Rainwater harvesting (RWH), which was previously undertaken more out of necessity than any commitment to autonomy, is now being heralded as a sustainable alternative for domestic water supply and flood control, and in disaster relief. In Trinidad and Tobago and the wider Caribbean region, RWH is included in water security and sustainability strategies. Despite the plethora of domestic RWH projects, estimates of water consumption in RWH-dependent households are unavailable, and project designers are left to assume values that are based on conventional water-supply systems. In the present study the per capita consumption (PCC) of domestic water in three RWH-dependent communities was quantified. For this purpose, households' perceived and actual water consumption was investigated in three rural communities in Trinidad. It was found that perceived and actual consumption are 105-164 l per person per day (lpd) and 95-240 lpd, respectively. Householders' perception of how much water is consumed was generally significantly different from the measured amount. While the sample of measured PCC was small, the results provide more realistic values for the design of RWH systems, which are being promoted in the region.