Hi, about 3 years ago we had a plumber carry out a new boiler installation & a new bathroom which included replacing an old Mira shower with the above Aqualisa. While the unit is still under guarantee in the past year we've had 3 failures when power is interrupted to the unit. The digital unit & pump is in the loft (almost above the actual shower head & control unit) and this is on it's own circuit. What happens when the unit gets a power glitch (either isolating the circuit by RCB or a minor fluctuation - by minor like today power blipped only 2 devices had an issue - the oven clock & the Aqualisa - even the broadband router didn't duck out) is that it locks into boost mode & despite following all the instructions previously supplied by Aqualisa, the device cannot be re-set. The last two engineers replaced the control unit that allows you to switch the shower on and that resulted in a fix & worked until the next power failure. The boost option is really not used by us very much, apart from taking considerably more water (& power to re-heat) it is of little benefit. When the next engineer arrives I'm afraid I will not let he/she go until we've tried a simulated power failure, but I wonder why this might be happening. I'm somewhat disappointed because this product is not exactly cheap. Some friends have recently installed a newer version & have experienced problems and are waiting for an engineer at the moment. Any input to this issue gratefully received.