The Federal Network Agency has called for caution when buying so-called energy-saving devices online.

When examining various types of such devices, numerous formal defects such as incorrect CE markings, missing German operating instructions and a lack of contact persons were found, the authority announced on Thursday in Bonn.

Countless energy-saving devices are offered online that do not meet the legal requirements.

The use of such devices is not permitted.

"According to the state of the art, the energy saving effects of such devices are questionable," said the head of the authority, Klaus Müller, according to the announcement.

According to the network agency, the tested energy-saving boxes should stabilize the flow of electricity in the household and thus lead to a lower electricity bill.

It would be enough to plug such a device into the socket.

With the devices, however, it was found that the components were often unprofessionally connected and soldered connections were missing.

The products are advertised with terms such as “energy or electricity saving box”, “electro saving box” or “energy saving device”.

These are not to be confused with energy-saving lamps, energy-saving thermostats or similar products that actually enable energy savings.

In the online market surveillance, the network agency has already identified 353 offers of non-compliant energy saving boxes on various online platforms this year.

At the authority's notice, more than a million products were removed from the respective platform operator.

The authorities had purchased the examined devices online outside of the EU.