Whole life cost performance of domestic rainwater harvesting systems in the United Kingdom

Rainwater harvesting (RWH) can be used to reduce the demand for potable mains water. At the single-building scale, previous research has focused on water-saving potential, while financial assessment has either been omitted or considered in an ad hoc manner. This paper reports on the application of a more rigorous financial analysis of domestic RWH systems than had been conducted previously. Whole life costing was selected as the most appropriate financial assessment technique. A total of 3840 domestic system configurations were assessed at a daily time step, taking into account various stakeholder perspectives and future cost scenarios. In each case, it was found that harvesting rainwater was significantly less cost effective than relying solely on mains-only water. The domestic RWH systems generally resulted in financial losses approximately equal to their capital costs. Without significant financial support, domestic RWH is unlikely to be cost effective for all reasonably foreseeable scenarios.