What does the term "hydronic heating" refer to?

The term "hydronic heating" specifically refers to a heating system that utilizes water as a heat-transfer medium. This involves circulating heated water through pipes or radiators to distribute warmth throughout a space. This method is efficient because water has a high heat capacity, allowing it to effectively carry and transfer heat.

In contrast to the other options, hydronic systems are distinguished by the fact that they do not rely on electricity, steam alone, or combustion processes involving natural gas to operate, even though some heating systems may incorporate those elements in different configurations. The focus on water as the primary medium for heat transfer is what fundamentally defines hydronic heating systems.