I'm toying with the idea of using a Bitcoin miner to heat water (for domestic use) with excess electricity from a PV installation.  The goal is definitely to just use it when heat is needed and spare electricity is available, and not to run it always.  I'm not trying to maximise mining profit, but just do a fun project that has some useful purpose, too, but obviously I don't want to just burn a lot of money.

I can take care of all the control aspects easily, but I'm trying to determine whether or not there is suitable mining hardware available at all.  Basically I would need a miner with these properties:
- low power, 500-1000W intake
- can be watercooled easily (I'm not too much of a hardware tinkerer, so fitting some pre-made watercooler onto the board is the most I can do)
- cost in the $500-$2000 max range
- does not need to be the most efficient available, but obviously if it only makes $10 a year, there's no point

Does anything like this exist?  I've seen that there are watercooling solutions for S19's, but they draw a bit more power than I want to give it based on my estimates.