When selecting a desktop computer's power supply unit (PSU), which of the following practices best ensures that the system can accommodate future hardware upgrades without immediately replacing the PSU?
Purchase the lowest-wattage PSU available because efficiency decreases as rated wattage increases.
Purchase a PSU whose wattage rating exactly matches the system's calculated maximum draw.
Purchase a PSU whose wattage rating is roughly 20-30 % higher than the system's calculated maximum draw.
Ignore wattage considerations and focus only on the number of SATA and PCIe power connectors.
A common best practice is to buy a PSU whose wattage rating is about 20-30 % higher than the system's calculated maximum draw. This extra capacity, known as headroom, allows for the higher transient power spikes of modern components and provides room for adding more powerful parts later. Choosing a PSU that exactly matches or falls below the current requirement leaves no margin for peak loads or upgrades, while ignoring wattage altogether risks system instability.
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Why is having a power supply with higher wattage important for future upgrades?
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What could happen if I choose a PSU with too low wattage?