Savings from showerheads occur due to a reduced flow rate using less water and requiring less energy to heat said water. However, measuring these water and energy savings is complicated by a host of unpredictable behaviors that there is currently insufficient data to account for. At the last discussion of this measure at an RTF meeting in 2016, residential showerheads were changed from proven to planning in response to this uncertainty.
Main areas of concern were the lack of metered retrofit studies on the subject, questions about the relationship between flow rate and energy/water use, and the impact of installation/removal rates on savings. More research is needed as the RTF currently does not have sufficient data to reliably estimate either physical savings for installed low-flow showerheads or the installation and removal rates associated with common delivery channels. More information about that proposed research can be found in the residential showerhead research strategy.