The reason is the still more frequent cases of strained conditions on the German transmission grids caused by the "Energiewende".

The transmission system operators must every month invite the large industrial customers to tender on this special service. The tender should include 1,500 MW to be available within seconds and another 1,500 MW to be available within 15 minutes. The consumers will receive € 1,667 per MW ready for disconnection plus between 100 € and 500 € per MWh actually disconnected depending on the bids.

The average household is estimated to have an additional cost between 1 and 2 € per year. In return the household consumers will enjoy the better grid stability.

The presentation of the order on the web site of the Federal Ministry of Economics and Technology (BMWI) is discreet. A brief note in German is available here. Maybe the ministry is not exactly proud of this element of the "Energiewende".

For many years electricity consumers saw uninterrupted supply of electricity as a reasonable service in a modern society. The transition into uncontrollable electricity sources, such as wind power, will challenge this understanding. In several cases it will be cheaper to disconnect certain loads than to reinforce the electricity supply infrastructure.

The interruption of a few industrial customers is just the beginning. The more flexible electricity demand of the future will not only be moved a few hours in time, but also substituted with other energy carriers. Otherwise the necessary flexibility cannot be achieved.

The heavily loaded grids of the future will frequently be operated close to the stability limits. It will be a dilemma that larger safety margins mean more interruptions.