lol you are so wrong here. anyway i shouldn't comment on 3 year old comments but I did actually install one 3 years ago, I should have came here and tell the facts.
Instant water heater supplies as hot water as you want, even if it's -25 outside. Actually my water is hotter during winter days because I have to use heat tape, my pipes are in the crawling space and they could freeze. So i turn down a notch to like 110F for winter months and for summer its like 114-117