Heat hot water for house and use forced air ventilation over cheap heat exchanger (vented to outside) for excess heat after that?
Also, could duct the heat into the clothes dryer maybe?
I think Google uses a technique that could be put in this setup: heat the water in the toilet cistern, flushing disposes the collected energy.
Hmm, interesting. At first seems more hygienic but on second thought, it might make it extra-aromatic when depositing bodily excretions into the hot water. Perhaps not a big deal though.
But given that water has a high specific heat, that could be a way to dispose of a lot of excess heat.
I would use it to heat up my swimming pool instead of the 400,000 BTU propane heater I have on it now.