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Comment by strivingtobe | Hacker News Reader

No. The 130 MW remaining capacity was the amount available "in SCED within 5 minutes", which in super simplified terms means "the amount of energy available quickly and economically".

The grid actually had ~4 GW spare capacity (according to the graph) if it was needed, but it wasn't part of SCED.

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But if you can't get more in under 5m, then if the demand goes up that much in under 5m you hit the point of load shedding to protect the grid right?

The graph showed it increasing fast just before. Is it so unthinkable it could jump again?

Or is that they could get more (non-SCED) in time, it would just cost a ton so it's avoided if at all possible?

My understanding is that it's the latter. "in SCED" basically means they have pre-planned availability that is cheap.

The "Physical Response Capacity" in that graph is the amount of capacity actually available, but it's not part of SCED. However it doesn't say anything about the timeframe it would be available in. Given that ERCOT didn't call for conservation, I would have to assume it was capacity that was "quickly available, but not cheap" rather than "not quickly available", but I don't know for sure.

Being in SCED just means that the resource bid into the real time energy market (which clears every 5 mins), it does not necessarily mean that the resource is cheap to dispatch. The confusion here might be caused by the differences of the ancillary market (PRC) and the energy market (SCED).

Your second paragraph may be answered by this: https://www.ercot.com/gridmktinfo/dashboards/gridconditions. PRC units are available in real time, immediately on request.

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