Our 23 birds drink about 2/3 to 3/4 of a gallon a day, total for all the birds. I fill up the 5 gallon bucket about once every 5-7 days. The coldest it's gotten here this winter is +2F, no frozen horizontal nipples. I'm using a 250W stock tank deicer and the bucket is wrapped in aluminized bubble wrap. I used the same system, minus the bubble wrap, last winter down to -9F, no freezing issues. The bubble wrap is probably just going to lower our electric bill a bit rather than keep the HN's unfrozen. The water stays I'd guess about 50F in the bucket, I haven't measured it accurately, only with my hand.
The bedding below the waterer stays dry. This is a nice change from the vertical nipple bucket we used part of last winter in which we had huge mounds of ice (and wasted water) piling up underneath the nipple bucket. The vertical nipples didn't leak per se, but they did dribble quite a bit when the chickens were using them. The chickens also got wet and led to some minor frostbite on combs. I had to refill the 3 gallon bucket for 12 birds every about 2-3 days. That means they went through about 3/4 a gallon of water every day for just 12 birds. I'm using the same if not less now for 23 birds.
@aart , yes they have pecked at the bubble wrap a bit more. It's more a cosmetic thing, I think it's functionality is still mostly there. Perhaps I will wrap it with some fabric or duct tape when I get around to it.