AFAIK PC power supplies are actually one of the most efficient power supplies out there so I'll use them as a reference. The Titanium class of power supplies is

AFAIK PC power supplies are actually one of the most efficient power supplies out there so I'll use them as a reference. The Titanium class of power supplies is around 94% efficient at 100% load and 90% at 20% load [1]. On the other hand plain old transformers start at around 95% and can go even higher. Random internet source claims that it can be 98.5% efficient [2]. Of course you cannot run your computer at AC. I had mostly grid-scale equipment in mind. I just wanted to use something relatable as an example. [1] https://www.velocitymicro.com/blog/what-is-psu-efficiency-and-why-is-it-important/ https://www.velocitymicro.com/blog/what-is-psu-efficiency-an... [2] https://www.electricaleasy.com/2014/04/transformer-losses-and-efficiency.html#:~:text=Transformers%20are%20the%20most%20highly,transformer%20by%20using%20output%20%2F%20input https://www.electricaleasy.com/2014/04/transformer-losses-an....