Glossary
Primary control reserve (PRL)
Also known as: Primärregelleistung, PRL, Primärregelung, FCR, Frequency Containment Reserve, Primary control
Primärregelleistung (primary control reserve, PRL) is the first tier of control reserve in the Swiss electricity grid: it stabilises grid frequency automatically within 30 seconds of a disturbance, such as the outage of a power plant. Swissgrid held around 70 MW for this on annual average in 2025; from 2026 it is 80 MW (ElCom). The minimum bid is 1 MW; smaller systems take part through a pool. Battery storage systems suit this product because they change their output in both directions without start-up time.
Primary control reserve responds directly to grid frequency: if it drops below 50 Hz, the participating systems feed in more; if it rises, they cut back. The response is local, with no signal from Swissgrid, and the reserve is held symmetrically in both directions. After 30 seconds, secondary control reserve takes over (Swissgrid Balancing Roadmap).
For businesses, PRL is rarely the first step into the balancing energy market: the volume of around 70 MW is small, and holding the reserve requires a battery that stays permanently available in both directions. More often, storage systems combine secondary control reserve with peak shaving and self-consumption.
Which of the three tiers is an option for your system and what the market pays for it is explained in the article Balancing energy with battery storage. Market access runs through a pool.