The power supply is the one component that can damage everything else. An under-sized or low-quality unit under load can cause random shutdowns, corruption, and in the worst cases take a GPU or motherboard with it. It is also the component people choose last and budget first — backwards.
How to estimate wattage
Add the CPU and GPU peak power draw, then add roughly 100W for the rest of the system (board, RAM, drives, fans). That’s your load estimate. Add 20–30% headroom so the PSU runs at a comfortable efficiency and handles transient GPU spikes. Converters like PC Part Picker show estimated wattage for an entire list — a useful cross-check.
| Typical setup | Estimated wattage | Safe PSU choice |
|---|---|---|
| 1080p mid system (e.g. RTX 4060-class) | 300–350W | 550–650W |
| 1440p high-end (e.g. 4070-class) | 400–450W | 650–750W |
| 4K flagship GPU | 550W+ | 850W |
| Multi-GPU / heavy AI compute | 700W+ | 1000W+ |
What 80 PLUS ratings actually mean
80 PLUS — Bronze, Silver, Gold, Platinum, Titanium — describes efficiency at given loads, not quality. A good Bronze unit is safer than a cheap Gold unit from an unknown brand. Treat the rating as a guide, and treat brand reputation and model reviews as the real filter. A genuine rating corresponds to third-party verdicts; popular, well-reviewed models from established brands are the safest picks.
Modular cables and connectors
Modular supplies let you attach only the cables you need — better airflow and much easier builds. Check connectors match your parts: modern GPUs use 12VHPWR/12V-2x6 or two 8-pin PCIe, and your PSU should ship the right ones. If a GPU needs 3 x 8-pin and your unit provides one, that’s a mismatch.
Bottom line
- Estimate load, add 20–30% headroom, then pick the PSU.
- Trust brand and model reviews over the sticker rating.
- Match connectors to your GPU and board (ATX 3.x for modern GPUs).
- Buy new for new builds — PSUs age and capacitors degrade.