> By design, it's enormous electric heater.

You're right, it's not leaking, it's dumping excess heat on purpose.

However, I get triggered whenever someone uses the term "by design" wrongly. The generation of heat is not by design. It's an undesired side-effect of the computing being done. "By design" would mean that someone decided that there should be a certain amount of heat generation and made sure that it happens.

Most often I see this term misuse from developers who explain bugs as being "by design". It happens when two features interact in an undesired way that creates problems (a bug). Developers like to look at feature A in isolation, determine that it works as designed, then look at feature B, determine that it also works as designed, then they look at and understand the interaction between feature A and B and since they now understand what is happening, they claim it's "by design". However, nobody ever decided that feature A and B should interact this way. It was clearly an oversight and every normal person would agree that the interaction is undesired and a bug. But the developer says "won't fix, this is by design". Infuriating!

When you compute some nice and elegant result, dissipated heat is an undesired side effect. But let's face it: we are speaking about proof of work. Proof of work means that a computed has run during some "required" time. In other words, you have to prove that enough heat has been dissipated. Waste of energy actually is "by design" here.