I've just had a shower (Mira Sport 9.8KW) and accidentally left it on the medium setting (about 20amps drawn). Surprisingly, it was quite hot, so the incoming mains water must be warming up nicely. Are there any data to show how the temperature of mains water varies with outside temperatures? I'm in London, so I suppose that makes a difference (micro-climate etc.). The shower companies must have researched this though. Just interested in saving money.
