Generate electricity yourself: COMPUTER BILD has tried it!

The dream of self-generated electricity has so far only come true in Germany – if at all – for a few homeowners with a suitable roof area. In a rented apartment, however, the chances are zero. Unless you have a balcony or a small garden shed with electricity. With “balcony power plants” you generate your own solar power without much effort. COMPUTER BILD shows how you can generate electricity yourself.

Simple balcony power plants with a single solar module are available for a few hundred euros. At the Bavarian online retailer Alpha Solar, for example, customers get a 365-watt solar module from the quality manufacturer JA Solar, all the wiring and a so-called inverter. The small device is the brain of the system, converting the electricity produced into alternating current and making it ready for the 230 volt voltage in the home. Depending on what is needed, the customer also orders a set-up trapeze for the garden or metal rails for roof or balcony installation. Once assembled, the owner of the house simply connects the solar power plant to the normal household electricity network. Sounds very physical, but is not a problem. And that’s also the highlight: The electricity produced is not stored in a battery or fed into the general grid for a fee, as is the case with large systems, but is used directly in the home.

Such an entry-level power plant in the maximum configuration with two solar modules should produce around 400 kilowatt hours per year. That would be almost 10 percent of what a four-person household consumes in a year. In order for the technology to achieve such values, the location should be right. In addition, prospective electricity producers are not allowed to grab the first solar cell that comes along. “Rather spend a few euros more“, advises Alexander Wohldorf from Alpha Solar. “After all, the solar cell should still provide as much power as possible even after many years.“So some manufacturers also give a 25-year performance guarantee. Depending on the electricity price and yield, the buyer has already recouped the costs for the system after ten to twelve years thanks to the savings in electricity costs. The environment also benefits: Compared to conventional electricity generation, one saves 600 watt solar system around 5 tons of carbon dioxide in 20 years.

But how big does the system have to be? Is a single solar panel enough – and if so, with how much power? For plug-in solar devices that only generate electricity for self-consumption, the amount of electricity produced should be below the base consumption. Even when you’re away, the fridge or router always provide a certain basic requirement. Here is a rule of thumb for the output size of solar systems for self-consumption:

• 1 to 2 people: 250 to 400 watts
• 3 to 4 people: 500 to 900 watts

Too bad for large families: In Germany, the simple solar systems for the socket are only designed for an output of up to 600 watts. Nevertheless, there is a way to get the most out of the plug-in solar system: you simply install modules with a slightly higher total output, around three modules of 300 watts each. First of all, the system rarely achieves peak performance. Second, the inverter limits the amount of electricity it sends to the outlet. Example: If the solar modules generate 750 kWh on a sunny day, the inverter cuts off the electricity feed-in at 600 kWh. The advantage: a minimally oversized system pays off on shady days.

South-east facing, at a 36-degree angle and without shade – this is how the modules of the plug-in solar power plant capture the most solar energy. But even if the positioning is not quite perfect, a solid yield is possible. In order to align the modules as well as possible, the following options are available:

• On the balcony: Attachment to the outer grille is common here.
• On the roof: A roofer attaches the modules to the tiles with special hooks.
• On open spaces: There are already prepared solar modules with stands for the garden.

The assembly and commissioning of such a power plant is very easy and can be done without an electrician or solar specialist. The buyer only needs to connect a few plugs. When connecting to the socket, however, the question of conscience arises: “Plug & Play” power plants usually have the supplied Schuko plug. It can simply be plugged into the socket – and off you go. Sticking point: This procedure does not correspond to the specifications of the VDE (Vbound i.ehe Eelectrical engineering). He recommends a so-called Wieland socket for the connection. It looks a little different than a conventional socket, but it also fits easily into the wall if you replace it.

It is intended to provide more security and is a manageable investment at an additional cost of 50 euros. On the quiet, however, many experts consider this to be exaggerated. According to estimates, around 220,000 solar power plants with ordinary plugs are running in Germany. “In any case, the inverters have to be built in such a way that they switch off in a fraction of a second in the event of problems“, according to expert Wohldorf.

If, contrary to the recommendations, you actually plug the solar device into a normal socket, you can connect a smart socket with a built-in electricity meter there. The FritzDECT 210, for example, transmits the data to the FritzBox. Alternatively, there are measuring modules for inverters, for example from Envertech – the “Envertech Bridge” (around 90 euros) provides information via WLAN.