If you can leverage the earth’s tendency to resist temperature change in order to build a better heat pump, would it be outrageous to think you could use water to do the same thing? Turns out, water-source heat pumps are already a thing and a good thing at that. Water-source heat pumps are actually a type of geothermal heat pump. Keep in mind that all heat pumps also provide cooling so it’s more useful to use the terms ground-source heat pump and water-source heat pump to distinguish between them.
In a water-source system, as you might have guessed, heat is exchanged with a nearby body of water, the depths of which tend to remain at a near-constant temperature just as ground temperatures do, according to Cielo. This is done via a network of pipe coils that capture the heat in water or a refrigerant. This has all the environmental and cost-saving benefits of ground-source heat pumps, but some downsides as well. Of course, water-source heat pumps are only viable for people who live near, and have legal access to a water source. Cheaper than ground-source systems because no digging is required, water-source systems are still more expensive than air-to-air systems.