Here some way to make the crypto mining rig more profitable/energy efficient:
https://www.makeuseof.com/tag/build-energy-efficient-ethereum-mining-rig/

https://plus8.net/2017/04/15/crypto-radiator-saving-money-on-heating-by-mining-cryptocurrency-xmrmonero/

For the last link: Maybe in the summertime you can heat clothes/water/food?