AC water heater

On a hot day the refrigerant in the coils of the compressor outside can be >130 F. At these temperatures, not only is the AC very inefficient, but a source of heat is wasted.
By putting a by-pass to the outside coils and putting secondary coils in a water filled preheat tank, the refrigerant can dump the heat into the water, warming it. As I mentioned in the previous post every degree you preheat water from ground temperature saves significant energy, and over a day a 6 ton AC unit can easily heat 100 gallons of water to 80 or higher. Using a tankless water heater and given the current cost of a KWH ($0.1) this can result in a savings of $0.6 a day, depending on the location this can be >$70 a year in direct savings. As long as the outside temperature is hotter than the water the AC would continue to use the water jacketed coils. In Houston and Phoenix this can mean final water temperatures above 100 F for several months a year, meaning saving of more than a dollar a day. Combining this with the savings in energy from the AC running more efficiently the yearly savings can double or more.

By making the system about to bypass the inside coils and use the water jacketed coils and the outside coils, the heat pump effect could actually heat the water to usable temperatures during most of the year in a significant part of the country. Yes a heat pump water heater would be a slow way to heat water but it would be an extremely efficient way. In colder areas, where night time temperatures are too low for heat pumps, larger tanks could be heated to 70 or 80 during the day, and then used for hydronic heating through out the night, as a way to supplement a traditional furnace.