How is a PSU rated ?
How is a PSU rated ?
The specific make and model of the PSU are not provided in the information given.
A very good question. My assumption seems to be just a matter of convention.
In the auto trade, it's typical to state the engine's output at the crankshaft, though the actual power reaching the wheels is reduced because of transmission inefficiencies.
https://www.motortrend.com/how-to/modp-1...power-loss
"Strap your 298hp Rev-Up G35 Coupe to the dyno and you might be let down to see only 220 to 230 horses at the rear wheels."
As an electronics design engineer, I focus on the total power consumed, including PSU losses, to accurately define mains wiring and circuit breakers, but as @Nigel Spike points out, most home PC builders are more concerned with the power drawn by individual components.
In this case, the 500W rating applies during continuous operation. The 625W represents maximum output (such as during a surge or spike). All ratings are determined for continuous use.
The wattage capacity listed indicates how much power the PSU can provide to components in DC, but it doesn't reflect the actual power drawn from the wall because of inefficiencies in converting AC to DC. Additionally, the calculations provided are incorrect.
This information might help some with background details. Keep in mind the links provided.
The power rating mentioned can be risky for those unfamiliar with it. A 700W unit might pull more than 800W from an outlet. If the room’s capacity is around 1500W and you run two 700W computers, what happens?
My living room usually handles up to 1500W, but I’ve experienced power drops when running two or three 700W machines at once. I didn’t realize it until I read an article (the link was gone).
I believed a 500W supply only draws 500W, but that’s not true.
The sudden power surge when a switch is activated can sometimes cause circuit breakers to trip, fuses to blow, or switch contacts to wear out due to arcing. "Inrush current, or switch-on surge, describes the peak, immediate electrical draw by an appliance at the moment it powers up. Sufficient inrush can trigger breakers and fuses, harm switches, relays, and bridge rectifiers. Therefore, minimizing the inrush current during startup is ideal." The surge in this Thermaltake Toughpower 1050W PSU is even greater, reaching 152.7 Amps at 230V AC. https://hwbusters.com/psus/thermaltake-t...-review/6/ It only consumes "800W" from the outlet when fully loaded to its 700W capacity. Such high demand is rare unless the PSU has sufficient power margin. Most ATX units rarely operate at their full rating, except during controlled lab tests. A good practice is to select a PSU with several hundred watts of reserve. For a 700W unit, it's wise not to build a system requiring more than 500W. If you hook up a Killawatt meter to a standard PC, the reading will stay under 200W until intense gaming or video editing begins. Most systems draw between 60W and 150W during startup and idle, despite having higher PSU ratings like 650W, 750W, or 850W. What might occur? Likely nothing unless the ATX switch-on surge activates the room breaker. A poorly designed PSU paired with a sensitive main breaker increases the risk. I can power six computers in one room without any issues, all running smoothly. My most powerful machine draws only 420W from the mains when pushed hard. Since I don’t have an RTX 5090, the CPU uses 170W and the GPU 200W.
Yes, but many older apartments (even new ones) lack sufficient power for power-hungry devices. One of the No Fuse Breakers in my apartment sometimes shuts off when my air conditioner, microwave, toaster, and computers activate together. That’s why I pay attention to how much electrical power is being used.