It's dependent on incoming water temperature, and the temperature rise desired, and flow rate. As well as the plumbing layout for the home. some homes have the plumbing so spread out that two heaters of whichever kind work best. But, you also don't use it like a conventional tanked where you over heat the water and then use cold to throttle it back to make the hot water last longer. You want a 103 degree shower, you have it heat to maybe 105, and add very little cold water. It does take some changes of habit to get used to it, but you will love it. I've had my 199K BTU Myson almost 19 years now, and expect at least that much more service from it. It's long since paid me back for choosing it, and I can still enjoy any number of back to back 40 minute showers if I want.

That's exactly what I wanted done (install a small, no more than 5 gallon, hot water heater but for some reason due to space and other plumbing & wiring issues that seemed not to be such a great idea. Although at that price, I can't imagine why not. I did find information about something called a Hot Water Heater Scale Inhibitor System (sold at www.plumbingsupply.com along with the Chronomite Instant-Temp Tankless Electric Water Heaters, which is what we have). Anybody have any experience with that unit?

You want to do a few things with locating your heater: 1. locate it so that it can be vented in an approved way (you can't locate the vent too close to windows, doors, etc.) 2. Locate it so that the vent run is short as possible (a few feet is good) if that's not possible, consider a condensing unit that vents with PVC. Stainless Steel venting is VERY expensive. A condensing unit adds several hundred dollars but can be cheaper than a long run of SS vent 3. Locate the heater close to where the water is being used. I was able to locate my heater 20' closer to the bathroom than it was. You can't vent the tankless through an existing flue and you sure can't vent it into a shed. Why can't you vent it to the sidewall? How close is the neighbor's house? You want to mount the unit inside unless you have really mild winters. For mild winter areas they have external installed units. Both interior and exterior have freeze protection, but that should be a fallback protection system. Here is a link that might be useful: See Pg 12 for venting locations

I installed a tankless 6 years ago and will never install a tank again. I did it myself and will do it again if I am ever in a new house. I have a 120k Noritz unit that performs flawlessly. I just don't get it guys. Installing a tankless without recirc is like trying to start your car with a half dead battery. Really! "Your builder is right, it defeats the purpose of tankless" nonsense! I did not have recirc initially. I learned by experience you do not just replace a tank with a tankless. It is a bad result for hot water supply. Slow and inconsistent. Internal recirculation tanks might help but never having used one I have no opinion. But unless you circulate water and insulate your pipes to maintain the heat you are really missing the boat. Recirculating inside the heater means your pipes are cold and it takes longer to get to a tap because unlike a tank there is no pressure in the lines to radiate towards the taps. Why store water inside your heater when you need the heat in the pipes for faster delivery? That is just a limited solution to the issue in my opinion. How much does it cost to keep the lines hot. Depends on heat loss and vol. of water in the lines. Insulate!!! I would say my pipes take very little in cost to keep hot. Maybe $5-7 a month. I used 3/4 inch pipe for recirculation to store more water for start up and to feed 110 degree water into the heater. I do not have a timer to shut off recirculation at night so I could save a few bucks if I did that. Its a simple thing to lay out. You go to the last tap in the system and put a return to the heater from there. You need to have a cold water supply for the recirculation. A one way check valve between the recirc and the street supply prevents hot water from pumping back to the street as hot water pressure rises. A second check valve goes between the last tap and where the street supply feeds the recirc line to prevent cold water pressure from the street from back flowing through the hot water lines. Why any builder would not just put a return line back to the heater is beyond me. Its really not a lot of extra work. Especially with all the cheap Pex being used now. A small grundfos 1/25th hp pump is all that is needed in most cases. I use a Honeywell aquastat to trigger the pump. The pump engages maybe once an hour for maybe a minute to raise the water temp from 105 to 110. Heat loss? Did you insulate the pipes you say are losing heat from? You can lnstall a timer to turn off recirc in the night so you use no energy at all. You can do the same during the day when you are not at home. For some families you could have a daily timer that changes recirc to match your schedule. The hot water works with the recirc off, it just does not work properly as iz well known. Tankless is a superior technology. I did not think the endless supply would matter to me, its noticeably better. A tank cools as soon as you start using water out of the tank and cold water replaces it. The temp drops and drops the longer it flows. A tankless heats water on demand and it is maintained at the same temp. Its really is an advantage. But, as has been stated here by users, un managed hot water supply sucks and who cares if it costs a little bit of money to heat and pressurize your pipes so hot water is instant. Its way less expense than keeping 40 gallons of water hot in a tank. I would never heed the advice by someone on this thread that you don't need recirc. Have your builder install a true full house recirculation system. Don't pay attention to this "you don't need it stuff." If the builder balks or talks down to the idea get someone who knows what they are doing to come install it and over ride their obstinate attitude. Just do not listen to the talk of having a better system is not needed. You are going to great expense to have the best hot water supply you can have. Don't let someone with out your best interests in mind wreck your enjoyment of a great tankless system. Recirc all the way!!! Gee people, why would anyone not do this in new construction when its way easier to do.