8.5, 9.5 or 10.5kW Shower?

[Zerax]

Common misunderstanding is that electric shower use electric to increase pressure, as explained in post unless shower is pumped before or built in pump the pressure will dependant on pressure on cold feed, the kw is rating of element and is somewhat pointless as i do not see anyone using a 8.5kw on full hot setting so no point fitting a 10.5kw over the years i have worked out people think the higher the kw the more the pressure this is clearly not so.

Well....yes... and no. I agree about pressure... but it's really the flow that's important. The more power that's available, the more water can be heated to the same temperature. From my experience, this is most notable in the winter when the water is often just above freezing... takes alot of power to raise the temperature up to about 40°C. The water flow rate will be reduced to keep the outlet temperature high enough.