Hot water systems

BASIX recognises the following types of hot water systems:

  • Solar – flat plate panels or evacuated tube collectors (gas or electric boosted)
  • Heat pump (air source for all dwellings or ground source for single dwellings only)
  • Gas – instantaneous or storage
  • Wood combustion (in single dwellings only – not multi-dwellings)
  • Electric – instantaneous or storage (in new dwellings, and alterations and additions, if offset by solar PV)


If ground source heat pump is selected as a primary hot water system (not pre-heating), no other hot water systems must be installed.

Central hot water systems are also an option in multi-dwelling projects.

For the average NSW home, hot water is responsible for the largest share of greenhouse gas emissions. The BASIX energy score measures greenhouse gas emissions, and so hot water systems with low greenhouse gas emissions score the best in BASIX. The predicted greenhouse gas emissions take into account both the efficiency of the hot water system and the greenhouse gas emission intensity of fuel used by the system (electricity, gas, wood).

Solar – the most efficient hot water system

The most efficient, individual hot water system to install is solar. A solar system with a high number of Small-Scale Technology Certificates (STCs) will give the best BASIX score. Solar (gas boosted) will usually score better than solar (electric boost).

After this, select either high efficiency gas (instantaneous or storage) or an electric (air or ground source) heat pump hot water system to achieve a high BASIX score.

For gas systems, the higher the gas star rating, the more efficient the hot water system, and the better it scores in BASIX.