The system shouldn't draw more than 800W at peak and the PSU is 92% efficient; therefore it would draw 870W from the outlet. If you connect a 40W monitor, then the total load would not exceed 910W. Unless you are running benchmarks, the system will draw less than 900W. A 900 Watts UPS like the CyberPower CP1500PFCLCD should be enough, but a 980 Watts TRIPP LITE SMART1500XL 1500, a 1000 Watts CyberPower PR1500LCDRT2U or other quality 1000 Watts UPS would be better, but they cost a lot more.