Only true for our current computers and not true with reversible computing. With reversible computing you can use electricity to perform a calculation and then "push" that electricity back into a battery or a capacitor instead of dumping it to the environment. It's still a huge challenge, but there is a recent promising attempt:

"British reversible computing startup Vaire has demonstrated an adiabatic reversible computing system with net energy recovery"

https://www.eetimes.com/vaire-demos-energy-recovery-with-rev...

https://vaire.co/

Short introduction video to reversible computing:

https://www.youtube.com/watch?v=rVmZTGeIwnc

I read it as the inefficient part isn't the compute efficiency, the inefficient part is dumping all the resulting heat into the environment without capturing it and using it in some way to generate electricity or do work.

On a related/side note, when there's talk about seti and dyson spheres, and detecting them via infrared waste heat, I also don't understand that. Such an alien civilization is seemingly capable of building massive space structures/projects, but then lets the waste heat just pour out into the universe in such insane quantities that we could see it tens/hundreds of light years away? What a waste. Why wouldn't they recover that heat and make use of it instead? And repeat the recovering until the final waste output is too small to bother recovering, at which point we would no longer be able to detect it.

> every single one of those Joules ends up as one Joule of waste heat.

Yes it ends up as heat, but with some forethought, it could be used to eg heat people's homes rather than as waste.

This violates energy conservation principles. Some power will be "wasted" into heat, some other will be used for some other work.

Interesting question - how much will end up as sound, or in the ever smaller tail of things like storing a bit in flash memory?

Theoretically, if your computation is energy efficient, you won't need any electricity at all since the real computation costs zero energy.

If I turn my fan on and 100% of the electricity is converted to heat, where does the kinetic energy of moving fan blades come from? Even the Trump administration cannot just repeal the law of conservation of energy.