In Europe and Asia, there were over 2 million air-to-water heat pump systems installed in 2016. In the U.S., there were about 1,000 installed, says John Siegenthaler, instructor of HeatSpring’s “Applications of Air-to-Water Heat Pumps for Hydronic Heating and Cooling,” and other courses.
“That market is going to grow,” he says. “Air-to-water heat pump systems are definitely a growing market sector today in North America.”
Air-to-water heat pump systems are growing in popularity in part because geothermal heat pump systems, now subsidized by the federal government, are considerably more expensive than air-to-water systems. And those geothermal subsidies are expected to be phased out by 2022, which will allow air-to-water heat pump systems to enjoy a competitive pricing advantage.
Air-to-water heat pumps are generally a third to a half of the cost of a typical geothermal heat pump system, says Siegenthaler.
Energy-Conscious Vermont Provides Subsidies for Air-to-Water Heat Pumps
In addition, energy-conscious states are starting to view air-to-water systems as worthy of subsidies, as evidenced by Vermont’s recent announcement of a subsidy for air-to-water systems.
Another important factor makes air-to-water systems advantageous: the comfort they provide in a building, says Siegenthaler, Professor Emeritus of engineering technology at Mohawk Valley Community College.
“The big differentiator between a ductless mini-split heat pump and an air-to-water heat pump is the comfort they deliver. With a high-performance heat pump combined with a hydronic delivery system, you get a really great match there,” he says.
One example is an air-to-water heat pump tied to a radiant floor delivery system. This would provide both energy efficiency and superior comfort, he says. And this type of system has advantages over air-source heat pumps.
All air-source heat pumps must occasionally defrost their outdoor heat absorption coil. With a ductless mini-split heat pump, the heat for defrosting comes directly from inside air, which can create uncomfortable conditions inside a building, he explains. With an air-to-water heat pump, the heat comes from a buffer tank or from the heated floor slab. Occupants will not feel this, so comfort is not compromised, Siegenthaler says.
Health Benefits of Air-to-Water Systems
What’s more, a radiant floor delivery system–or any water-based delivery–is healthier for occupants than forced-air heating systems. That’s because forced air systems often push mold, pollen and other lung irritants through their ducts.
Air-to-water heat pumps are also capable of heating domestic water, a load which cannot be handled by ductless mini-split heat pumps.
Americans Need to Be Choosy About Heating Systems
In spite of all these options and benefits, many Americans aren’t aware of the benefits of air-to-water heat pumps. While they’ll generally take the time to look at options in wood flooring or cabinets–choosing carefully–they often don’t shop for heating systems. They just accept whatever contractors suggest, which is generally the least expensive option–forced air.
“Most Americans have no idea that their homes can be much more comfortable than what the average American consumer accepts,” says Siegenthaler. “Forced air systems as a whole just do not create the favorable comfort conditions that hydronic radiant systems do.”