Our bungalow has an electric shower fed by about 10ft of piping in the loft.
I found myself idly wondering just now if I ran the shower without any heating, and took the output temperature, and also measured the loft temperature (which I dread to think !) if I'd get some sort of handle on how efficient the pipe insulation is ?
Presumably another reading of the temperature of the water out of the mains would add something ?