You definitely want to overbudget when you're looking at PSU ratings, especially for 24/7 mining. Running a PSU 24/7 close to its maximum is asking for trouble.

In general, you don't want to exceed about 70-80% of the PSU's rated capabilities. Buying a PSU capable of delivering more power does not cause you to use more power, but do note that most PSUs reach optimal efficiency if they're loaded somewhere around 50% of the rating. (For a better 80+ PSUs, this becomes less noticeable.)

Add up the TDP of the CPU and all of your graphics cards, under the assumption that you don't have an unusually high number of drives or fans. Then multiply the sum by 1.25-1.4 (subjective), and you have a rough estimate of what you're looking for (generally round up to the nearest typical PSU rating, but you could round down if the difference is small enough). You can usually get by with less, especially if you mess with clock & power settings, but that's for you to play around with.


Also check for the number of connectors, particularly PCIe 6-pin or 8-pin connectors. These are necessary for powerful cards in a multi-GPU system.

Look for PSUs with the guts manufactured by Seasonic, SuperFlower, FSP, Delta, or another reputable manufacturer. Most upper-end units from brands such as EVGA are made by one of these.

Those made by HEC, CWT, Sirfa/Sirtec are lower on the totem pole, but *usually* do okay. CWT especially has gotten better since they partnered with Corsair a few years back. However, for heavy 24/7 loads, I usually look for the OEMs in the above tier.

Those made by unknown OEMs should generally be avoided. Perhaps they'll be okay, or they'll fail. Worst case involves a crappy PSU damaging your other components.