The overall Which? test score is made up of the following star ratings, all determined by our rigorous lab tests.
How we test water flow rate
We measure the amount of hot 40°C water that's delivered through the shower head in one go. In general, the higher the wattage of the shower the more hot water it will produce. Showers scoring five scores produced around a litre more per minute than models scoring three stars.
How we test temperature stability
We test to see how well the shower can maintain a 40C temperature if someone else uses the water supply at the same time.
How we test ease of use
We test how easy the shower is to use and to clean. This includes elements such as how easy the instructions are to follow, how easy the shower head and temperature dials are to adjust and how easy the shower head is to clean.