[icehawk]

> It's a whole different paradigm than your UPS under your desk is: With your UPS, your system(s) receive a signal that things are running on local battery, and you've elected to configure things to use that signal to order an automated shutdown.

The setup you described there wasn't the situation I was describing at all.

I was describing a situation where there is utility power, a UPS, and a standby generator. When the utility power goes out, the generator has to start, stabilize, and only then can the load be transferred off the battery.

The requirement is that the UPS meet this current power demand for longer than the generator start up and transfer time (the "holdover time" I was speaking about in the previous post.)

For things like frequency response the holdover time is a fixed requirement. ERCOT requires all energy storage resources be able to maintain output for 15 minutes.