Solar plug: Solar Energy from the Balcony Directly into the Outlet – Part 2

18 September 2023

6. What are the advantages of the solar plug-in module? Is it feasible for me?

*south / *east

By connecting a solar module to the grid, you make your personal contribution to the energy transition. Mini solar systems typically produce enough electricity to cover a significant portion of the base load on sunny days and of the peak household load during midday hours.

A single standard 380 watt solar module installed on a south-facing balcony with no shading provides around 280 kWh of electricity per year. This reduces your electricity consumption by about the same amount, as if you could have used the electricity directly in your household.

This energy volume is roughly comparable to the annual energy utilization of a fridge and a laundry machine in a household of two individuals. At an average electricity price of 33 euro cents, this results in annual savings of around EUR 66.

A single standard solar plug-in module usually costs in the EUR 350 and EUR 600 range. Due to very high demand and components supply chain disruptions, prices are significantly higher in certain cases. In contrast, however, household electricity costs have also increased significantly in recent months.

The module yield, hence its cost-effectiveness, depends on a range of diverse factors. These include the cost of purchase, optimizing module solar exposure, and current costs of electricity from the utility provider. It's particularly advantageous to have the vertical fitting on the outside of the balcony railing, facing from southwest to southeast, devoid of any shading. Vertical placement reduces peaks of unusable production in summer and increases usable yields in winter.

For a location in Germany with average sunshine times, you can estimate the cost-effectiveness of a solar module using a Solar Plug-in Simulator HTW Berlin evaluation.

Not only are you reducing your energy bills, but you're benefiting the environment. The minisolar system saves about 2.5 tonnes of CO2 emissions over 20 years. 

Unsuitable locations for installation:

  • behind the balcony railing, in the balcony niche;
  • on the wall below the upstairs balcony;
  • Places in the shade of trees, light poles, or adjacent buildings.

Permanent, or even partial shade, or module contamination can lead to a reduction in yield that is significantly more noticeable than with a PV system. You should, therefore, regularly check and clean the module .

Increasingly, municipalities, individual federal provinces and regional unions are supporting solar modules for connection to the grid through subsidies. Additionally, grid operators and electricity providers are progressively facilitating this application by streamlining the registration process and fostering, rather than obstructing, the adoption of such systems. Be careful! Subsidies often have prerequisites, such as the use of a special power socket, inspection of the electrical installation by an electrician, or covering the costs of a new electricity meter. To avoid issues with subsidies, please ensure these points are covered. 

When solar modules are integrated into the grid system, the feed-in tariff imposed by the Renewable Energy Act typically doesn't apply. If, for example, a solar module produces 500 kWh of electricity per year and 150 kWh of this goes into the grid, this means a feed-in tariff of around EUR 12 per year. This is countered by the regular but disproportionately high meter reading and billing costs.

In Regulation 2016/631, the European Union classifies small generators below 800 watts as “insignificant” as they “have no systemic importance”. However, German grid operators require that all power plants be registered with them, regardless of output capacity. However, the activity is not dependent on the permit. They have included this requirement in the relevant regulation (application rule VDE-AR-N 4105). A simplified form is provided for AC generators up to 600 watts, which includes grid plug-in solar modules, as per our definition. Completing this form does not require an electrician; you could do it yourself, if you use a plug-in solar module.

Many grid operators provide simplified forms on their website, and some send them upon request. Some even offer easy online registration. The registration must be accompanied by a data sheet of the inverter used, showing that the device meets the requirements for connection to the grid (declaration of conformity).

Some manufacturers of balcony modules offer to assist with the registration process.

Although it is disputed whether grid-connected solar modules are “installations” at all, at least insofar as these systems do not have a fixed connection but are plugged into the electrical circuit via a plug, same as household appliances, the Federal Network Agency also requires registration with the Market Data Master Registry.

These registrations offer no advantages to consumers, they only create bureaucratic obstacles. As a grid plug-in solar module is formally also a grid-connected PV system, registrations are required. A fine may be imposed for failure to register on the Market Master Data Registry.

Instructions: If you already have a roof photovoltaic system, which is older than 12 months, and the power generated by it is partially used in the household, the solar plug-in module is considered an additional new system. If not installed on the same roof (facing the same direction and at the same slope), the grid operator will most likely require an additional electricity meter. Under these circumstances, the operation of the solar plug-in module becomes unprofitable. Registration of the solar module with the grid operator and the Market Master Data Registry as an extension of the existing installation is only permissible if the rooftop installation was commissioned less than a year ago.

Even if solar modules are designed for self-consumption and not to feed the grid, electricity can still flow into the grid. Technically this is not an issue, and it is allowed if you use inverters that meet the standard.

Due to the solar module plug in, conventional meters with mechanical rotating pulleys (Ferrari meters) may start operating in reverse, as these meters are not equipped with a limiter. Therefore, in this case, the grid operator, as the operator of the main metering point, substitutes the conventional meter with a modern electronic meter, which is also known as modern metering equipment (mME).

These meters are available in two versions: One-way meters continue to measure only electricity consumed and do not read back when electricity is fed into the grid. The (small) excess power is not measured with this meter option.

The second option is a bidirectional meter. These are, technically, the same meters, but they are programmed to separately record and display both metering directions – the electricity drawn from the grid and the electricity fed back into the grid. Such meters are also used for photovoltaic systems with surplus energy.

Lawmakers anticipate that in the upcoming years all current electric meters in Germany will be superseded with such sophisticated meters under the initiative known as the Introduction of Smart Meters. 

The electricity grid operator is not allowed to charge you for removing the old meter and installing a modern metering device instead. This is because the Meter Operation Act provides that the cost of installing and removing meters must now be contained in the annual metering charge. Many grid operators agree to waive the meter bill as soon as a solar module is registered.

If modern metering equipment is installed, the annual metering costs can rise to the statutory maximum of EUR 20 per year.

Ensure that your chosen power utility company or the main power utility company does not double-charge you for metering costs as part of the basic electricity purchase price.

You should only buy devices that are ready to plug in.

On a technical note, it is really important that the inverter included in the set has a declaration of conformity according to VDE AR 4105, as this is the only way to use it in the power grid. Also, ensure that the inverter is limited to a maximum power output (alternating current) of 600 watts (AC). Solar modules may have higher power output.

In some cases, for example, companies sell devices with open cable ends without connecting plugs. Obviously, customers then have to install the plug themselves.

This is how manufacturers let the buyer shoulder the responsibility for final product implementation. Legally, however, this can only be done by a qualified electrician, not someone without specialist knowledge. The same is true for socket replacement: This should also be carried out formally by a qualified electrician.

Consumer Centers recommends, when purchasing, that you make sure solar module manufacturers have complied with the DGS safety standard (DGS 0001:2019-10) for connection to the grid. A product standard for grid-connected solar modules is expected in 2024. It is currently under development.

Mini solar systems, also referred to as balcony power plants, can sometimes be purchased from local specialized photovoltaic dealers. However, most offers are available in specialist online stores. An overview of the markets on this topic can be found on these websites:

  • PV Magazine (Photovoltaics Trade Magazine)
  • (German Solar Energy Society)

In the meantime, deals are also available in discount stores or electronics markets. However, they are usually much more expensive than specialist commercial offers, and the advice and choice within them is quite limited. Ensure that the quotations are technically comprehensive and include substructure, as an example.

If all the requirements are met, you can turn on the device yourself. Assistance can be found in specific areas from DIY workshops conducted by community energy cooperatives or different initiatives, as well as from local residents who have prior experience with solar panels.

Solar modules or modular inverters themselves do not directly indicate functionality or current performance. Inverters sometimes have an LED that signals certain operating states by flashing or glowing. However, this is not enough to determine whether the device operates properly and what its performance is.

Some inverters include a power measurement that you can read and save using an external auxiliary device. This can also be done through an online connection to a web portal, similar to photovoltaic systems (monitoring). Then energy output can be partially metered through a mobile device. 

If the appliance is connected to the outlet via a Schuko plug – provided this is allowed for the appliance you purchased – you can use a commercially available meter to plug in between the outlet and the refrigerator to determine power consumption. Many of these devices can also measure in reverse, thus they are also suitable as a power generation meter for a solar module.

Smart sockets operate on the very same principle; they can be switched on and off via WLAN from the router or from the smart home controls, and they often include energy metering.

Both meters and smart sockets are not yet available for connection via the so-called special connector Wieland. In this case, a small electronic device can be installed in the socket to collect the data. These electronics also measure the electric current flow and sends the data via Bluetooth or WLAN to the internet router or smartphone.

When solar modules and inverters have reached the end of their lifecycle, you can take them to your local recycling center or point of sale for disposal and recycling.

  1. Are local conditions suitable for connecting a solar plug-in module? Does this site have maximum solar exposure?
  2. Are the installation site, socket and circuit state-of-the-art?
  3. Does the landlord or the community of owners agree?
  4. Do potential restrictions exist under building or statutory law, as an example due to listed building regulations, in the case of an old town center or top glazing?
  5. What are the requirements of the network operator and the potential subsidizing authority?
  6. Did you find the right offer to meet all of your requirements? (equipment, price/quality, delivery, installation and connection, DGS safety standard/standard for future devices)
  7. Have you considered monitoring in order to check effectiveness?
  8. Do you have experts on hand or a local DIY group to turn to when in doubt?
  9. Is everything clear with the registration and required meter change?

This content has been prepared by the North Rhine-Westphalia and Rheinland-Pfalz consumer advice centers for the Federation of German Consumer Organisations (VZBV).

Source: Steckersolar: Solarstrom vom Balkon direkt in die Steckdose


This project is part of the European Climate Initiative (EUKI). EUKI is a project funding instrument of the German Federal Ministry for Economic Affairs and Climate Protection (BMWK). The EUKI competition for project ideas is run by the German Society for International Cooperation (GIZ). The overall objective of EUKI is to promote climate cooperation within the European Union (EU) in order to reduce greenhouse gas emissions.
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