How much power supply (PSU) wattage do you need?
The power supply feeds your whole build. Here's how to size wattage and pick a quality, safe unit.
The power supply (PSU) converts wall power for every component. Get the wattage and quality right and the rest of the build runs stably; cut corners and you risk instability or worse. It isn't the place to save a few dollars.
Sizing the wattage
Add up your components' draw — the GPU and CPU dominate — and leave headroom (roughly 30–40%) for spikes and efficiency. A modern single-GPU build is commonly fine on a quality 650–850 W unit; high-end cards or heavy overclocks want more.
- Entry / office build: about 450–550 W is typically plenty.
- Mainstream gaming build: about 650–750 W covers most mid-range cards with headroom.
- High-end / power-hungry GPU: about 850 W and up, with the right connectors.
Quality and connectors
Choose a reputable unit with an 80 PLUS efficiency rating and the connectors your GPU needs (newer high-end cards use a 12V-2x6 / 12VHPWR cable). Headroom also keeps the fan quieter and the unit cooler. BuildBox flags when a chosen PSU is undersized for the build.
What happens if my PSU is too small?
The system can crash under load, fail to boot, or in bad cases damage components. Always size with headroom; the builder warns when wattage is too low.
Is higher wattage always better?
Not exactly — you want enough wattage plus headroom, from a quality unit. Vastly oversizing wastes money without adding performance.
What does 80 PLUS mean?
It's an efficiency rating (Bronze, Gold, and so on) — higher tiers waste less power as heat and often signal better build quality.