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.

Other energy uses

The options included on the "Other energy systems" page vary between single dwelling and multi-dwelling projects.

For single dwelling projects the options included are:

  1. Type of cooktop/oven.
  2. Whether the refrigerator will be well ventilated.
  3. Outdoor clothes drying line.
  4. Indoor or sheltered clothes drying line.

For multi-dwelling projects the options included are:

  1. Outdoor clothes drying line.
  2. Indoor or sheltered clothes drying line.
  3. Air conditioner zoning

In multi-dwelling projects the cooktop/oven and well ventilated refrigerator options are available on the Appliances tab.

Alternative energy

What is an Alternative energy supply system?

Alternative energy system means a system which generates electricity on the land the subject of the application, using an energy source other than the electricity supply grid, and includes a photovoltaic power system and a wind generator.

In multi-dwelling developments co-generation systems are also an alternative energy supply option.

The alternative energy system must be located on the same piece of land as the proposed development.

Pools and spas

BASIX assesses the energy used for pools and outdoor spas based on:

  • the type of pool heating;
  • whether or not the pool pump will be controlled by a timer;
  • the type of spa heating; and
  • whether or not the spa pump will be controlled by a timer.

Other pool and spa details (including size and whether or not there will be a cover) are required in the water section of BASIX.

See also Pools and Spas (Water Use)


BASIX assesses the energy used by lighting based on:

  • whether there will be direct natural light available to bathroom/toilets and kitchen;
  • if there is artificial lighting, which rooms will be primarily lit by fluorescent or LED lamps and if these rooms have dedicated fluorescent or LED fitting.


You need to provide adequate ventilation to your bathroom, kitchen and laundry. In multi-dwelling developments, the ventilation system for common areas also needs to be considered.

The available options are different for:

Heating and cooling

BASIX assesses the energy used by the main heating and cooling systems for the living room and the bedrooms. Secondary heating (for example, a fireplace in addition to air-conditioning in a living room) is not considered.

BASIX recognises the following types of heating:

  • gas fixed flued heater – with appropriate star rating
  • gas hydronic system – gas-heated hot water piped to underfloor system and/or radiators
  • 1-phase air conditioning – with appropriate star rating or range of energy efficiency ratio (EER)
  • 3-phase air conditioning - with appropriate EER range
  • heat pump hydronic system – hot water from heat pumps piped to underfloor system and/or radiators
  • air-conditioning ducting only
  • electric floor heating – electric underfloor heating
  • wood heating (single dwellings only, not multi-dwelling developments)
  • central heating systems – multi-dwelling developments only
  • no active heating

BASIX recognises the following types of cooling:

  • ceiling fans*
  • evaporative cooling
  • ceiling fans + air-conditioning*
  • 1-phase air-conditioning – with appropriate star rating or range of energy efficiency ratio (EER)
  • 3-phase air conditioning - with appropriate EER range
  • air-conditioning ducting only
  • central cooling systems – multi-dwelling developments only
  • no active cooling

*Provided ceiling fans have not been included in the Simulation method thermal comfort assessment.

As well as the individual systems listed above, central heating systems and central cooling systems are also an option in multi-dwelling projects.

The estimated demand for active heating and cooling is calculated from the dwelling characteristics and climate zone entered in the BASIX Thermal Comfort section. If no active heating or cooling is selected where there is a heating or cooling requirement specified in the thermal comfort section, the dwelling is assumed to use some form of portable or retro-fitted heating or cooling systems. 

The option of 'air-conditioning ducting only' is for those situations where, usually due to construction costs, the owner will not have the air-conditioning unit 'engine' installed by the time the Private Certifying Authority is due to issue the Occupation Certificate. This allows the home owner to reduce initial construction costs, but still recognize an advantage in BASIX from having an air-conditioning system that will be installed a short time after occupation.

When the option 'air-conditioning ducting only' is selected, the efficiency of the air-conditioning unit will default to the lowest value. When installed, the air-conditioning unit is likely to be rated higher than the default value.

Design principles

BASIX encourages you to reduce your energy use and greenhouse gas emissions through the following strategies:

  • Hot water systems – reducing the demand for hot water (by improving water efficiency) and meeting the demand with less greenhouse-gas-intensive water heaters
  • Heating and cooling – reducing the heating and cooling demand (by improving thermal comfort performance) and meeting the demand with less greenhouse-gas-intensive appropriate heating and cooling systems
  • Ventilation and exhaust – using natural ventilation where appropriate, and reducing the operation of mechanical ventilation with suitable controls
  • Lighting – using direct natural lighting where appropriate and energy-efficient lighting
  • Pools and spas – choosing less greenhouse-gas-intensive water heating and pumping systems
  • Alternative energy sources – such as photovoltaics, wind turbines and cogeneration
  • Other energy uses – choosing less greenhouse-gas-intensive cooking facilities, refrigeration, clothes drying and appliances (appliances are an option in multi-dwellings only – not single dwellings)
  • Central systems (in multi dwellings only) – central hot water, central heating, central cooling, lifts, saunas and other measures


Bottled gas is a valid option in BASIX for applications such as cooking, heating and hot water heating. Gas (mains or bottled) appliances score well in BASIX due to the low greenhouse gas intensity of gas compared to electricity.

For specific information on applications of Gas and BASIX, please consult the following sections:


The Energy section of BASIX aims to reduce the greenhouse gas emissions of all new residential dwellings. The benchmark is 3,292 kilograms of carbon dioxide per person per year, which was the average for pre-BASIX homes.

The energy target ranges from 10% to 50% reductions from the benchmark, depending on the climatic zone and the building type. The BASIX targets are determined from data provided by state and federal energy and water utilities, as well as long-term climate data from the Bureau of Meteorology.

Energy consumption and savings will be assessed on: