Its all about getting educated on how they work and what size you need.

They are a great system and they will do what you want, but you have to purchase the right size.

Also get a “name” brand and not something that you won’t be able to find next year.

as long as the lines are not froze they work just fine in any temp.

I have heard that they will flow slower when they have to bring the water up more meaning that it takes longer to heat the water to the specified temp.. Some units will only heat the water within a specific range say 55 degrees. What I mean is that if your water is at 60 degrees it will bring it up to 115 but if your water is at 35 it will only bring it up to 90. They make larger, more powerful units for cold climates that should work. Remember that water freezes solid below 30 so the water entering your system will be no colder than that. Look for a system rated for cold climates with the maximum temperature gain.

foreverhotwater.com tankless water heaters will heat water to temperature you set by remote control. If you want to take 105F degree shower, you set temp to 105! You don’t have to turn on cold to mix with hot. heater will send you the hot water that you set t-stat at, it will restrict the flow in order to heat water to desired temp, so winter temps will restrict it more than summer