In a semi-instantaneous water heater, how much water can be stored based on its heating capacity?

In a semi-instantaneous water heater, the design allows for the heating of water on demand while also having the capability to store a small volume of heated water. The typical storage capacity reflects the amount of water the unit can provide based on its heating capacity and the flow rate at which hot water is delivered.

The correct answer indicates that the water heater can store 10 to 20 seconds worth of water. This range is representative of the typical performance of such water heaters, which efficiently heat water as it flows through the device, but also capably maintain a small reservoir of heated water to meet demand quickly. This immediate access to hot water helps in applications where there is a consistent or sudden demand for hot water, as in residential or commercial settings.

Understanding the semi-instantaneous nature of the heater helps in visualizing how it operates—it continuously heats on demand without a large storage tank, thus optimizing performance while still providing a brief supply of preheated water. This balance between access to heated water and on-demand heating capacity is a key characteristic of this type of water heater.