Yes you could it and it would be a better use of money than an electric water heater. From my understanding of crypto mining, the energy usage on off the shelf

Yes you could it and it would be a better use of money than an electric water heater. From my understanding of crypto mining, the energy usage on off the shelf machines is usually greater than the immediate value of the coins mined. Using it to heat water could change the economics. As the value of coins is always changing these coins could be held as an investment or coins could become valuable enough that they are profitable from the time of mining. I remember a startup selling cpu based heaters to support cloud services, there could be a similar market for water heaters. If you have a cpu in your house you’re already heating with it whether you know it or not.