcony is not facing the right direction, you can also install the solar system on the ground, on a flat roof, on your terrace or in the garden. The electricity yield is slightly higher if the system is positioned at the ideal angle to the sun and is not mounted vertically on a wall or your balcony.

Scientists at Rosenheim University of Applied Sciences and employees of the German Society for Solar Energy (DGS) have determined the level of electricity yields on different balconies in Rosenheim and have come to the conclusion that more electricity is produced if the module is not mounted vertically, but at an angle on a frame. A solar module works most efficiently when it is aligned to the south and positioned at an angle of 36 degrees from the ground. (Source: German Society for Solar Energy)

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Storage or feed-in - advantages and disadvantages

Balcony power plants are usually operated without a storage unit up to a maximum output of 600 watts. A major advantage is that you can generate your own electricity and thus reduce your electricity costs. Furthermore, installation is usually uncomplicated, which is why many private operators put a balcony power station into operation completely on their own.

However, there is one major disadvantage. Without a storage system, the energy generated must always be consumed immediately. Surplus energy is fed into the public grid without reimbursement. So if you regularly generate more energy than you consume, investing in a balcony PV system with storage can be worthwhile. Whether this is worthwhile depends on other criteria, of course:

• How much electricity can be saved with a storage system?
• How high are the acquisition costs for a balcony solar system with storage?
• When do the storage systems start to pay for themselves?
• What service life and manufacturer's warranty can be expected for storage systems?
• In Germany, can you expect to save any money at all by buying a system with storage or is this a losing proposition?

How much electricity can you save with photovoltaics on the balcony thanks to storage save?

The Berlin University of Applied Sciences offers the Independence Calculator, a practical online tool for estimating the degree of self-sufficiency and the proportion of self-consumption.

Using the example of a household with an annual electricity consumption of 2,500 kWh, we have drawn up a sample calculation for you to show the financial benefits with and without storage.

Our household uses two modules with a total output of 600 Wp or 0.6 kWp (kilowatt peak). For the variant with storage, we have used a battery storage of 1000 Wh (1 kWh) as a basis.

Our comparison clearly shows that the self-consumption share of the balcony solar system with storage is slightly higher. In our example, the degree of self-sufficiency increases by 7%. If we consider the annual electricity consumption of 2,500 kWh, the balcony power plant with storage results in a saving of 175 kWh. At a current electricity price of approx. 0.40 euros/kWh (as of 03/2023), the annual saving is 70.00 euros. With the current development of electricity prices, it is more likely that the annual savings will remain constant or increase.

However, our example can only provide a rough estimate, as the reality is often different. As a rule, German households consume significantly less energy during the working week. If you spend 9 hours of the day at work and only run the basic consumers at home, most of the energy generated goes back into the grid without being reimbursed. With a sufficiently dimensioned storage system, you can use the generated and stored energy when it is actually needed. The less energy you can consume directly, the greater the benefit of storage.

When does a balcony power plant with storage pay for itself?

As shown in our example, a household with an annual electricity consumption of 2,500 kWh can save around 70.00 euros compared to a system without storage. The acquisition costs for the storage modules including batteries are currently around 1,900 euros, which leads to a sobering amortization period of around 27 years. The maximum service life of battery storage systems is currently estimated at around 20 years, and the manufacturer's warranty is usually far shorter. At first glance, this does not look like a worthwhile investment. We have not taken other parameters such as maintenance, servicing and efficiency losses of the storage system into account in our estimate. The actual loss amount is probably even higher.

However, our calculation example can only provide an imprecise estimate. If you are rarely at home during the day and only the basic consumers in your household are running, then significantly more energy remains unused. In order to store this energy and use it later, you need a storage system. A well-coordinated system can have a positive impact on the profitability of the system.

Equipping a balcony power plant with a battery - how it works

To retrofit your solar modules with a storage system, you usually have to replace your inverter and - depending on the desired efficiency - install system components for monitoring.

We recommend a Victron Energy bundle, which is ideal for upgrading your solar modules. Components of the bundle are the MultiPlus 12/800/35-16 (combination of inverter and charger), the Cerbo GX-S (communication center), Energy meter EM 24 (energy meter), SmartShunt (battery monitor), Interface MK3-USB and connection cable. You will also need the appropriate batteries.

With this solution, you also have the option of directly connecting an end consumer for emergency power. This could then be used to operate a heater or the internet connection, for example.

→ Order Victron storage for PV balcony system as a set

How big can my balcony solar system be?

The maximum permissible output power of 600 watts is important for the operation of a balcony solar power system, as the legislator has created simplified registration procedures for this. The inverter converts direct current into alternating current for each system. The loads in your household are all operated with alternating current.

In order to prevent overloading and thus overheating of individual cable harnesses, most inverters for mini PV systems have an output power of less than 600 watts. If this is not observed, house fires can occur in the worst case.

How can I get a subsidy for my balcony power plant?

There is no state subsidy program for balcony power plants, but the opportunities for subsidies for private operators of environmentally friendly mini PV systems are currently growing rapidly. More and more cities and municipalities are offering subsidy programs through which you can apply for grants of various amounts. The amount of funding varies greatly depending on where you live and can range from 50 to 1450 euros.

Some subsidies are paid as a lump sum per system, while others are linked to the solar power. In any case, find out in advance about the applicable application deadlines and whether the application must be submitted or approved before the purchase. As a rule, a subsidy must be approved before the balcony solar system is purchased.

Some cities also often specify a period of 10 to 15 years during which the balcony power plant may only be used in their district. Moving to another city therefore becomes a problem. Most subsidy programs for balcony power plants are limited to a maximum output of 600 watts.

In February 2023, for example, there are numerous funding opportunities for residents of North Rhine-Westphalia, ranging from 100 to 800 euros depending on where you live. In most cases, there is even a lump sum that is paid out even if only one solar module is used.

Heidelberg residents currently benefit the most from the subsidy programs in Germany. Holders of a Heidelberg Pass can receive subsidies of up to 1,450 euros with a personal contribution of 50 euros. These city passes or ID cards are not uncommon, so enquire locally and ask specifically about them.

How many balcony power plants are allowed?

There is no legal limit for balcony power plants per household in Germany. However, the inverter may not feed in more than 600 watts and a maximum of one power generation system may be operated per final circuit. The limit of 600 watts applies to the sum of all systems. You can usually tell how many circuits you are allowed to have in your apartment or house by looking at your fuse box.

Guerrilla PV and balcony power plant: what do you need to know?

What does the term guerrilla PV mean? Normally, you have to register your balcony solar devices with the grid operator and in the market master data register and the professional installation must be carried out by an electrician.

As most systems can be connected to standard household sockets, people often install them themselves. However, the risk of damage lies with the operator. If you still decide to install the system yourself, please note the following points:

Are guerrilla balcony power plants punishable by law?

In principle, balcony power plants also fall under Section 9 Paragraph 2 of the German Renewable Energy Sources Act (EEG). This paragraph stipulates a reporting obligation for solar power systems.

If you do not register your mini PV system in the Federal Network Agency's market master data register, you are committing an administrative offense. This can be punished with a fine of up to 50,000 € in accordance with section §95 of the Energy Industry Act.

In practice, however, the penalty is significantly lower and to date we are not aware of any case in which the grid operator has taken legal action against a mini PV system operator.

Attention: Since the summer of 2022, new regulations have come into force that include additional penalties for operators of non-compliant solar installations. These include, for example, systems that use incorrect electricity meters, do not have compliant inverters or generate more than 600 watts of power. The amount of the fines depends on the total output of the solar modules.

Here is an example: If your balcony solar system consists of two modules with an output of 300 watts each, the monthly penalty payment would be 6 euros. At 72 euros per year, this would of course have a significant impact on the profitability of your system.

Many experts assume that most balcony power plants in Germany are not registered. Meanwhile, it may be difficult for the grid operator to identify them, which makes it very unlikely that penalties will be enforced. If you don't want to take any risks, it's best to register your system before commissioning.

→ Order Victron storage for PV balcony system as a set