Hot water systems are categorised based on:
- Mode of operation – storage or instantaneous (continuous flow)
- Heat source – solar, gas, air and electricity
Mode of operation
- Storage systems operate by heating and storing water in an insulated tank. Some of the energy used by these systems is lost as heat dissipates from the storage tank.
- Instantaneous (continuous flow) systems heat water as it is required and do not use storage tanks. The system senses when a tap is turned on and it begins to heat the water. Typically, 1-2 litres of water will pass through an instantaneous hot water system as it heats up, creating a short delay in hot water delivery.
Heat sources
Solar water heaters use solar collectors to heat water in a storage tank. To ensure adequate hot water at night or on overcast days, solar water heaters are often "boosted" by gas or electric heaters.
Gas water heaters use the supplied gas to heat the water. They can be either storage type or instantaneous.
Air-source water heaters (heat pumps) move heat from the air to the water, making them very energy efficient. Efficiency improves in warmer climates.
Electric water heaters use the supplied electricity to heat the water. They can be either storage type or instantaneous. Electric hot water heaters are not an option in the BASIX Alterations and Additions tool
Performance
A hot water system's performance rating varies depending on the technology and climate. While the tool allows you to enter higher performance ratings, it’s important to ensure the selected hot water system and rating can be achieved in your location.