Speaking from a Cisco perspective; this is not the case. The typical AC power supply in Cisco kit is around 93% efficient. The DC power supply option (which you can purchased for direct connection) is around 70% to 80% efficient. So those people who elect to use DC only for power will need a lot more power. The reason for this is it is more efficient to convert 240VAC (or 110VAC) to 12VDC, 5VDC (and sometimes 3.3VDC and 48VDC), than it is to convert 12/48VDC to those same voltages. Most military network equipment is not DC powered. If you have a tight power budget you need to go AC. -----Original Message----- ... UPS and Battery Backup are a joke, I often wonder why critical systems don't employ external direct connections to battery systems rather than having to used PSU's, UPS's and Inverters. Granted these are often packaged in pretty housings but they are still not as efficient as running a device off the power it was designed to work with. Take a leaf out of the Military's book. Most of their gear has an external DC option so it can be connected to something in the field and will run for ages. ...