Which type of DHW system is typically energy-efficient and does not have a storage tank?

Tankless water heaters, also known as on-demand water heaters, heat water directly without the use of a storage tank. When a hot water tap is turned on, cold water travels through a pipe into the unit, where it is heated by either gas burners or electric elements, providing a continuous supply of hot water. This system is energy-efficient because it eliminates the standby heat loss associated with traditional storage water heaters, which often maintain a reservoir of hot water even when it is not being used. Consequently, tankless systems can save energy, reducing overall costs, as they only operate when there is a demand for hot water.

The other types of systems mentioned have different characteristics that may not be as energy-efficient or involve the use of a storage tank. Free-standing systems may refer to traditional configurations with storage tanks. Solar systems, while they utilize renewable energy, often require additional components for storage. Inductive is not typically associated with water heating in this context, further distinguishing tankless systems as the most efficient option without a storage component.