How much headroom should my PSU have?
We recommend 20-30% headroom above your peak power draw. This keeps the PSU in its efficiency sweet spot (50-80% load), provides room for power spikes, and allows for future upgrades. A 750W PSU for a 500W system is ideal.
What's the difference between TDP and actual power draw?
TDP (Thermal Design Power) is the heat the cooler must dissipate, roughly equal to power draw. However, modern CPUs and GPUs can boost beyond TDP for short periods. Actual power draw can exceed TDP by 20-50% during heavy loads.
Does PSU efficiency matter?
80+ Bronze: 82-85% efficient
80+ Gold: 87-90% efficient
80+ Platinum: 90-92% efficient
Higher efficiency means less wasted electricity (and heat). For a 500W system, Gold vs Bronze saves ~$20-40/year in electricity.
Why do GPUs have transient power spikes?
Modern GPUs can spike 1.5-2x their TDP for microseconds during load changes. The RTX 4090 can spike over 600W briefly despite a 450W TDP. Quality PSUs with good transient response handle this; cheap PSUs may trigger overcurrent protection and shut down.
Should I get a modular PSU?
Modular: Only attach cables you need—cleaner build, better airflow, easier cable management.
Non-modular: All cables permanently attached—cheaper but messier.
For most builds, semi-modular (fixed motherboard cables, modular peripherals) is the sweet spot.
How do I measure my actual power consumption?
Use a Kill-A-Watt or similar power meter at the wall outlet. This measures total system draw including PSU inefficiency. Software tools like HWiNFO can estimate component-level draw but are less accurate than wall measurements.