Operating reserve

In electricity networks, the operating reserve is the generating capacity available to the system operator within a short interval of time to meet demand in case a generator goes down or there is another disruption to the supply.

Most power systems are designed so that, under normal conditions, the operating reserve is always at least the capacity of the largest supplier plus a fraction of the peak load.

[3] This is because the spinning reserve is slightly more reliable (it doesn't suffer from start-up issues) and can respond immediately whereas with non-spinning reserve generators there is a delay as the generator starts-up offline.

[5] Centrally controlled air conditioners and thermostats that are used in large residential areas can be used as a fast and considerable curtailment reserve.

[6] Operating reserve is a crucial concept for ensuring that the day-ahead planning of generators' schedule can withstand the uncertainty due to unforeseen variations in the load profile or equipment (generators, transformers, transmission links) faults.