Domestic hot water (DHW) production is a significant portion of energy and water use in buildings, especially as space heating demand declines in high-performance envelopes (e.g., Minergie, NZE buildings). Showering alone accounts for 50 L per use, and newer “eco” showerheads advertise flow rates of 5–12 L/min—much lower than the 12–25 L/min of standard models—suggesting potential savings of 50% or more. But do these claims hold up? This study evaluates the actual performance of 24 water-efficient and standard showerheads by measuring flow rates under constant pressures of 3 and 1.5 bar and assessing rinsing efficiency by quantifying shampoo residue rinsed from a mannequin head with human hair. Results show that rinsing efficiency does not correlate with flow rate, as 22 out of 24 models, including eco models, required an average of 27 L of water to rinse shampoo effectively. These findings challenge the assumed water and energy savings of low-flow models, as longer rinsing times negate their benefits. While eco showerheads reduce flow rates, their real-world impact on water and energy savings is limited unless rinsing performance is addressed.