Another important consideration is the PSU 'form factor.' The most common form factor is ATX, compatible with most mid-to-full-sized PC cases. For smaller PCs, you might want SFX or TFX form factors.

Digital Trends A bite-sized PSU buying guide is that you need to look at the wattage, the efficiency rating, the form factor (and thus, the size), and lastly, the connectors when you buy a PSU.

Form Factor: Depending on the form factor of the PC, a PSU can be ATX (fits all ATX PC cases), TFX (for mini or home-media PC), SFX (works with mini-ITX or even micro-ATX.), or SFX-L (micro-ATX ...

So we see what differences they offer and why you might consider them. Best power supply for gaming PC Corsair RM850x Seasonic PRIME TX-1000 Thermaltake Toughpower GX2 600W ...

Priced around $150, the PSU is also ATX 3.1 PCIe 5.1 compliant meaning that it comes with the new 16-pin (12V-2×6) PCIe connector and bundled cable that can deliver up to 600W of power.

If you’ve spent enough on the rest of your build, the power supply might be your last thought so you might just want the best budget PSU instead. So there the EVGA 750 GQ is the choice for you.