You can use the heat pumps, powering them with 50amp shore power, or running the generator. They will function as long as the ambient temperature is 43 degrees Fahrenheit or more. I have always played safe and turned them off when the temp falls below 45.
They are not connected in any way to the Hydro/Aqua Hot. Separate units.
P.S. I read somewhere that Aqua Hot is now offering to rebuild Hydro/Aqua Hot units. In the past they claimed it couldn't be done.