Crypto mining hardware is >100% efficient, as it's exactly as efficient as an electric heater, but also generates revenue. Over time, others make more efficient crypto mining hardware, reducing the yield from yours. This causes your "efficiency" to gradually reduce down to 100%, but no lower.
However, nowadays we have heat pumps, which are also more efficient than our 100% benchmark, and produce additional useful heat.
It also makes the hardware depreciate (simply with the passage of time, but also because of the particular usage), which in practice effects the balance and can easily turn the monetary efficiency into negative.
4+ kWh electric showers are ubiquitous in my country. Literally a dumb piece of metal resistance immersed in water. Anything is better than the current situation. What if it was a processor instead?
What if a bunch of home servers could heat up stored water through their heat instead of just dissipating that energy uselessly into the air?
We'd be getting the heat we need and we'd be helping build a decentralized cash network. We were gonna spend energy heating up stuff anyway. Might as well get some cryptocurrency out of that heat.
https://qarnot.com/en/heating-water/
Not sure if it's even available outside Europe. I wonder if it's possible to somehow replicate this with a home server. How is it pumping the heat out of the components and into the water system?