What type of heating system primarily circulates hot water for heating?

The hydronic heating system is the correct choice because it specifically refers to a method of heating that utilizes hot water as the primary medium for heat transfer. In this system, water is heated in a boiler and then circulated through pipes to radiators or underfloor heating elements in the space being heated. This process efficiently distributes warmth throughout the area.

Additionally, hydronic systems are favored for their ability to provide even and comfortable heating, as well as potential energy efficiency benefits compared to other systems. They can also be integrated with various heat sources, including boilers, heat pumps, or solar water heaters, enhancing their versatility.

On the other hand, a forced air system relies on air as the heating medium, involving ducts and blowers to distribute warm air. An electric heating system directly uses electricity to generate heat, often through resistive heating elements, which differs fundamentally from circulating hot water. Lastly, a geothermal system can also be part of a hydronic setup but typically refers to using the earth’s temperature to heat or cool living spaces rather than specifically circulating hot water for heating purposes.