Hi, needing to get a thermostatic electric shower to deal with flow variations when other taps are turned on. Currently have a 9.5kw shower which sometimes goes cold. It's receiving about 9l/min of cold supply, so if I put a 10.5kw shower in, would the flow be insufficient, or would we just get more flow out due to the increased heating capacity? In other words, do bigger heating capacity showers require a higher inflow rate to avoid over heating or something? Thanks
No. If I were you I'd install a 12kW one. I've had all 3 (9.5, 10.5 and 12), and 12 is the best by far.
Just make sure the cable, the MCB/RCBO and the overhead switch in the bathroom supports the higher current load.