That will be plenty, Id think. An R710 will sit at around with no load  200w, 0.6amp/ so that will be around 20mins+/- runtime, are you adding switches and other hardware to the UPS as well? The software will allow you to choose from max run time and power off at 5min power left,,or max power-saving and put the server into a low power state as soon as an outage is detected after a set time. the one i have is the CyberPower VALUE2200EILCD Value Series (1320W/2200VA) that runs my pc for a good 45mins on battery at 190w
Trying to determine what type of UPS to buy that will have enough wattage to handle my R710's. Servers: R710 750w x 2R710 550w x 2 My plan is to buy two of these:CyberPower CP1500AVRLCD Intelligent LCD UPS System, 1500VA/900W, 12 Outlets, AVR, Mini-Tower  For the 750w rig, connect one power supply to the first battery backup outlet and one to a non battery backup outlet on the first UPSFor the 550w rig, connect one power supply to the second battery backup outlet and one to a non battery backup outlet on the second UPS Does that sound like an acceptable solution or is that not wise?  I don't need both power supply's on backup but I would like to have one and just have them gracefully shutdown if we have an outage that lasts 1 or 2 minutes.
UPS Backup for R710's (750w and 550w)?