Moving to 12-volt rails makes a big difference in energy efficiency.

Intel’s latest power play isn’t about toppling AMD, but about energy efficiency. The company’s new ATX12VO power supply standard is designed to help desktop PCs meet increasingly stringent government standards on idle power consumption.
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https://www.pcworld.com/article/3576039/intels-power-play-hands-on-with-atx12vo-motherboards-and-power-supply.html