A low-cost hot water use warning device, having the shape of an aerator housing, including a metallic housing inner core (2) with threads configured for attachment to a faucet and a ridged indented channel for accommodating a thermochromic belt (6) or band that may constitute several layers including an outer thermochromic layer (10) capable of changing its color at a certain temperature, a second high thermal conductivity layer (11) made of copper for evening out temperature gradients and a third low heat conducting polymeric layer (12) for imposing a controlled delay. At each vertical side of the thermochromic belt are flanking wedge-shaped isolation grooves (7). The device operates as an awareness indicator for informing a faucet user of excessive temperature and duration of hot water use.