PC PSU Calculator

How to Choose the Right PSU Wattage

The 80% rule is the foundation of PSU sizing: a power supply runs most efficiently when operating between 50% and 80% of its rated capacity. If your system draws 400W at peak, a 550W PSU operates at 73% load — ideal. A 1000W PSU at 400W load runs at only 40%, below the efficiency sweet spot, meaning you paid more for a unit that wastes more energy as heat. The rule of thumb: calculate your total system draw, multiply by 1.25 (25% headroom), then round up to the next standard PSU size (450 / 550 / 650 / 750 / 850 / 1000 / 1200W). The headroom is critical for GPU transient power spikes and leaves room for future upgrades. Never size a PSU at exactly your calculated load — peaks will exceed your sustained draw.

PSU Wattage by GPU Generation (2026)

Your GPU TDP is the single biggest variable in PSU sizing. The NVIDIA RTX 5090 has a 575W TDP — the highest consumer GPU ever released — requiring a 1000W to 1200W PSU for a full build. The RTX 4090 (450W TDP) pairs well with 850W to 1000W. Mid-range cards like the RTX 4070 (200W) work with a 650W PSU for most builds. Budget gaming builds using an RTX 4060 (115W) or RX 7600 (165W) are well served by a quality 550W unit. Always check NVIDIA's and AMD's recommended PSU wattage on the GPU product page — these are stated minimums for the card alone, not the full system. Add your CPU TDP on top, then apply the 25% headroom multiplier. For RTX 5090 builds with a high-TDP CPU like the i9-14900K, a 1200W to 1600W PSU is not overkill. Last updated: March 2026 with RTX 50 series and Ryzen 9000 data.

80 Plus Certification — Bronze, Gold, Platinum Explained

80 Plus certification measures how efficiently a PSU converts AC wall power to DC power for your components. Bronze achieves 82% efficiency at 50% load, Gold achieves 87%, Platinum achieves 90%, and Titanium achieves 92%. The real-world electricity cost difference between Bronze and Gold for a 650W PSU running 8 hours a day is roughly $10 to $15 per year. For casual gaming, 80 Plus Gold is the recommended minimum — balancing cost and efficiency. Platinum makes sense for high-wattage builds (850W and above) and always-on workstations where the savings add up over time. Titanium is typically reserved for server and workstation environments. Critically, cheap unrated PSUs often overstate their wattage, run hot at sustained loads, and can cause system crashes or component damage. Always buy from a reputable brand: Seasonic, Corsair, be quiet!, or Super Flower OEM units. A quality PSU is not where to cut corners in a build.

Common PSU Sizing Mistakes to Avoid

The most dangerous mistake is undersizing. A PSU running at 90-100% of its rated capacity generates excess heat, degrades capacitors faster, and can cause system instability or immediate shutdown during GPU power spikes. Modern GPUs like the RTX 4090 and RTX 5090 can spike well beyond their sustained TDP for milliseconds during heavy load — this is why PCIe 5.0 power connectors were introduced to handle transient delivery more cleanly. The second mistake is over-sizing without reason: a 1200W PSU for a 300W system wastes electricity and costs more. The third common mistake is ignoring GPU OC potential — if you plan to overclock your GPU, add 50W to your GPU draw estimate before calculating. Finally, never buy an unbranded or deeply discounted PSU from an unknown manufacturer. A failed PSU can damage your CPU, GPU, RAM, and motherboard simultaneously. Budget an extra $20 to $40 for a known brand with a 5 to 10 year warranty — it is the cheapest insurance you can buy for your entire build.