Hot water systems can be categorised based on:
- Mode of operation– storage or instantaneous (continuous flow)
- Heat source– solar, gas, air and electricity
Mode of operation - storage vs instantaneous
- Storage systems operate by heating and storing water in an insulated tank. Some of the energy used by these systems is lost as heat dissipating from the storage tank.
- Instantaneous (continuous flow) systems heat water as it is required and do not use storage tanks. The system senses when taps are turned on and it then begins heating the water. Typically 1-2 litres of water pass through an instantaneous hot water system as it heats up, creating a short delay in hot water delivery.
Solar water heaters use solar collectors to heat water in a storage tank. A solar system with a high STC rating will give the best BASIX score. To ensure adequate hot water at night or on overcast days, solar water heaters are often "boosted" by gas or electric heaters. Solar (gas boosted) will usually outperform solar (electric boost) in BASIX.
Gas water heaters can be either storage type or instantaneous. A high efficiency gas hot water system with a high star rating will score well in BASIX.
Air-source water heaters typically use an electric heat pump to move the heat from the air to the water. These are appropriate for warmer climates. An electric heat pump hot water system with a high STC rating will also score well in BASIX.
Electric water heaters can be either storage type or instantaneous. They use the supplied electricity to directly heat the water. Although common, these are the most greenhouse-gas intensive and are the lowest scoring water heater in BASIX. Electric hot water heaters are not an option in the BASIX Alterations and Additions tool