Sounds like Triton are sailing pretty close to the wind regarding the trades description act by specifying 8 L/min when that is unobtainable under normal usage. If my calcs are right, you'd only get that if you set the shower to 23°C...
Nope, physics hasn't changed since you did your degree.
As you can see from the table half-way down this page (based on 42°C outlet temp and an optimistic 240V across the heater)...
I'm looking at having a 10.5kW Triton ENVi electric shower installed in my new extension. However the specs don't seem to add up.
The specs say 8 L/min and 10.5kW... Now assuming the mains water is at about 7°C and I want a 38°C...