Yep, we have battery-backed generators for UPS and a transfer switch at the 480-V feed that comes into the room but it is not enough to power the compute nodes.

Yep, we have battery-backed generators for UPS and a transfer switch at the 480-V feed that comes into the room but it is not enough to power the compute nodes. The UPS allows cluster management nodes and the parallel filesystem (which is a small cluster by itself) to ride through full outages and other PQE.