I'm putting together a system with a Ryzen 7 9800X3D, an RX 9070 XT Pure, and an 850W Gold-rated Cooler Master power supply. I'm choosing between a 1500VA UPS rated around 900W and a 2000VA model. Most of my research suggests the 1500VA unit should be sufficient, but I've also seen advice recommending 2000VA to prevent shutdowns during transient power spikes. I may undervolt the GPU to around 270W, and I'm not planning a major upgrade for the next five years. Has anyone run a similar setup, and would the extra 500VA make a meaningful difference?
3 Answers
A 1500VA unit rated for 900W should also handle one or two monitors, as long as you stay within its wattage limit. VA by itself isn’t the whole story; the UPS’s actual watt rating matters more. Keep nonessential devices on the surge-only outlets and reserve the battery-backed outlets for the PC and the minimum number of monitors.
I ran a 12900K and 3080 Ti from a 1500VA/900W UPS for years without trouble. After moving to a much more power-hungry graphics card, I switched to a 1500VA model rated at 1000W. If a UPS is shutting down because it can’t supply enough watts, moving from 1500VA to 2000VA won’t necessarily fix it unless the higher-capacity model also has a higher watt rating. Also check the battery’s age—old batteries can cause random shutdowns even with a very small load.
A 1500VA/900W UPS should be plenty for this system. The CPU and GPU together are roughly 440–470W at peak, and adding memory, storage, fans, and PSU losses should still leave the total wall draw under about 600–700W. The PSU’s input capacitors also help smooth brief power transients. If you connect the UPS to the computer by USB, its load meter can confirm the actual usage.
Thanks for the explanation—that’s reassuring.
That makes sense. I’ll go with a 1500VA/900W model and won’t connect anything unnecessary to the battery-backed outlets.