Ancillary services (AS) in the electricity supply sector are defined as services delivered by grid operators to customers in addition to the transmission and distribution of electrical energy. This includes the provision and operation of a schedule and congestion management system as well as coordination activities in Switzerland and Europe. By far the greatest share of costs for ancillary services, however, is taken up by control energy. This is a kind of insurance against power outages that Swissgrid takes out with electricity producers and consumers in order to cope with critical grid situations if unforeseen events occur.

This «insurance» is needed because electricity cannot be cost-efficiently stored in large volumes using conventional means. At any given point in time, therefore, the amount of electricity produced must correspond exactly to the amount being used. If this balance is endangered, for instance in the case of failure of a power station or a major consumer, the missing or excess energy must be compensated for immediately using control energy. In such a scenario Swissgrid contacts the ancillary service providers with which it concluded an agreement in advance. These then perform their agreed service, i.e. either increasing or decreasing their energy production. At present, ancillary services are mainly offered by producers such as pumped storage power plants. On the condition that the minimum requirements defined by Swissgrid are met, electricity consumers that can flexibly ramp up or reduce their electricity consumption can now also offer control energy services.

Swissgrid is obliged by law to procure ancillary services in accordance with transparent, non-discriminatory and market-oriented criteria. As the company does not possess any power plants of its own, it invites tenders on the control power market newly created in 2009 and then chooses the most favourable. Since 2009, Swissgrid has successfully implemented a series of measures to drastically reduce the cost of procuring ancillary services. In addition to introducing an upper price limit and developing new, more flexible products, particular emphasis is placed on expanding the range of offerings. As a result, Swissgrid is the first company in the whole of Europe to buy control energy internationally. The fact that prices nevertheless rose for end consumers at the start of 2011 is due to a ruling by the Federal Administrative Court of July 2010. Until now, part of the cost of ancillary services has been carried by power plants with an output of more than 50 megawatts. The ruling by the Federal Administrative Court declared this to be illegal. As a consequence, since the beginning of 2011 the entire costs of procuring ancillary services have had to be charged to end consumers. Despite this ruling, the various cost-cutting measures have enabled Swissgrid to reduce the ancillary service tariffs für 2012 by 40%.