yes i read about a swimming pool heated with a crypto mining rig - i like that idea a lot.  however modern heating technology is based on heat pumps which are at least 2X more efficient than resistive heating.  mining rigs are resistive in terms of their performance as heaters. 

 Heat pumps use compressors only? No heating elements? 

 heating elements may sometimes be used to defrost the coils in winter but for the most part yes - heating pumps are based on compressors.