June 16, 2025, 10:30 am | Read time: 4 minutes
Balcony power plants can be worthwhile, such as for supplying part of your household with solar energy. However, not all plug-in solar systems perform well in tests. “Stiftung Warentest,” a German consumer organization, uncovers several deficiencies.
Balcony power plants are designed to generate electricity and help save money–at least as long as the sun is shining. They may also be an option for renters. The new solar package from the federal government in Germany has introduced some simplifications. According to Stiftung Warentest, the purchase costs for a system, depending on how much electricity is generated and consumed, are recouped after five to eight years. However, as “Stiftung Warentest” (issue 05/24) has now found, some of the balcony power plants are underperforming.
Eight Balcony Power Plants Tested at “Stiftung Warentest”
The testers examined eight balcony power plants, each consisting of two photovoltaic modules and an inverter, operating at a reduced capacity of 600 watts. In full sun, all tested systems generate plenty of electricity. However, if they are half in the dark, this is no longer the case. In this case, all systems in the test produce no electricity at all. Even the top-performing system delivered just over half of its capacity when a quarter of the system was covered.
Wasted Potential Due to Tilt Angle
Another point of criticism: On the balcony railing, the mounting of one of the tested systems forces the associated panels into a vertical position. This wastes potential and reduces electricity yield, according to the testers. After all, the panels capture the most light with a tilt of 30 to 40 degrees to the horizontal. The tilt angles allowed by the other system mounts in the test range from a maximum of 15 degrees to 35 degrees.
Note: If you’re wondering how much electricity and money can be saved with a plug-in solar device on the balcony, on the house wall, or on the roof, you can calculate it with the “Plug-in Solar Simulator” from the Berlin University of Applied Sciences.
Deficiencies in Stability
In terms of stability, the testers did not see only positives. While all tested systems proved to be waterproof and hail-proof, some panels can break if snow accumulates on them and it storms. For two test candidates, this occurred at a pressure load of 5,400 pascals (about 540 kilograms per square meter), while the PV panel of one provider broke at just 2,400 pascals (about 240 kilograms per square meter).
Problems with Inverters
Another critical point is the electromagnetic compatibility of the inverters sold with the systems. Inverters convert the generated direct current into alternating current, which household appliances use. They are necessary but can electromagnetically interfere with electronic devices and radio connections, potentially causing home internet to lag or even disrupting police and emergency services’ radio networks.
Particularly disruptive is an inverter sold with three of the balcony power plants in the test, and according to “Stiftung Warentest,” it has been temporarily removed from the market for review by the Federal Network Agency. However, this does not entail a right to exchange.
At least, Inverters are not permanently installed in the system. They can be replaced, albeit not without cost, according to the testers. They awarded a “poor” rating three times in the overall evaluation for the affected systems.
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Test Winner is the Cheapest Solar Module
Overall, only one balcony solar system received a “good” rating. It was the cheapest in the test: EPP Solar Balcony Power Plant 830W. However, according to the information, it is a discontinued model. Three balcony power plants received a “satisfactory” rating, and one was “sufficient.”
Solar Package Eases Registration of Balcony Power Plants
With the solar package, the federal government aims to increase the share of solar energy in Germany. This year, 13 gigawatts of solar capacity are expected to be added, and by 2025, even 18 gigawatts. As a result, the registration of balcony power plants has been simplified. It is no longer necessary to inform the grid operator; a simple entry in the Federal Network Agency’s market master data register suffices. Additionally, the maximum inverter capacity has been increased from 600 to 800 watts.
With material from dpa
The German original of this article was published in April 2024.