ganak.appPSU Calculator
Calculate the right PSU wattage for your PC build. Enter CPU and GPU power draw, storage, fans, and cooling to get recommended power supply size, per-component breakdown, efficiency tier comparison, and annual electricity cost estimates. Vendor-neutral, no product bias.
Power Breakdown
Per-component power draw
Load Profiles
Estimated power at different usage levels
Efficiency Comparison
Annual electricity cost by PSU efficiency tier
| Tier | Eff. | Wall W | $/Year | Savings |
|---|---|---|---|---|
| 80 Plus | 80% | 505 | $176.95 | — |
| 80+ Bronze | 85% | 475 | $166.54 | — |
| 80+ Silver | 88% | 459 | $160.87 | $5.68 |
| 80+ GoldBest Value | 90% | 449 | $157.29 | $9.25 |
| 80+ Platinum | 92% | 439 | $153.87 | $12.67 |
| 80+ Titanium | 94% | 430 | $150.60 | $15.95 |
* Savings compared to 80+ Bronze. Based on typical 50% load. Actual costs vary by usage patterns.
Connector Requirements
Cables your PSU must provide
- 1x 24-pin ATX (motherboard)
- 1x 8-pin EPS (CPU)
- 2x 8-pin PCIe (GPU)
How to Calculate PSU Wattage
Understanding power supply sizing for your PC
Your PSU (Power Supply Unit) converts AC power from the wall to DC power for your PC components. Choosing the right wattage ensures stable operation, energy efficiency, and room for future upgrades.
The CPU and GPU account for 80-90% of total power draw in most builds. A mid-range gaming PC with a 105W CPU (Intel Core i7-14700K) and 200W GPU (RTX 4070 Ti) needs approximately 400W total, making a 550W PSU the ideal choice with 20% headroom.
80 Plus Efficiency Ratings Explained
Why PSU efficiency matters for your electricity bill
The 80 Plus certification measures how efficiently a PSU converts AC wall power to DC power. A 90% efficient PSU drawing 400W from components pulls ~444W from the wall — the extra 44W is lost as heat.
| Rating | 20% Load | 50% Load | 100% Load |
|---|---|---|---|
| 80 Plus | 80% | 80% | 80% |
| Bronze | 82% | 85% | 82% |
| Silver | 85% | 88% | 85% |
| Gold | 87% | 90% | 87% |
| Platinum | 90% | 92% | 89% |
| Titanium | 92% | 94% | 90% |
80+ Gold is the best value for most users — it delivers 90% efficiency at 50% load with only a small price premium over Bronze. Platinum and Titanium only make sense for 24/7 workstations where every watt saved compounds over thousands of hours annually.
Popular CPU & GPU Power Draw
TDP reference for common processors and graphics cards
Processors (CPU)
| Model | TDP |
|---|---|
| Intel Core i5-14600K | 125W |
| Intel Core i7-14700K | 125W |
| Intel Core i9-14900K | 125W |
| Intel Core Ultra 9 285K | 125W |
| AMD Ryzen 5 7600X | 105W |
| AMD Ryzen 7 7800X3D | 120W |
| AMD Ryzen 9 7950X | 170W |
| AMD Ryzen 9 9950X | 170W |
Graphics Cards (GPU)
| Model | TGP |
|---|---|
| NVIDIA RTX 4060 | 115W |
| NVIDIA RTX 4070 | 200W |
| NVIDIA RTX 4070 Ti Super | 285W |
| NVIDIA RTX 4080 Super | 320W |
| NVIDIA RTX 4090 | 450W |
| AMD RX 7600 | 165W |
| AMD RX 7800 XT | 263W |
| AMD RX 7900 XTX | 355W |
* TDP = Thermal Design Power (CPU), TGP = Total Graphics Power (GPU). Values are base/default ratings from manufacturer specs. Actual power draw varies with workload, overclocking, and board partner designs.
Common PSU Sizing Mistakes
Avoid these frequent errors when choosing a power supply
Buying way more wattage than needed
A 1000W PSU for a 350W system wastes money and runs less efficiently at very low loads (20-30% load zone). PSUs are most efficient at 50-80% load.
Ignoring GPU transient power spikes
Modern GPUs like the RTX 4090 can spike to 2-3× their rated TDP for microseconds. If your PSU lacks overcurrent protection headroom, this causes shutdowns. The 20% headroom in our calculator accounts for this.
Cheaping out on a no-name PSU
A low-quality PSU can damage components, catch fire, or fail to deliver rated wattage. Always buy from reputable brands with proper 80+ certification and safety certifications (UL, CE).
Forgetting ATX 3.0 / 12VHPWR for new GPUs
NVIDIA RTX 40-series and newer GPUs use the 12VHPWR connector. While adapters exist, an ATX 3.0 PSU with native 12VHPWR is recommended for high-end builds.
PSU Buying Tips
What to look for beyond wattage
Modular vs Non-Modular
Fully modular PSUs let you use only the cables you need, improving airflow and cable management. Semi-modular is a good middle ground.
Single Rail vs Multi-Rail
Single rail is simpler and works well for gaming. Multi-rail adds overcurrent protection per rail, preferred in workstations for safety.
Form Factor
ATX is standard for most builds. SFX/SFX-L for small form factor (Mini-ITX) cases. Check your case's supported PSU size before buying.
Warranty Length
Premium PSUs offer 7-12 year warranties. A longer warranty indicates manufacturer confidence in reliability. Avoid PSUs with less than 5-year warranties.
Frequently Asked Questions
Common questions about PC power supply sizing