generation capacity that is online but unloaded and that can respond within 10 minutes to compensate for generation or transmission outages. “Frequency-responsive” spinning reserve responds within 10 seconds to maintain system frequency. Spinning reserves are the first type of reserves used when shortfalls occur.
Pros
Provides grid operators options to compensate for sudden and unexpected loss of another generation source.
Cons
Not a contract guaranteed revenue.
Real Talk
The name spinning reserve comes from the use of large rotating (spinning) mechanical energy generators (e.g. steam turbines).