Plug-in solar devices: With standards and seals

Generating solar power at home is easy. A plug-in solar set can be had for just a few hundred euros from a supermarket or DIY store. Some systems take less than an hour to set up: find a sunny spot, position the module on its assembly system, clip some connections together and plug it in – done! With energy prices high and a VAT exemption in place for photovoltaic products, mini PV systems have recently been flying off the shelves faster than ever. The exact figures are hard to get a handle on, however. The latest data from the market master data register at Germany’s Federal Network Agency indicates that the country has almost 400,000 PV systems with up to four modules, the majority of which are likely to be plug-in solar devices. But although registration is a legal requirement (with fines for non-compliance), many owners of plug-in solar equipment continue to generate their power in “guerrilla” mode. Christian Ofenheusle from EmpowerSource, which has been following the technology’s development for years, estimates that there were actually around 1.5 million devices connected to the grid in Germany in summer 2023 – a figure he bases on conversations with leading providers.

First standard for feeding into final circuits

Given the sheer number of the devices, plug-in solar generators can now be considered commonplace. That said, the familiarity of such products is no guarantee that they are safe. Using DIY methods, technical amateurs can use plug-in solar power systems to feed power into final circuits that were not designed for this purpose and lack corresponding protection. The DIN VDE V 0100-551-1 (VDE V 0100-551-1) installation standard for low-voltage installations was therefore revised in 2016 to cover the safety aspects of feeding power into household sockets. The plug connections were a crucial point. The low-voltage standard requires them to protect users so that they do not sustain an electric shock from the contact pins. Along with a fixed connection, the standard requires a special energy socket for this purpose. The mains and system protection in the inverter, which prevents the feed-in of electricity if there is no frequency signal from the grid, does not in itself provide sufficient protection from electrocution.

A second update from 2016 also enabled amateur electricians to register plug-in systems rated at up to 600 watts with their grid operator. For mini PV systems, the revision of the standard marked a milestone. It was the first time there had been any such standards governing grid feed-in. However, since the norm has no legal force and there are few ways (particularly in single-family homes) to prevent people from plugging their devices into standard sockets, many solar plug-in operators have ignored this part of the rules.

The quest to establish a practical seal

It’s a situation that's obviously less than ideal, and one VDE has been attempting to address – including in a position paper in early 2023 that called for simplifications to various standards. These would include a safe solution for enabling connections to standard sockets. So far, what plug-in solar power systems look like and whether they come with instructions and safety advice has been largely left up to the manufacturers.

Customers have often put assembly systems, inverters and modules together themselves to their best ability – not realizing that this has put them on thin ice regarding issues of liability. Serious plug-in solar providers, solar energy organizations and standardization specialists from VDE have therefore long agreed that a product standard is needed alongside the low-voltage standard. Getting such a standard on the table, however, has been a long process.

The consortium members of the SteckerSolar project, which is being funded by the German Federal Ministry for Economic Affairs and Climate Action, discussed the details of the future product standard from August 2020 to July 2023. The participants included the DKE, the German Solar Energy Society (DGS) and the plug-in solar providers Indielux and Solarinvert. The publication of the standard with binding statements on the 600 or 800 VA power limit and the much-discussed plug issue was expected at the beginning of January.

Another key aspect of the product standard will cover how the devices are physically secured, which is currently left to the user for the most part. Providers will now have to include installation instructions and prove that their assembly method is structurally suitable.

They will be able to request certification from a recognized testing institute such as VDE to show that their plug-in solar device meets the new standard. Thanks to the certificate, consumers will be able to recognize right away whether a device is safe. “People who use a standardized device and follow the instructions will be able to prove to an insurance company that they have not been negligent,” says Arnd Roth, pointing out an advantage for consumers in the event of any damage caused by their solar installations. Roth is a technical manager at VDE Renewables, where his responsibilities include testing plug-in solar power systems.

The importance of a suitable location

VDE has already been offering certification for plug-in solar devices since September based – for now – on the draft standard from October 2022. As soon as the final version is available, certification under the new rules will begin. Plug-in solar is being advertised with sometimes impressively short payback periods. The comparison platform Verivox, for example, cites four to six years under “ideal conditions.” This assumes that a 600-watt system can produce an annual yield of 570 kWh. On top of a sunny carport in southern Germany, for example, that figure is certainly achievable. Buy a low-cost solar set and consume most of the power yourself, and your installation will quickly pay for itself.