We are installing two in our new build. Now we have not moved in yet as we are not that far. The gas guy told us it will pay for itself within a year or two. Since natural gas wasn't available we had a propane tank installed. DB, who is an electrical engineer, swears by the tankless hot water.

We have a Bosch. Won't choose it again.

Normally there are just two people here, but when we have a house full of guests, I love that we never run out of hot water. But we're extremely disappointed that it won't hold a steady temp while we shower. It "fires up" then goes off, and as it does that, the water gets hot, then cold, then hot again. We didn't install thermostatic valves -- I guess that would have made a difference. We didn't have the problem with our conventional HW heater so never thought of it.

When our GC contacted Bosch about this, their only suggestion was "turn down the water temperature." That didn't solve the problem, and besides, who wants to live with warm water instead of hot?

I don't know if this is an issue with all tankless heaters or if it's just Bosch, or just ours, but our new house will go back to the conventional tank system.

That's interesting to know. Can someone with a different brand or with the thermostatic valves chime in here? Would love some expert advice since we're considering going tankless in a new build with the Rinnai system.

We have an on demand water heater in our shop building. I like it just fine, but I am not showering out there, just using kitchen sinks for stuff like canning and clean up. Keep in mind that it hogs power. We had to add power to the building to accommodate it. It is expensive to put in, but I am sure it pays for itself quickly. We didn't have a water heater out there to begin with, so I can't give you figures for savings.

The house we are currently renting has a tankless water heater. I had planned on having one in our soon to be built home, but not anymore. My husband and I just hate it as mid shower the water starts to cool down and goes completely cold. With conditioner still in one's hair , it's huddle in the corner and turn it off, then back on again to get hot water. sometimes this works right away othertimes it takes awhile until you get the flow just right! Our architect told us that the correct size and different brands factor in. We will be going with a regular hot water heater in the new house.

Hi - we've been in for a year now, with two tankless (Takagi) gas heaters and I would go with them again. Our gas usage is less than the townhouse we lived in during our build, and we have two children at home. We do have thermostatic valve on all showers, so that may make a difference. We also use multiple applications at once (diswasher and washer and shower) with no real problems. Good luck.

A little OT: I read of an engineer who installed a holding tank in the basement. Water comes into this tank very cold from the city water main. It warms up quite a bit within the basement before going into the water heater. I didn't read this until after we'd built, but it sounds interesting.

We have a Noritz N-069M. It just serves 2 bathrooms- we added on and put in the new heater to be close to the points of use. Kept the old heater in the garage on the opposite side of the house.

The shower that gets the most use has a Hansgrohe thermostatic valve. The heater is set at 105F, which is plenty hot for even my steamy-shower-loving wife. At the warmest point of the year (July/August), the hot water demand may drop low enough to cut off the burner. That happens 5-6 minutes into the shower. And not every time. That we had a solid month at 100F in ATL this year may also have been a factor.

The simple solution would be to remove the 2.2 gpm flow restrictor, but we won't do that since we got the tankless in part to save water.

The current Fine Homebuilding has an article on installing tankless heaters with storage and/or recirculation. The suggestion for hostagrams and emilynewhome's problem is to put a small electric tank heater downstream of the tankless to buffer the cold water.

It's really intended to catch the cold water between 2 showers as the burner lags for a second in firing up as the 2nd shower starts. Your problem sounds more difficult- either the unit just doesn't handle single-shower flow, or you really should set the temperature even lower (really, 105F is plenty hot). FWIW, the largest Bosch tankless has a burner about the same size as the smallest Noritz (Takagi and Rinnai cover a similar range, IIRC).

As for it paying for itself quickly- I kind of have a hard time buying that. For us, putting it outside also meant no expensive vent pipe and no indoor real estate occupied. The value of the latter is kinda hard to quantify.

But the cost of the larger gas line (marginal unless you're having to replace), vent pipe and install to me pushes the marginal cost up a good bit over a standard heater. Tax credits and/or utility rebates may make up some of that difference. A higher-efficiency tank heater would cost more, but then it's more efficient, so the extra cost for tankless takes longer to get back in reduced energy usage.

And I have no idea about propane- think if that's your only gas option, you really should compare the cost vs. electric (which needs a great big wire to do tankless).

We have a Rinnai tankless water heater that supplies the master shower and bath and the guest bath. Also have an electric 50 gallon heater for the laundry, kitchen, and other baths. We love it. Whenever we take a shower or bath, we never ever run out of water. We've never had the problem of hot water/cold water. It remains hot when turned on and when we turn on another faucet, the temp does not change. We do have a thermostatic grohe valve however on the shower. Our monthly gas bill over the summer for the tankless and the stovetop was never more than 15 dollars a month. We never run out of hot water in the other side of the house as well.
Good luck.

Thank you all! Seems the Rinnai has no problem, but it could be the thermostatic valve mentioned. I would think any of the manufacturer's would recommend the pros/cons or significance of this valve, no? I mean if you're investing more money in a product which is *supposed* to be more efficient, and provide instant hot water, the manuf. needs to take responsibility if other requirements are necessary.

For those who did not have the therm. valve installed, what was your reason for making that choice? Was it not recommended? And is one needed for each shower OR barhroom? What about the DW~ample hot water? Washing machine, too? And do valves need to be installed on all these appliances, too? TIA

If Bosch said it is working properly when you said "It "fires up" then goes off," then something is wrong and that may explain why we had the same issue with the water in the guest shower going cold in a rental we used to have while we were building. It was Bosch too. I always thought it was a faulty thermostatic valve in the tap, and that the Bosch was too sensitive.

The burner should not go off if the minimum GPM is flowing -- period. That's how a tankless works -- forever.

Water flow passes the minimum GPM, the burners ignite and heat the water to the set temp as flows thru. As long as it continues to flow above the minimum GPM, then the burner does not go off and water is heated to the set point.

BUT, if you have a faulty thermostatic valve in the tap, and it gets water that is too hot coming to it, it is going to crank down the hot-flow and turn up the cold-flow. Your shower starts to cool. And, when it cranks down the hot-flow, that in turn could send the flow below it's GPM minimum thru the tankless, thus exacerbating the issue and quickly freezing you out.

Then it starts over again.

That sounds like your issue w/ the Bosch and I'm sure it was our issue in the rental. We have never seen such in our new home and we have Hansgrohe and Delta, w/ the Takagi.

Another happy Rinnai owner here. We have two of them, one on each side of the house so as close to points of use as possible. We have endless hot water at a constant temperature. Houseful of guests or just the two of us, the water is always there and just right. Love 'em!

When correctly sized for water demand most owners of tankless water heaters are very happy with their choice.
I've seen quite a few installs that the problems were solved by the install of a larger unit.
Its been kind of funny in my area to see how tankess gas units have been selling so well and with so few complaints.
I remember several years ago talking with the local supply house about stocking a .82 energy factor gas tankless units and being told that "they don't work" now the supply house keeps a regular stock of tankless gas units.
And the plumbers now know how to install them!

I'm not a big advocate of the electric units. Given my energy perspective..it is just not economical. I think someone posted early in the thread with a electric unit.
I understand that it takes at least 90 amps for a tankless elec unit to operate.
Many homes have had to add to their electrical service to
power these units.
My area's utility rates vary from a modest .08 cents per Kwh to a very high .13 cents per Kwh.
I don't recommend electric, but the gas units.

Also I believe that there is an Energy Star tax credit or rebate for some of the higher energy factor gas units.
energystar.gov has more info..

Good luck to all of you in your projects.

I have an electric tankless. The brand is no longer on the market, company is out of business, so if/when it dies I'll have to replace. I didn't choose it, it was already in the house I bought. I was leery of it at first, but have found I like it enough that I'd probably replace it with another tankless.

Whole-house electric can pull a lot of amperage if running at full capacity (mine is 120 amps) .. but they *don't* run at maximum output unless required to meet the heating demand. I've often seen mine run at only 7% to 35% of full capacity. Wiring for sufficient electrical capacity is easy on a new build, can be problematical on a retrofit ... which I suppose is one reason why gas is more popular. There's no gas in this house, the only choice would have been propane, so electric is it.

It seems counter-intuitive, but for those having trouble with temperature swings or concerned about the possibility ... the solution is either DON'T use thermostatic shower valves with a tankless, or DON'T set the unit too high. LOWERING the temperature of the tankless WILL help keep output temperature stable by allowing the shower to run at a higher flow-rate so the tankless doesn't shut off for lack of flow. I set mine at between 100°F (summer) and 103°F (winter), so that for showering I run ONLY the hot water. I've NEVER had trouble with temperature swings. I raise it temporarily for tasks needing higher temps. It's in a broom closet in my laundry room, easily accessible for adjustments, and the electronic control panel automatically reverts back to the normal setpoint after 30 mins (or 15 mins, 45 mins, or 60 mins per the programming). Many units nowadays allow for remote controls to facilitate adjustment from bathrooms, kitchen, etc., particularly handy if the unit is installed in a location that isn't easily accessible.

I was curious when I saw so many replies..

Where did you tankless gas people locate your unit?
Would you move it?

A lot of installs I see are located in the attic, thankfully now there are pans under these units as a common install.
Several homeowners have told me that the cost of the venting pipe is quite expensive. Depending on roof pitch the number of pipe sections will change.

Has anyone located their tankless gas on an exterior wall?
I like the idea and the homeowners that I work with that did install in this location really liked it.

What are y'alls thoughts and/or experiences?

Both of our LP gas Rinnai's are located on exterior walls. The controls are in the master bath and under the kitchen sink - very accessible if needed. It is a perfect arrangement for us.

Ours is located on a wall in the big storage area under the stairs going to the second floor. But it was a new build, so planning it for supply air and exhaust stack was easy.

We have 2 SETS electric tankless heaters. We had problems upfront with a (separate) part on each of the units that SETS had to replace. The company worked with DH and GC who ran "tests". I think SETS was great in taking care of both units in a fast manner. That doesn't mean we don't have current issues though. We are on well water on the side of a mountain and have a sediment issue we're trying to resolve. A softwater system was installed and we've also added a filter at the well itself. These tankless units need a certain amount of water flowing to maintain the heating. If it doesn't we get that hot/cold scenario. If there is sediment in the line we don't get the water flow needed to run these units properly.

I have the Takagi TKD-20 in my house, have been living there for over two years now. I would definitely install another one. However next time I would use a smaller unit (this one is 186K BTU, after living with it I certainly don't need this capacity).

The people that have identified that their units switches off, and they get cold water during a shower, are because they have the wrong size units installed, or they simply are not adjusted properly. These units turn off if there is insufficient flow, on mine if the hot water draw is below 1.1 gpm it will switch off, a function of the size of the unit I purchased. However the "proper" way of adjusting it is so that when you take a shower, you use hot water only (it is really not terribly efficient to heat water at 86% efficiency only to cool it with an addition of cold water anyway, especially when this causes you to use less hot water, perhaps below the amount the unit needs to flow). Those of you with electric units don't have this problem, as the big ones I have seen take eight breakers and any of these ciruits can be switched on or off by the controls. The gas units don't have that level of control on the burners.

Another thing to consider is that if you have a big tub with a roman tub faucet (mine flows 16 gpm), the tankless unit will restrict the flow of hot water so that it reaches its temperature setpoint, mine is sized to flow around 7 gpm at my coldest intake temperature, so yes it takes a bit of time to fill this big tub. However at 16 gpm, you are going to drain a conventional system very quickly anyway.

Would I do it again, it definitely meets my needs. Please note that you will also have problems if you get a conventional tank HWH that is improperly sized, either too large or too small - also understand that you don't get 40-gallons of hot water out of a 40-gallon tank because for every gallon you take out (hot), it gets replaced with another gallon from your intake (cold). With either type of unit, ou need to understand the capabilities of the unit and what your expctations are so they can be sized properly.

And to answer ERLA, mine is installed on an exterior wall (short venting, both intake and exhaust) in my utility room.

We installed a Noritz N-06M on an exterior wall last January. We're in the final stages of a major addition/remodel and only using water in the original bathroom ... the farthest link to the heater. No complaints! It takes a little while for the hot water to reach the bathroom, but that was the same with the old tank unit. Have a remote on the laundry room wall, so any adjustments are easily made.

We have a Takagi, installed during a remodel 6 years ago. Before we had the tankless we would constantly run out of hot water during morning showers (had a teenage boy at home). We have absolutely no problems now - you can run that thing for hours and have hot water constantly. We do have the thermostatic shower valves. Hubby (an accountant and keeper of the bills) said we showed a 20% drop in the gas bill almost immediately.

We would absolutely do it again.