Maximum Power (Watts)
|Maximum Power (Watts)||
Simply enough, the maximum power listed for a PSU is its maximum combined output wattage that the device is able to spit from all rails in ideal circumstances. Efficiency comes into play here, but we'll talk about that in more in the 80 Plus definition. Many users grossly over-estimate the required size of a gaming power supply, so we always suggest running your components through a power supply calculator first (though they also over-estimate, in general).
The formula for wattage is voltage*amperage=wattage. Different components in a PC require different amounts of power. For example, an i7-4790k will use approximately 90 Watts at full load, but factors such as turbo boost, overclocking, and throttling can all affect this. Similarly, a GTX 970 can use 145 Watts but, like the i7, this depends on load level, boost clock, overclocking, and throttling.
Power supply vendors all spec their PSUs differently, but there are some general rules we can draw. Power supplies are generally the most efficient when at 60-80% load (at the low-end, a disproportionate amount of power is consumed in the transformation - at the high-end, heat generation eats up the efficiency). For this reason, it is recommended that buyers try to keep their hardware on PSUs that are rated for roughly 20% more power than the system would natively utilize. We talk about this more in the 80 Plus definition.
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