A study (April 2007) by Marsden Jacobs Associates was prepared for the Australian Conservation Foundation, Environment Victoria and the Nature Conservation Council of NSW.
This research focused on the impact of a potentially targeted rainwater tank roll-out in Sydney, Melbourne and South East Queensland in comparison to other ‘conventional’ water supply options such as new dams and desalination plants.
This study compares the yield and levelised cost (i.e. the direct cost per kilolitre supplied) of each supply option.
The study recognizes the broader cost savings of rainwater tanks to the community such as deferred water infrastructure, savings to stormwater infrastructure and environmental externalities such as the cost of greenhouse gas emissions.
The study found that:
- Rainwater tanks are cost competitive with dams and desalination plants.
- Rainwater tanks are five times more energy efficient than desalination plants (rainwater tanks requiring 1 MWh/ML compared to typical desalination plant of 5 MWh/ML) and twice as energy efficient as the proposed Traveston dam.
- If governments deployed rainwater tanks to 5 per cent of households each year in Sydney and South-East Queensland, dams and desalination plants planned for 2010 could be delayed past 2026 (Sydney) and 2019 (South East Queensland).
- A preliminary estimate of the cost of a 5 percent rollout would be approximate $200-$280 million per annum in Sydney; $180-$250 million per annum in Melbourne and $140-$200 million per annum in South East Queensland.
- Most Australian houses are suitable for a rainwater tank. In Sydney 65 percent (or 1.1 million houses), in SEQ 73 percent (or 900 000 houses) and in Melbourne 72 percent of existing houses have the potential for a rainwater tank.