It is well known in the PC hardware enthusiast community that the last few digits of percent of performance come at enormous increases in power consumption as voltages are raised to prevent errors as clock speeds go up.

Manufacturers chase benchmark results by youtubers and magazines. Even a few percent difference in framerate means the difference between everyone telling each other to buy a particular motherboard, processor, or graphics card over another.

Amusingly, you often get better performance by undervolting and lowering the processor's power limits. This keeps temperatures low and thus you don't end up with the PC equivalent of the "toyota supra horsepower chart" meme.

1400W for a desktop PC is...crazy. That's a threadripper processor plus a bleeding edge top of the line GPU, assuming that's not just them reading off the max power draw on the nameplate of the PSU.

If their PC is actually using that much power, they could save far more money, CO2, etc by undervolting both the CPU and GPU.

1400 is definitely the sticker on the side of the PSU. There is some theory behind keeping your PSU at 30-50% for optimal efficiency, but considering the cost of these 1k+ W units You're probably better off right-sizing it.

I myself massively overspec my PSU's for my builds as I want ti keep them in the optimal efficiency range rather than pushing their limits. For a typical 800W budget I usually go with a tier1 1200W offering.

I'm actually using a 1600W PSU. 1400W is my target max draw. This is a dual EPYC (64 core CPU each) system btw. The max draw by the CPU+MB+Drives running at peak 3700MHz without the GPU is 495W! Adding 4x 4090 (underclocked) will quickly get you to 1400W+.