Size a power supply from component draw with headroom and efficiency.
Modern GPUs produce transient spikes well above their rated draw, which is why headroom is a stability requirement rather than future-proofing. Running near 50 per cent load also places the PSU at its efficiency peak. Transient spikes trip protection circuits on marginal supplies, producing shutdowns under load that look like GPU faults rather than power problems.
PSU Wattage
Recommended rating = component draw × (1 + headroom); wall draw = draw ÷ efficiency
Recommended rating = component draw × (1 + headroom); wall draw = draw ÷ efficiency Modern GPUs produce transient spikes well above their rated draw, which is why headroom is a stability requirement rather than future-proofing. Running near 50 per cent load also places the PSU at its efficiency peak.
Transient spikes trip protection circuits on marginal supplies, producing shutdowns under load that look like GPU faults rather than power problems.
This calculator takes 5 inputs: CPU power draw, GPU power draw, Other components, Headroom for transients and upgrades, PSU efficiency at load. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.