First post, hello all

I am trying to find out what my options might be for using some sort of heat pump for house hold hot water.

I've seen a few models of heat pump that install on the water heater, but they are all more "self contained" than I would like, and none of them produce as much heat as a standard 5500 watt electric water heater (~18000 BTU). I would like to take advantage of all that free heat in my attic during the summer, but I'm not sure it makes sense to put the entire unit up there. What keeps coming to mind is a water source heat pump that uses an air/water heat exchanger and fan in the attic as its heat source.

Am I limited to the small, self contained units? Thanks for any ideas.