Small photovoltaic systems for the balcony, roof and garden reduce energy costs permanently, only need to be registered once and can be put into operation without a specialist or any modifications to the house’s electrical system. The mini systems known as balcony power plants consist of one or more photovoltaic panels and an inverter, which is connected directly to the home power network. As soon as the sun shines and the panels produce electricity, a maximum of 600 watts (expected to be 800 watts from January 1, 2024) will be fed into the power grid.
As our individual tests of balcony power plants show, the definition of a complete set is interpreted quite differently by manufacturers and retailers. With one exception, all of the systems were so complete that they could be used straight away – at least in theory. However, individual components are often missing for long-term use and proper installation, which is why you should plan carefully before purchasing. We show the sets we have tested so far in our Top 6: The best balcony power plants.
Below we show useful accessories that are needed in practice.
Brackets
It starts with brackets for the solar panels, which are not included in all sets. The panels can be attached to the balcony railing, on the flat roof and meadow, on the wall and on the roof. In addition to flat mounting, angled mounting using a so-called stand is also possible. It ensures that the panels can be better aligned with the sun and thus achieve more yield.
At specialist retailers such as Priwatt and Yuma you can choose whether and which attachment you want. With the set from the discounter Netto (test report), however, there is no choice whatsoever. Here you have to take action yourself, which can sometimes be expensive. Although the prices for panel mounts have fallen noticeably in recent months, the mounts are still usually cheaper as a set. If you still buy individually, you have to pay attention to the appropriate panel size.
In most sets, the inverter is mounted behind the panels. But here too there are exceptions and appropriate accessories are not always included. If you want to hang the inverter somewhere else, you can often screw it directly to the wall, but the cable length is often no longer sufficient, which brings us to the next point.
Cables and extensions
As a rule, the sets can be plugged together directly, but the cables are often too short for safe and tidy assembly. It starts with the connection cable between the inverter and the power grid. This needs the appropriate plug (Schuko or Wieland) and must also be sufficiently long. It then disappears into a cable duct for inconspicuous installation.
However, problems with the cable lengths of the solar panels are much more common. For example, if the inverter is not attached directly in the middle between the two panels, the short connection cables are usually not sufficient. Suitable extension cables with MC4 connectors are available ready-made in different versions. Although removing the waterproof MC4 connectors requires sensitivity and force, in our experience it is worth investing in a special tool. This is often included as a plastic version with extension cables. The aluminum version is better and more stable and costs 6 to 7 euros.
In addition to different lengths, the cables are also available with different diameters. It is important that the pipes are not dimensioned across the board, but rather based on the planned system size. Although the thinner 4 mm cables can also be used for individual panels, if you want to be on the safe side, buy cables with a 6 mm cross section. Nothing more is necessary with a balcony power plant. Since the range of cables is huge, you should definitely pay attention to the prices. The differences are sometimes immense and expensive is not necessarily better.
Basically, the cables should be sufficient, but not unnecessarily long. If cables are laid over longer distances, they should always be protected against fraying. This works with a cable protection tube, cable duct or cable pipe. The bare cables should never be left on the ground – even when installing in the garden or on a flat roof. Despite the rubberized coating, they should not be left in damp or wet conditions!
If you want to determine your own cable lengths, you can also assemble the MC4 extension yourself. Crimping pliers, connectors, contacts and cables are also available individually. If you have no experience in this area, it is better to use the ready-made cables. Incorrectly crimped cables pose a safety risk!
Revenue recognition
Many microinverters offer the option of querying performance data via WLAN and app. If you don’t want that, you can use models without any data connection.
Multiple adapters
It continues with adapters, which are also often needed. In the Ecoflow test set, we got very light and flexible 100-watt panels instead of the usual rigid 400-watt panels. Advantage of this variant: You can easily mount it higher than 4 meters above the ground. Disadvantage of this solution: The MC4 cables from the panels have to be combined to connect to the inverter, but a suitable adapter was not included in the scope of delivery.
The MC4 adapters and branch connectors for connecting panels in parallel are available with two, three and four connections starting at around 10 euros. Cable adapters are a little more flexible than the rigid plastic version, but less compact. The adapters should also be secured properly and not left on the floor, which can be done with cable ties.
When using adapters, you should know what you are doing. Large panels cannot simply be connected together at will! Basically, you always have to keep an eye on the performance data of the individual components.
Protective caps
Unfortunately, protective caps for unused connections on the inverter are almost always missing. Protective caps are available for the MC4 connections and for the connecting cable to other inverters. If you do not hang up the inverter in a protected manner, you should secure the connections properly. We recommend doing this in a protected environment to protect the expensive electronics from moisture and dust.
Window feedthrough
If you want to hang the inverter indoors, for example to use it with a storage device, you have to get the solar cables into the interior. There are wall and roof feedthroughs, for example, but the cable must be crimped to use them.
It is easier to use a window feedthrough, such as those used for satellite TV cables. We use this solution with the Ecoflow Powerstream storage solution. Depending on the manufacturer, a pair of window bushings costs between 16 euros and 27 euros. However, such a solution should be used on windows that are not constantly opened, otherwise the flat cables could be damaged in the long term.
Electricity storage
The main problem with balcony power plants is that the electricity produced has to be consumed directly. Service that is not requested ends up with the network operator free of charge. Since many heavy consumers such as washing machines and kitchen appliances are only used in the evening, you are wasting money here.
One solution is storage, with which excess electricity can be fed into your own home network at night and as needed. However, feeding directly into the public network from the storage facility is not permitted and would also be unprofitable. Although balcony power plants can theoretically be registered for a feed-in tariff, this involves higher costs and is therefore usually not worth it.
cooling
Unfortunately, solar systems do not achieve their highest efficiency at high temperatures – quite the opposite. Inverters placed directly in the sun can quickly overheat. This usually leads to a shutdown, as a result of which electricity no longer flows into the house network. The outages usually only last for a short time, but performance is still lost. During the test, the Ecoflow inverter was sometimes unavailable for an entire afternoon at very high temperatures. Other models were less sensitive in the tests, but precautions should generally be taken here. Ideally, the inverter should hang in the shade!
If this is not possible or the temperature still rises too high, small electric fans help to keep the temperature under control. Small solar fans that also get their power from a small photovoltaic panel are practical. Such fan panel sets are available from around 20 euros. With two fans it starts at around 25 euros.
A protective box around the inverter sounds good, but without appropriate ventilation heat builds up very quickly.
Conclusion
Anyone planning their balcony power plant should also think about the fastening and the exact location of the cables in order to avoid surprises during commissioning. If you buy your set from a specialist retailer, you will often get significantly more accessories than from a discounter.
For a safe and visually appealing installation, the cables used must be sufficiently long and protected against fraying. If you have no experience crimping contacts, you should use ready-made cables and extensions for safety reasons.