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A heat pump is a heating and cooling system that moves heat instead of creating heat directly. In winter, it moves heat into the home. In summer, it can move heat out of the home.
That basic idea applies to several different systems. Some heat pumps heat and cool air directly, like mini-splits. Others heat or chill water for hydronic systems, radiant floors, fan coils, air handlers, domestic hot water planning, or geothermal-style water-to-water applications.
What is a heat pump?
A heat pump is equipment that transfers heat. It does not have to create heat from scratch the way an electric resistance heater does, and it does not have to burn fuel inside the home the way a furnace or boiler does.
The term can describe several types of systems. A heat pump for a house might be a ductless wall unit, a central forced-air system, an air-to-water heat pump connected to radiant floors, or a geothermal water-to-water system connected to hydronic equipment.
That is why the best question is not only "what is a heat pump?" The better buying question is: what type of heat pump system fits the home and the comfort goal?
What does a heat pump do?
A heat pump moves heat where you need it. In heating mode, it collects heat from an outdoor source and transfers it indoors. In cooling mode, many systems reverse the process and move heat out of the home.
Depending on the system type, a heat pump can support:
- Space heating for rooms, zones, or the whole home.
- Cooling through indoor heads, ducts, fan coils, or hydronic air handlers.
- Radiant floor heating when the heat pump makes hot water for hydronic loops.
- Domestic hot water planning when the system is designed with the right tank and controls.
- Boiler replacement or hybrid heating when the building already uses hydronic distribution.
For small spaces, a simple air-to-air heat pump may be enough. For whole-home hydronic comfort, the heat pump needs to be planned as part of a larger system.
How does a heat pump work?
A heat pump uses a refrigeration cycle to move heat. The system absorbs heat from one place, raises or lowers its useful temperature, and releases that heat somewhere else.
In an air-to-air system, that heat is delivered directly into indoor air. In an air-to-water or water-to-water system, the heat is transferred into water. That water can then move through radiant floors, fan coils, air handlers, tanks, or other hydronic components.
This is the core reason heat pumps can be efficient: they move heat rather than relying only on direct heat creation. Real performance still depends on climate, system sizing, water temperature, insulation, installation quality, and the indoor distribution method.
Main types of heat pumps
"Heat pump" is a broad category. These are the main system types a homeowner or contractor is likely to compare.
Air-to-air / mini-split
- What it heats
- Indoor air.
- Best fit
- Single rooms, additions, garages, or smaller ductless zones.
- What matters most
- Simple room comfort, not hydronic distribution.
Air-to-water
- What it heats
- Water for hydronic heating and cooling.
- Best fit
- Radiant floors, fan coils, air handlers, DHW planning, and whole-home hydronic projects.
- What matters most
- System design, water temperature, emitters, tanks, and controls.
Water-to-water / geothermal
- What it uses
- Ground loop, water loop, or another water-side source.
- Best fit
- Hydronic systems where a geothermal-style heat source is practical.
- What matters most
- Loop design, source temperature, mechanical-room planning, and hydronic distribution.
Hybrid system
- What it combines
- Heat pump plus backup boiler, electric heat, or another heat source.
- Best fit
- Cold climates, retrofits, or projects where backup heat is part of the design.
- What matters most
- Controls, backup strategy, and when each heat source should run.
Air-to-air vs air-to-water heat pumps
An air-to-air heat pump heats and cools air directly. Mini-splits are a common example. They can be excellent for targeted comfort in one room or a few zones.
An air-to-water heat pump uses outdoor air as the energy source, but transfers that energy into water. That makes it a better fit when the project needs hydronic distribution: radiant floors, fan coils, hydronic air handlers, buffer tanks, domestic hot water planning, or boiler replacement.
If you are comparing both options, the practical question is simple: are you solving one room, or are you planning a full heating and cooling system?
Geothermal and water-to-water heat pumps
A water-to-water heat pump transfers heat between a water-side source and a water-based heating or cooling system. In many home and light commercial projects, this is the geothermal category: the heat pump works with a ground loop or water loop and connects to hydronic distribution.
Geothermal systems can be very effective when the loop field, mechanical room, water temperatures, and indoor distribution are designed correctly. They are usually more involved than air-source systems, but they can be a strong match for hydronic heating and cooling.
For MBTEK buyers, geothermal and water-to-water heat pumps are most relevant when the project already points toward hydronic equipment, radiant floors, fan coils, tanks, or a full mechanical-room design.
What heat pump system fits your house?
The right heat pump for a house depends on the building, climate, existing equipment, and comfort goal. Square footage matters, but it is not enough by itself.
Use these starting points:
- One room or small addition: an air-to-air mini-split may be enough.
- Whole-home hydronic heating: compare air-to-water heat pumps and confirm radiant floor, fan coil, air handler, or radiator requirements.
- Existing boiler or hydronic piping: air-to-water or geothermal may be more relevant than a basic air-to-air system.
- Domestic hot water planning: choose a heat pump system that can be designed with the correct tanks and controls.
- Larger systems: read the 3 ton heat pump guide and confirm the heat load before choosing equipment.
For deeper comparisons, see the air-to-water vs mini-split guide and the APOLLO installation planning guide.
MBTEK recommendation
Start with the system, not just the heat pump
If you are only learning what a heat pump is, start with the simple definition: it moves heat. If you are choosing equipment, the system type matters more than the generic label.
MBTEK focuses on hydronic heat pump systems. That means air-to-water and geothermal/water-to-water heat pumps are the strongest fit when the project involves radiant floors, fan coils, air handlers, tanks, domestic hot water planning, boiler replacement, or larger whole-home comfort.
- For air-source hydronic systems: Browse air-to-water heat pumps.
- For geothermal-style hydronic systems: Browse geothermal heat pumps.
- For sizing questions: Use the System Builder before choosing final equipment.
- For installation planning: Confirm heat load, distribution, tanks, controls, backup heat, and installer experience.
Buying checklist before choosing a heat pump
Before choosing a heat pump for a house, confirm these details:
- Do you need comfort in one room or the whole home?
- Do you want air delivery, hydronic delivery, or both?
- Do you already have radiant floors, radiators, ductwork, or a boiler?
- Do you want domestic hot water or pool heating in the plan?
- Is geothermal or water-to-water practical for the site?
- What heating load and water temperature does the home require?
- Will backup heat be needed in the design?
- Who will design and install the system?
Conclusion
A heat pump is a system that moves heat. That simple idea can power very different equipment: mini-splits, central air systems, air-to-water hydronic systems, geothermal water-to-water systems, and hybrid designs.
If you are planning a full home heating and cooling project, look beyond the generic term. Choose the heat pump system that matches the building, distribution method, water temperature, hot water needs, and installation plan.
