Its definately better in a shed or garage in the winter, because if the membranes freeze the water expands and cracks the membranes, then they are screwed! Which at just under £200 a pop aint good. Also the filter housings are really vulnerable if left out in the cold, not so much of a disaster if they crack but still a pain if you cant produce water whilst your waiting for a new one. I use a greenhouse heater in the shed in the winter to kkep my RO toasty when its really cold. But i do live in Wales....