Two operating approaches
- Storage water heating
- A tank keeps a stored volume of water hot. The stored volume, recovery capability and anticipated demand are relevant to comparing an exact unit.
- Instantaneous water heating
- Water is heated as it passes through the unit. The required flow and temperature increase are important when assessing capacity for simultaneous use.
These are general technology distinctions, not a statement that a particular model is in stock. Confirm the equipment and its installation requirements for the actual application.
Describe how hot water will be used
A single point of use and several outlets used together create different questions. Describe the application and which demands may occur at the same time before comparing a unit.
Compare the exact version
Storage and instantaneous equipment work in different ways. For instantaneous systems, required flow and temperature increase are relevant sizing considerations. Use model-specific documentation and professional assessment rather than assuming that a room count identifies the right unit.
Establish the scope of supply
Clarify the manufacturer, model, quantity and included components in an actual offer. Installation conditions and any separate work need their own assessment and arrangement.
Technical background: US Department of Energy: instantaneous water-heater selection factors.