Choosing a Power Supply (PSU): Wattage, Efficiency and Protection
The power supply is what protects everything else
A lot of people economise on the power supply — and that is a mistake. A weak or cheap unit can fail and take other components with it. A good one gives you stability, protection, and a longer life for the whole system.
1. Work out the wattage you need
Add up the draw of your CPU and graphics card (the two that matter most) and add a 20-30% safety margin. Rough guidance:
- Mid-range 1080p system: 550-650W.
- 1440p system with a strong card: 750-850W.
- 4K system with a flagship card: 1000W and above.
2. 80 PLUS efficiency ratings
The rating tells you how efficiently the unit converts power — less waste heat and a lower electricity bill:
- 80 PLUS Bronze: a solid starting point for budget systems.
- Gold: the best balance of price and efficiency — what we recommend most often.
- Platinum / Titanium: the highest efficiency, for powerful systems and workstations.
3. Modular or not?
- Fully modular: connect only the cables you need — tidier build, better airflow.
- Semi / non-modular: cheaper, but more cable bulk inside the case.
4. ATX 3.0 and PCIe 5.0 support
If you are fitting a current graphics card, look for a unit that supports ATX 3.0 / 3.1 with a 12V-2x6 (PCIe 5.0) cable, so you avoid adapters and get stable power delivery under load.
5. Protections
Check the unit carries OVP/UVP/OCP/OPP/SCP protection (over- and under-voltage, over-current, over-power, and short circuit). These are what shield your components when something goes wrong on the mains.
Save with Open Box
We carry fully modular units from trusted brands like Corsair, ASUS ROG, Cooler Master and be quiet! — all Open Box, tested, warrantied, and 30-50% below new. Browse Open Box power supplies.