Total peak draw = (CPU peak W) + (GPU peak W) + 75W (other) Recommended PSU wattage = Total peak draw × 1.5 Why 1.5x? Capacitor aging, transient spikes (GPUs can double their rated draw for 1ms), future upgrades, and keeping fan quiet.
Wattage differences aren't just "bigger number better." Correct wattage = enough headroom for transients + peak efficiency at your actual load + quality components. When in doubt, go one tier higher than calculators suggest – but never buy a sketchy high-wattage PSU over a reputable mid-wattage unit. power supply unit psu wattage output differences