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The commune of Auenstein (AG) has decided to replace its conventional water meters with radio water meters. These enable the water engineer to read the water level of the individual residential units as they pass by (walk-by, drive-by). This eliminates the need for manual reading in each house. The community’s consideration is in the interest of efficiency. Resident A. of the community is not happy about this. According to his research, the radio water meter used allows a radio transmission of the measured water data every 30 seconds. He tries to appeal his concerns before the cantonal authorities, but is unsuccessful. Because of this failure, he brought his objections before the Federal Supreme Court.

The Federal Supreme Court had to decide whether the new meters violate the constitutionally protected right to informational self-determination.

The newly installed meters measure water consumption and store the hourly rates on an internal data logger for 252 days. According to the Federal Supreme Court, this is personal data, as it allows drawing conclusions about residents with a water meter per unit. The court states further that there is also data processing taking place as the consumption rate is transferred to a mobile device once a year. For these reasons, the Supreme Court stated a violation of the informational self-determination

However, a restriction of this right can be justified under certain circumstances. The justification requires a legal basis and a public interest or the protection of fundamental rights of third parties. In addition, the interference must be proportionate.

The Federal Supreme Court found that there is a legal basis for the processing of data for the collection of water consumption at the relevant time for billing. The critical issue is that the water meter stores the data for 252 days and transmits it by radio every 30 seconds. Due to this storage, it is possible to use that data of the last 252 days at any time. Even if the commune only needs them once a year for the invoicing, there is still the possibility to read them at any time. According to the Supreme Court, there is only a legal basis for the billing, but not for the storage of water consumption data.

The public interest behind the new water meters consists in the more efficient determination of water consumption by the commune. In principle, there is no public interest in storing data on water consumption, since the commune never intended to use it in the first place.

Furthermore, the principle of proportionality has to be applied. This requires that a measure is suitable and necessary to achieve the public or private interest and that it appears reasonable for those affected in view of the severity of the restriction of fundamental rights.

With regard to suitability, the Federal Supreme Court holds that the selected method is suitable to read the water consumption. The necessity for this exists insofar as it is necessary for the invoicing. However, this is not the case for the storage of water consumption data for 252 days and for the radio transmission, which takes place every 30 seconds. For this reason, the method selected by the community of Auenstein (AG) fails in terms of proportionality. Consequently, no justification is possible and the use of these devices is unlawful.

In conclusion, this means that the data storage carried out violates the constitutionally protected informational self-determination. The lower court’s ruling must be overturned. The community must now examine whether other possibilities for measuring water consumption are available and at the same time comply with the residents’ data protection rights.