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BASIX Cost benefit analysis summary

Since 2004, BASIX has influenced the design and construction of over 150,000 new dwellings. In 2009 the Department of Planning & Environment (then the Department of Planning) commissioned an independent economic evaluation of the program's performance, and its expected future benefits to 2050.

The BASIX Post-Implementation Cost-Benefit Analysis was based on seven case studies determined from actual BASIX certificates in different locations across NSW. It concluded that BASIX has and will continue to reduce water consumption and greenhouse emissions across New South Wales, and delivers substantial economic benefits to BASIX-compliant households and the State.

BASIX saves New South Wales money

The analysis estimated that to 2050, new BASIX certified dwellings will generate a positive benefit to New South Wales of between $1.20 and $1.60 for every dollar spent complying with BASIX, most of which accrues directly to individual householders through lower energy and water bills. To 2050, the total net benefits (minus compliance and administration costs) of BASIX for NSW are estimated to lie within a range of $294 million to $1.1 billion. Forty-six per cent of these benefits will be from BASIX certified dwellings already approved for development. This amounts to an average saving for NSW of between $6.7 million and $25 million a year in lower household bills, emission reductions and avoided electricity network augmentation. The estimated range of benefits is quite broad. This is due to the uncertainty surrounding energy uses attributed to factors outside the scope of BASIX commitments, especially the increasing number, use and energy requirements of portable household appliances, particularly televisions and computers, and the variable energy use behaviour of heating and cooling systems. The graph to the right shows that household electricity bill savings were the chief source of net benefits to NSW.


Household benefits and costs

The cost for a dwelling to comply with BASIX ranges from between $1,114 (for a Sydney high rise unit) and $21,902 (for a single detached house in the Southern Highlands with no gas). The compliance cost for an average Sydney Western Suburbs house was estimated at $6,417. The total per dwelling benefits expected to accrue to households is estimated at between $3,273 (for a Sydney high-rise unit) and $14,661 (for a large Sydney house relying on solar power to pass BASIX) to 2050.

The following graph shows that with access to reticulated gas, most dwelling types can expect to have their investment returned through energy and water bill savings (see full report for details of non-gas and large house case studies).

Untitled-13Costs and benefits of BASIX compliance to 2050 

Key findings

Large houses are at a significant disadvantage in BASIX due to their high energy and water consumption, with a large 400m2 house in Sydney estimated to cost over 2½ times that of an average Sydney house (240m2) to meet the same BASIX water and energy targets.

Substituting electricity with gas fuel sources is the most cost-effective approach to meet BASIX energy targets. Access to gas reduces BASIX compliance costs by around 40 per cent for new houses and between 85 per cent and over 300 per cent for new units.

  • BASIX compliance costs are lower for unit dwelling types, which have lower energy targets and are able to distribute costs over a greater number of dwellings.
  • The higher single dwelling compliance costs reflect the added cost of individual rainwater tanks included by most single dwellings to satisfy the BASIX water reduction target.
  • Compliance costs outside of Sydney are higher due to greater installation costs, lack of reticulated gas access and climate variables often requiring greater system efficiencies (such as thicker insulation in colder regions). 
  • Costs of compliance for units are slightly higher than estimates made when BASIX was first introduced in 2004. This reflects a wider investment in system and fixture efficiency to meet improved energy, thermal comfort and water targets, as well as an improved understanding of compliance pathways in multi-dwelling developments. 
  • The BASIX scheme promotes innovation in the design of water and energy efficient technologies and practices, and assists in the further growth and development of these industries in New South Wales. 
  • The cost for reducing one tonne of carbon emissions through the BASIX scheme is $0, as the households are generally better off through lower bills that offset the costs involved. 

Future improvements

  • The report's findings indicate that there is a clear need to obtain an improved understanding of the impact of BASIX and other energy efficiency initiatives upon household energy use. 
  • In order to maximise its effectiveness, BASIX should be continuously updated to ensure new energy and water efficiency innovations are taken into account.

    The BASIX Post-Implementation Cost-Benefit Analysis was conducted by NERA Economic Consulting and BMT Quantity Surveyors.
    BASIX® is a registered trademark of the Crown acting through the NSW Department of Planning & Environment.

2006 - 2009 Multi-dwelling outcomes

BASIX is the NSW Government's residential sustainability program for all new housing in the State. Under BASIX housing developers are obliged to commit to water and energy-efficient building designs before development approval is granted.

This document summarises the 2006-09 BASIX Multi-Dwelling Outcomes report and presents the sustainability commitments made in NSW for all new residential developments of more than one dwelling between 1 July 2006 and 30 June 2009, including units, townhouse rows and subdivisions.

The impact of BASIX is most evident in the increased use of alternative water sources, particularly water tanks, in most new dwellings, the greatly decreased use of inefficient
electric hot water systems in new homes and high NatHERS Star Ratings reducing the energy required to heat or cool the home.

46,000 new multi-dwelling homes

improved by BASIX

61% of new multi-dwellings use

alternative water

130,000 bottles of water saved

every year in each multi-dwelling

99.8% use gas, solar or heat pump

hot water instead of electric

203,000 tonnes of greenhouse gas

already saved

5.25 average NatHERS star rating

for BASIX multi-dwelling


Since October 2005, all new residential developments of more than one dwelling have had to meet mandatory water and greenhouse gas emission reduction (energy) targets of up to 40 per cent from an average pre-BASIX NSW home.†

BASIX has improved the sustainability of 4,753 new multi-dwelling developments in NSW, comprising over 46,000 individual homes.

Unique sustainability tool for large developments

BASIX has designed separate tools for single and multi-dwelling developers because energy and water consumption patterns vary significantly between these types of developments. The BASIX Multi-Dwelling Tool includes technologies specifically suited to larger residential developments, especially for unit blocks with common areas such as car parks, lifts and shared gardens which can require significant amounts of water and energy.

Over 60% of all BASIX multi-dwelling homes were units in residential flats.

The importance of a specific tool to deal with units is illustrated in the large proportion of unit homes certified by BASIX, reflecting trends in NSW housing development towards denser dwelling types (see following graph).

outcomes multi_1Multi-dwelling homes certified by BASIX during the reporting period 

NSW Green State targets

The NSW 2010 State Plan committed the State to 60 per cent emission reductions by 2050, and saving 145 billion litres of water a year by 2015. New BASIX multi-dwellings are predicted to have already saved around 6.5 billion litres of water and up to 203,000 tonnes of greenhouse gases.

Savings from multi-dwellings are equivalent to the water used in over 2,500 Olympic swimming pools and the annual emissions of over 9,000 cars for five years

The average BASIX multi-dwelling home is predicted to use 78,000 litres less potable water and emit 2 fewer tonnes of greenhouse gases per year than an average pre-BASIX home. This is roughly equivalent to every new multi-dwelling saving 130,000 bottles of water a year and around 50 per cent of an average car’s annual emissions.

BASIX reduces water consumption

Majority of multi-dwellings connected to an alternative water supply

outcomes multi_2Alternative water use in BASIX multi-dwelling homes 

94 per cent of multi-dwellings with alternative water used rainwater tanks - before BASIX was introduced, only around 12 per cent of all NSW dwellings had rainwater tanks.

61% of multi-dwellings now use a tank or recycled water supply rather than mains water for part or all of their toilet, laundry and irrigation needs

Many unit blocks may not connect alternative water directly to individual dwellings, but instead reduce water consumption by connecting tanks or greywater systems to irrigate shared gardens. For units in residential flat buildings, 73 per cent of shared common gardens use an alternative water supply for irrigation.

Water-efficient fixtures and appliances in all homes

Australia’s Water Efficiency Labelling Scheme (WELS) requires clothes washers, dishwashers, taps, toilets and showerheads to be registered and rated according to the amount of water they use. The minimum WELS rating for toilets and taps is now three stars, but around 50 per cent of all new multi-dwelling homes commit beyond these standards to taps rated four stars or higher, and over 40 per cent committed to toilets rated four stars or higher.

BASIX homes reduce water demand with taps, toilets and appliances beyond minimum efficiency standards.

outcomes multi_3BASIX multi-dwellings with taps and toilets rated 4 stars or higher. This graph shows that growth in high performance taps and toilets has steadied, indicating further stringencies may need to be introduced to improve fixture efficiencies further.  

For units in residential flat buildings, committing to water-efficient dishwashers and clothes washers can contribute to meeting BASIX targets. Minimum WELS performance standards on installed appliances have yet to become compulsory in Australia, but 31 per cent of clothes washers and 38 per cent of dishwashers installed to BASIX units had a rating of four stars or higher. The lowest available product for both has a rating of one star.

BASIX reduces greenhouse emissions

Phasing out emission intensive electric hot water systems.

The following graph shows how new BASIX multi-dwellings are phasing out high emission electric storage and instantaneous hot water systems. These systems were used in 67 per cent of existing pre-BASIX homes in NSW, and now feature in only 0.2 per cent of new multi-dwelling homes.

outcomes multi_4Hot water systems in BASIX multi-dwellings 

18% of all BASIX multi-dwelling homes now use solar energy for hot water compared to only 3% of preBASIX homes

Reducing the need for heating and cooling through good building design

BASIX calculates how much energy is required for heating and cooling a dwelling based on the design and construction materials of a new home, such as insulated ceilings and walls or performance glass installed to better retain and deflect heat.

Improving these features can contribute significantly to meeting BASIX energy targets as over 13 per cent of average emissions in pre-BASIX homes were attributable to heating and cooling the home.

Securing the sustainability of shared facilities and common areas

Pre-BASIX data indicated that up to 50 per cent of per capita emissions for a high-rise unit dweller were attributable to common area energy use. The primary contributors were continuous car park ventilation and round-the-clock incandescent or halogen lighting.

The following graph indicates some of the key improvements new developments are making to common areas to improve BASIX scores.

outcomes multi_5Common area efficiency improvements 

Committing units to energy efficient appliances

71% of multi-dwellings commit to an energy rated dishwasher 63%

commit to a rated clothes

51% commit to a rated clothes washer 39% commit to a rated refrigerator

BASIX Co-generation demonstration project

The BASIX Multi-Unit Residential Cogeneration Demonstration Project is an initiative of the Department of Planning & Environment and involves partnership with residential development companies Lend Lease GPT and Mirvac. The purpose of the project is to trial and showcase cogeneration technology in a residential setting, with a focus on reducing energy consumption and greenhouse emissions.

About the project

The Cogeneration Demonstration Project features the installation of small-scale, gas-fuelled generators in a 7 storey Lend Lease development at Rouse Hill in western Sydney, and in Mirvac's 25 storey Cambridge Lane apartment building at Chatswood in northern Sydney.

The generators are powered by natural gas with an electrical output of 25 kW. They are able to supply a modest part of the electrical demand of each building, which is used in common areas. It is the cogeneration function that provides significant greenhouse emissions abatement, by making use of the heat that is a by-product of generator operation. At the Lend Lease and Mirvac developments, this heat will be used to provide approximately two thirds of the hot water needed by the residents, saving around
80 tonnes of carbon dioxide per year for each site.

Initial results

Initial performance results show that cogeneration can achieve significant savings in both greenhouse emissions and costs. After eight months operation (mid-December 2007 to mid-August 2008), cogeneration at Mirvac's Cambridge Lane development is saving its occupants around $1,000 a month on power bills. By generating its own hot water and common area electricity, the apartment block has also cut its greenhouse emissions by 53,594kg. The potential saving for a year at this rate reaches 120 tonnes of CO2, equivalent to greenhouse emissions from around 35 cars.

The cogeneration technology has also proven cost effective to install. It is estimated that the Chatswood generator would pay for itself within 12 years, well within its 25-year expected lifetime. At Rouse Hill, lower building occupancy and a later start-up date mean that the cogeneration performance is still being tested.

co-gen diagram 1 









Performance monitoring

The Department of Planning & Environment is monitoring the performance of both sites for a year from the commencement of cogeneration. Specialist project managers, MPI, are involved in managing the systems to find maximum efficiencies. The first eight months of reports for the Chatswood site are available below:

What is cogeneration?

Cogeneration is the simultaneous production of two useful forms of energy, such as electricity and high temperature heat, also known as combined heat and power (CHP). By harnessing more energy from one generation process, cogeneration increases energy efficiency and can reduce greenhouse gas emissions when compared to other power systems. The generator can be located close to where the energy is needed, enabling local or building-based systems to control their own power.

Cogeneration has been applied around the world in a variety of industrial and commercial settings. In some larger applications, the heat can be used for space cooling as well as for water and/or space heating (trigeneration).

co-gen diagram2










co-gen diagram3