Some Australian water businesses are implementing a range of alternative water supply schemes in an attempt to conserve centralised supplies of potable water. However, the justification of alternative schemes often relies on best guess potable water savings, alternative source demand values and cost components. Seeking a more rigorous assessment process, this study followed an evidence-based approach in accordance with Step 5 of the Australian integrated resource planning (IRP) framework, whereby scheme water consumption was monitored through end-use studies and costs were evaluated using actual cost and performance data. Such detailed evaluations can extract accurate total resource perspective unit costs ($/kL) of alternative water supply schemes and better inform decision-making.