IIRC some combis have a small buffer of hot water to avoid running the tap. Eco mode disables this so you waste water but save on gas.How does a combi heat water in the background anyway, it comes in via mains and goes out at the same pressure, unless you have one with a water tank?
Just had my first bill through. I randomly clicked on the EON Next app on the 6th Sept and saw I could get a tariff with lower charges so opted into it (odd?).
Seems low given I must have charged the car 3 or 4 times and I've been running the hot water off of the immersion heater.