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.

Hi Lisadlu, I guess it went fine....The water went in and it came back out. I didn't really see too much dirty "stuff" in the vinegar bucket, or the rinse bucket at the end. I think there was a little red residue in the rinse water which I think was the from the HOT water hose (it was red). Due to the low amount of "Stuff," either I didn't need to do it, or I didn't do it right. I had read somewhere NOT to turn off the electric, but the instructions in my manual clearly said to turn it off, so I did. I was lucky to have the valves already installed by the original installers. It just made sense to shut off the cold in and hot out, and then attach the hoses and run the cycle of vinegar for an hour or so. I guess the plumbers charge so much because of the time, not the technicality. I wasn't too clear on the rinsing part. I let the cold water run in to the heater and out into a clean 5 gallon bucket, then emptied it and let the 5 gallon fill one more time. I think I was supposed to let that 5 gallon rinse run through a few times, but I didn't see the point. I just let the hot water faucets run for a while. There was a slight vinegar smell when I first turned them on. I did it all by myself! No hubby required. I watched a few videos and consulted my owner/installer manual. I made sure to do it on a Monday and not a Friday in case I @#%$'d it up! (figured emergency plumber on a weekend would cost $$$) Good Luck!

There is a lot of flaming and bashing in the old thread linked by chemocurl. Seems to be standard procedure when tankless questions are asked. Yes, my tankless was installed as part of a new construction finished in mid-2004. I bought the house in January 2005. I did not choose tankless, it was already in the house. I have no idea how much it affected construction costs. Honestly, I was leery of it. Turns out the tankless works perfectly fine. The closest usage point is the washing machine and heated water reaches it in about 30 seconds, a bit longer to reach full temperature. Other usage points take longer according to the distance involved. My house is an L-shape, with the master bath at the long end and guest bath at the short end, the kitchen is a little off-center toward the guest side, and utility/tankless a little further toward the guest side. The distance to the master bath is quite long, and it takes several minutes for heated water to arrive. The distance issue is not directly related to the tankless. It's a "flaw" in the plumbing design and still would be an issue if the one water heater in the house was a traditional tank unit. A possible solution is adding a retrofit circulation pump, which I've considered one suited for tankless situations, but it's only a matter of convenience for quicker access to hot water, which is no big deal to me. Temperature stability is fine, I don't have the variations about which I've heard others complain. I think electric tankless is better than gas for temperature stability in use. I like that I can adjust the temperature to exactly what I need for the task at hand, so I'm not overheating the water and using excess energy. I don't often use it, but I can fill my jacuzzi tub and not have a drained tank that must recover if another heated water task needs to run immediately (or concurrently). I like that hot water does not exist until I need it. I don't have to pay "up front" for 50 gallons of water heated to 120°F or 130°F if I need only 15 gallons of 102°F water for a shower ... but I can get 140°F any time I want it for zapping a load of white clothes. Another thought for people who have youngsters (or elderly) in the household -- being as tankless produces an endless supply of water at "task temperature" and doesn't have to be set higher to insure sufficient capacity as does a tank heater ... the temperature can be dialed-down to prevent risk of scalding.

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.