There must be dozens of threads with this same title.

Let me ask you: Why are you considering Tankless? Generally there are two reasons - continuous hot water and/or energy savings - which issue is driving you?

I can answer #4 easily. Don't even consider electric whole house tankless. Just don't.

#3: Outside will be fine

#2: Efficiency is a non-brand issue: There are generally two classes of gas tankless water heaters:

A. those that are condensing units (they lower the flue gasses below the condensing point of water vapor). By definition they are 92-96 effecient

B. Non condensing units they are in the 82% -86% efficient range

Most manufacturers make both - I would only consider a condensing unit. The cost to vent them is usually cheaper (vent through pvc pipe) and that makes up for the higher cost. That may be different if it's located outside - but I'd still stick with condensing. There is only going to be a percentage or two difference max between brands in the same class of heater.

As for reliability - you are going to get a lot of opinions on that. I like Rheem

Here's the thing: if you are in Arizona you should at least consider a hybrid heat pump heater. Unit cost is similar to tankless, install cost is less and operation costs generally less - and you get cool dry air as a bonus. Heat pump heaters also set you up for renewable (PV) also.

I just had a Navien tankless water heater installed at the beginning of this year (2019). It is a gas condensing tankless water heater.

Pros:

1. Water gets hot at most of my faucets pretty fast or just as fast as my old tanks used to, but the hot water is more consistent and stays super hot for the whole time I am demanding the hot water.

2. Takes up a lot less space in my utility room in the basement and I don't really fear a major leak happening anymore like I did with my old tanks.

Cons:

1. It's loud. My salesperson and installers did not tell me this could be an issue. Tankless water heaters have moving parts that make noise. My Navien vibrates when it runs and I can sometimes hear it and feel it (like a low resonance vibration). It can sometimes sound like a motorcycle or an idling truck outside. I'm still in the process of seeing if I can insulate the noise. The unit itself has already been inspected by multiple people to make sure it is operating normally.

2. Very expensive initial cost.

2. Most efficient? I think the Navien condensing units are 96+ efficiency and you can get a rebate from your gas company for it. I certainly have not seen a major decrease in my utility bills though. I don't know about most reliable brands. I've heard good and bad about all the top brands: Rheem, Navien and Rinnai.

3. If installing outdoors, that makes having the fresh air intake and exhaust simple (I think? I'm not a pro) and you probably won't hear it either. But they need to be protected from the weather and still need an electrical line. Mine is in my basement and the installers had a hard time finding a clear path for the pvc pipes to get from the unit to the outside and still be in code.

4. I've heard nothing good about electric water heaters.

I've had an electric tankless for 14+ years. I didn't choose it, it was already in the (9 months old, built-to-sell) house I bought. There's no natural gas service in this neighborhood outside town and the builder opted not to deal with propane. So, the house was built with sufficient electric service to handle it.

There are no operational noises.

I have no dissatisfaction with it. There are two whirlpool tubs in the house. I don't use them much but when I do I have no concern for running out of heated water.

Dadoes:

My comments about whole house electric resistance tankless has to do with the fact that there's not generally a reason to do it. The efficiency gain is only a few percent over electric tank and they generally have a much smaller temp rise/gpm rating than gas. The increased electrical service usually makes it prohibitive.

You should also at least consider a hybrid tank heater. It would cost a lot less than resistance heat to operate.

My gas tankless units also make some noise - but not as loud as Erin is suggesting. I hear it click on in the basement right below the bathroom - I wouldn't want it next to the bedroom, but is fine in the basement.

I hear my Navien after turning off a faucet (after the demand for hot water) and it purges the system. Almost sounds like a distant motorcycle driving away. Then when it is doing a re-circulation cycle, I used to hear it very loudly because some of my water pipes where strapped to my duct work in the basement and it was resonating through them. It's mostly fixed now, but I wanted to mention noise as a possible con for tankless water heaters. I had no idea that they would make any noise, so it is something I had to get used to and others considering tankless should be aware of. I would agree that usually you shouldn't be able to hear them as loud as I did.

Thanks to all of you for the inputs.

To me, using tankless water heater is " back to future". I grew up abroad, way back then, it was the default water heating appliance, same as in many other countries I have traveled and lived. I am surprised after all those years, tankless is still not a popular water heating appliance in the USA.

In this "just in time" era, it makes sense to use what we need when we need it, not to mention tankless takes less space. Usually we only have one person lives in the house year around, I thought it is wasteful to spend money keeping huge tank of water hot. Wonderdog asked why I am considering tankess, I thought may be the more suitable question is "Why we are not considering tankless".

Home Depot carries Rheem. The sales person said he has tankless at home. He said when we are ready, HD would help us to identify the preparation and associated cost are required for installation.

I will check with our local gas company to see if there is any rebate, and check other brands. To me, even if the cost is a wash I would go with tankless.

Following.

Jake:

What is a "hybrid tank heater?"

So, you should know that the standby losses of a tank water heater (other than standard natural gas tank heaters) is not that great - about 2-3 %. Gas tankless are more efficient because they utilize much of the heat, resulting in low flue temps... not because they avoid standby losses.

Space savings is a thing.

But, again, you should check out a hybrid tank heater. Other than the space issue, it could be a good solution. It's going to be much cheaper to install than a tankless AND probably less expensive to run. There are often rebates from electric utilities for hybrid tank heaters. The hybrid tank heaters output cool, dry air... a bonus in a hot climate.

Our tankless Navien 240A (gas) was installed at our previous home here in the Phoenix area by Aqua Science and I loved it. It was installed in the garage so I never heard it. I loved the constant supply of hot water as needed. Eventually, I'll have another one installed here in our new home. Highly recommend!

AJCN

What is a "hybrid tank heater?"

It's an electric heater with a tank that uses an air-to-water heat pump to take the heat from the surrounding area to heat the water. It's a hybrid because it also contains electric resistance elements like a standard electric heater if fast recovery is needed.

They generally cost a little less than a gas tankless to operate ($161 vs $190 per year) and are much cheaper to install than gas tankless. They don't produce continuous hot water like a tankless does, but they do get hot water to the faucet faster than a tankless.

They are particularly good in warmer climates because they exhaust cool, dry air. They can help to cool a garage, or dehumidify a basement, for example.

If you don't have natural gas available, they are a particularly good choice. They also are a good match with solar PV systems.

Many electric utilities are offering rebates of $300-$500

drsaj,

Glad you are also in Phoenix area as I do. I noticed Aqua Science has multiple locations, did you use the one in Tempe? May I ask who did the installation in your previous house? Thank you in advance for the inputs.

HU, yes, we used the Tempe location which is their main location. They did the install at our previous home. If you'd like to discuss in more detail, just shoot me a message.

Eek, glad to read some of the positive comments. We just purchased two gas tankless for our remodel. The potential noise issue is spooking me. Our G.C. plans to build enclosures for each (they'll be outside; we're in a very moderate climate) but one is located on a wall separating a bedroom. Can they be sound-proofed fairly well? Yikes.

We chose the propane Rinnai Ru98e and it's very quiet. Our electricity bill reduced so much the electrical company changed our meter thinking something was wrong with it. Tankless is the way to go.

We just switched to tankless after our 14 year old WH died. The cost was higher both equipment and installation cost and it was a pain to install, have a great plumber and he still needed to come out a couple of times to get it right. Don’t notice the noise, it’s out in a garage. The shower gets hot FAST, like 2-3 seconds as opposed to what used to be 20-ish seconds. Haven’t noticed a huge savings in our bill.

drsaj, Appreciate for offering additional inputs. I sent you a message regarding details of installation. Thank you in advance.

Just remember that during use, tankless water heaters use much more energy than a tanked unit. It's the down time that results in a cost savings.

A tankless unit pulls a much larger instantaneous flow of energy (gas or electric) for the duration of its duty cycle than a tank unit pulls for the same period of operation ... because physics.

Increasing the temperature of a given quantity of water from X°F to Y°F takes Z amount of energy, whether that energy is added over a period of (for example) 30 mins or instantaneously (tankless unit).

A tank unit takes longer to heat because it pulls a smaller flow of energy. The large quantity of pre-heated water (30, 40 gallons, more) stored in the tank allows for "reserve capacity" to cover the longer recovery time required to heat the cold incoming flow when heated water is drawn from the tank.

That's why the hot water supply can "run out" when taking multiple back-to-back showers or filling a large whirlpool tub ... the tank unit can't input enough heat at a fast enough rate to keep up with the demand. Tankless can do that.

Which is also why retrofitting a tankless unit to an existing tank installation can be problematic ... requiring an upgrade on the gas or electric service.

Over and out ...

Oh ... just to add ... I'd be interested in a hybrid tank unit but 1) it may not fit in the broom closet where my tankless is installed, 2) there may not be sufficient airflow into the closet unless the door is removed or kept open, and 3) the closet is within the climate controlled envelope of the house so what might be the net effect during winter weather with the hybrid pulling heat into the tank while the HVAC is working to warm the house?

@dadoes - on your question 3, net effect - assuming that what 'hybrid water heater' here means heat pump water heater, and the 'heat' being used is from within the buidling envelope as you described...

...studies I've seen say that the net effect is mostly negative during heating months. On an annual basis, depends how much of the year is heating vs nothing or air conditioning - i.e. in cold climates with little or no air conditioning, it mostly results in more energy usage/cost/climate emissions. In climates where air conditioning common and/or heating months short, usually a net gain.

Big caveat: the studies I saw were mostly for climates where household heat from gas or non-heat pump electricity, or with some significant percentage of electricity generation from fossil fuel thermal. There are more complicated grid/fuel source interactions and I don't want to oversimplify.

Or to simplify: if your climate is cold enough that you hardly use AC, hot water heat pump has to be within the building envelope, and you heat with fossil fuels or resistance electricity or very high % of grid electricity from e.g. coal, net effect probably negative. (Cost in dollar terms may be different, another whole set of factors.

The studies I looked at were mostly cold climates - e.g. Canada/Northern USA - and overall conclusion was heat pump water heaters in buildings heated by fossil fuels were a net negative in most respects (most of these places low AC usage). In places with electric heat, difference was basically between localities with high non-fossil fuel grid electricity (high proportions of hydro or nuclear) - most with high fossil fuel electricity were net negative.

But: from purely monetary perspective, too much variation between electricity/gas prices to generalise. The lower the gas price is compared to electricity price, the more chance it may pencil in.

Final simplification: if your heat pump water heater would be indoors, you heat with gas or other fossil fuels, and you hardly ever use air conditioning, it probably won't be a big advantage or be outright negative in most respects.

Wow, love the science here! My engineer dad would be impressed! :)

I'll take that a sa compliment). I should have said, for those in more mild or hot climates, heat pump water heaters should overall be a pretty big win.

We've had tankless water heaters for 13 years between two houses and wouldn't go back. Advantages are the obvious -- no water tank (we had one leak and it was a nightmare) and endless hot water, even with multiple people showering, laundry/dishwasher going, etc. Disadvantage: the price. A good one is expensive. Don't buy a cheap one, those the ones you see complaints about.

We've had Navien and no complaints -- except for the initial fire up which isn't too bad, you can't hear it outside of the utility room, even in quiet bedrooms. Ours is gas and outside of the winter heating months, we have pretty low gas bills. Our current house is in the Pacific NW, other house was in Dallas; both installed indoors.

We’ve put Rinnai tankless gas water heaters in our last 2 homes. My Dad has had his Rinnai for 12 years and has had zero problems. We have no noise issues - I simply never hear it. The only con I can think of is the initial cost of installation.
Ours is in the garage. The master bath is on the other side of the house, so the plumber installed a recirculating pump which provides instantaneous heat to that bathroom. We just have to flip a switch in the bathroom 1 minute before we need hot water for our showers. We could just forgo the switch, but then we’d have to leave the water running a bit before it was hot enough and I hate wasting the water.

Moved into a multi level TH with gas tankless hot water heater a couple of months ago. Love it so far. On the 4th floor loft where extra bath is sometimes takes an extra 20 or 30 seconds or so for the water to turn hot but have only noticed it on that level where we don’t use it often. Love the fact that it doesn’t take up space in the garage.

I went to Home Deport last night to check out hybrid heat pump heater. I was surprised by its large size due to additional component being added for heat pump capability. No, I will stick with tankless water heater.

I was told that Rheem's electrical tankless water heater is priced way lower than the gas tankless water heater, is it the same case as in other brands?

I definitely will install a recirculating pump. Does anyone have experience with a tankless water heater with recirculating feature?

May I have your inputs on the quote I received for installing tankless gas water heater?

$2500.00 includes labor and material for a largest sized Navien tankless waterheater with recirculate pump, descaler, service valves and supplies needed for installation for water and exhaust.

Also, additional $575 for a re-circulation water line running over to the furthest fixture for the circulation of the hot water. The quotes are from a reputable plumbing company.

What is the "Descaler"?

It is a system removes scales in the tankless water heater to improve efficiency. I was told that some tankless water-heater makers would void warranty due to heavy scales in the unit. Google "descale tankless water-heater" for more information.

recently took out a short & fat 48 gallon electric hwh from under the stairs at a small guesthouse and replaced with a gas Rennai tankless water heater (propane). There was just not enough hot water for an old clawfoot tub. A guest said the tub material was so heavy & cold, by the time the bath & tub were finally warm the hot water would run out, they could not stay in and top off the tub periodically for a long bath. We already had a propane tank in place for a fireplace & cooktop, not a big deal to add the Rennai under the stair, vented through the wall. The plumber did all the work in a few hours, including cutting up the old tank into pieces to get it out.

Something I did not plan on was needing an electrician - it needs a 110v electric outlet for the control panel, the old hwh was 220v hardwired and that power supply cannot be used. For now it is plugged into an extension cord run to an outlet near the stair, but eventually I will have an electrician provide an outlet next to the tankless unit.

I know how to flush a tankless water heater - the google search isn't helpful.

The question is, in the context of this quote, what is the descaler?

Here's why I ask: If you have hard water you need a water softener.

"Descalers" are almost always bogus. Certainly anything with magnets and current and such are completely bogus.

From this thread I leaned not having sufficient capacity is one of the causes of complaints of using tankless water-heater. I guess the plumber heard it, it is why he selects the largest capacity. We do have both gas and electricity available, as well as contractors to handle issues on either energy source.

Wonderdog, Good point, I suspect the so called 'Descale' on the quote refers to a water softener system, as it was part of the conversation when we discussed installing tankless....I will confirm it.

From one of your previous postings and based on what I have been reading, I think you are correct that installing Tankless Water-heater is not as economical advantageous as I originally thought...unless I have missed some crucial, cost savings aspects using the system short term and long term wise.

You asked what we thought of the quote: The quote includes a "descaler" . I have no solid information on what that is... but I suspect it's a completely bogus piece of equipment. It's not a water softener. If you have hard water do yourself a favor and skip the "descaler" and buy a water softener.

Don't bother with any tankless unit that is significantly less than 200k btu input (they are usually 198-199k)

I installed tankless units in my last two houses. I've run the numbers backwards and forwards. They will save $80-100 a year in operating costs.

If you hire someone to clean them, particularly if you have hard water and no softener, and do that every 12-24 months, it will eat up all of your savings.
If you clean it yourself, esp if you have soft water so you are cleaning it every 24-36 months, it's a minor deal.

Don't buy a tankless only because it will save you money. It's difficult to recoup the install costs in a reasonable amount of time. Do buy a tankless if you want to save space, want continuous hot water and also appreciate saving $100 a year.

The most economical to install and operate is a hybrid tank heater. The payback on that is good, there are big rebates and you get cooling / dehumidification.

Could "descaler" be a reference to bypass valves for connecting a pump to run a manual flush procedure through the unit? My tankless doesn't have bypass valves so I have to disconnect the input and output lines to connect a pump for descaling/flushing.

dadoes,

While waiting for the plumber to get back with me about the "descaler" on the quote list.... may I ask how difficult to "descaling" with and without a bypass valves?

Wonderdog, I brushed off your suggestion of installing a hybrid tank heater when I saw one in a Home Depot store. May be I should revisit it.

May be I am back to square one.... I need a water-heater NOW, I don't mind to have a water softner as water here is hard, there are both electricity and gas available on the property, we have a small family and have never been running out of hot water....what hot water heater is best in term of cost efficiency, easy maintenance and longevity?

The term for the valves to which you connect the flush hoses are "service valves" which were mentioned separately in the quote. You don't ever want to install the heater without service valves. I feel certain the "descaler" is a bogus piece of equipment.

If you have hard water, a water softener will be very helpful for either type of heater. It also helps everything else stay clean and work better also. You can get a good water softener with a Fleck control valve for about $600 on Amazon.

Either type of heater will be fine. The tankless will last longer and give you continuous hot water, the hybrid will be cheaper to install and provide some cooling.

.

Thank you again Wonderdog for the inputs. .

Here is the response regarding Descaler "

The descaler is a cartridge that the water goes through prior to entering the water heater with an additive that helps to keep the water heater clean".

Sounds like I need to find out the cost and how often the cartridge should be replaced. So much to learn....Now I have new realization of "initial cost for tankless water heater is high".

I put a Rennai condensing gas unit in my son's house. With multiple roommates taking showers (I hope) it's working out great. It's nearly silent in operation.

The only pro I see for a tank heater is that it provides 40-50 gallons of stored water always on hand in the event of a disaster that stops the supply of water for any reason. OTOH, I've got my backpacking filter that would keep us going using river water for several weeks in the event of loss of a water supply.

HU-552153687

How hard is your water? If you have hard water install a water softener. It really will make a big difference for any water heater - as well as everywhere else.

We have very hard water here, I have already decided to install a water softener.

So skip the descaler, install either water heater and a water softener. There are trade-offs to both types that we've talked about already and either one will do a fine job.

There are great deals on Fleck based water softeners on Amazon - about $600. You do need to know the hardness level of your water and such before you order though.

Wonderdog, thank you again, I will check it out.

I have decided to get a gas tankless waterheater with a water softener. Am I spending more than getting a huge traditional tank waterheater, and it may take forever to reach the break even point for my investment? the answer is YES. But to me it is worthwhile to have an efficient system with correct set up.