Water-to-Water vs. Water-to-Air
Geothermal Heat Pumps


If you have been reading about geothermal heat pumps, you may have heard them called water-to-water, or water-to-air. What do water-to-water and water-to-air mean?

What do they do?

Water-to-water geothermal heat pumps heat and cool water, for hydronic radiant systems, or for dedicated water heating in commercial buildings (for example, washing machines in a laundromat or hospital).

Water-to-air geothermal heat pumps heat and cool air, for forced-air ducting systems. In the United States, most homes use forced-air ducting distribution systems, so water-to-air units are the standard type used.

What parts are different?

A water-to-water unit has 2 water coils in it. One is connected to the earth loop, and the other is connected to the buffer tank, and then the hydronic distribution piping. The water in your hydronic piping circulates through this coil and is heated or cooled.

A water-to-air unit has 1 water coil, and 1 air coil. The water coil is connected to the earth loop, and the air coil is connected to your air ducting. Air from inside your home is circulated through this air coil to be heated in the winter, or cooled in the summer.


Water Coil + Air Coil =

Water-to-Air
Geothermal Heat Pump
Water Coil + Water Coil =

Water-to-Water
Geothermal Heat Pump


Are There Any Other Differences?

  • Water-to-air packaged units include the fan assembly inside the cabinet as standard equipment. However, the circulating pumps for water-to-water units are an additional purchase.

  • Water-to-water units may be available in fewer sizes than water-to-air units.

  • Water-to-water units are generally more expensive per ton than water-to-air units.

  • Water-to-water units are more efficient than water-to-air units.