Water heater - conventional vs tankless - pros and cons

[garya505]

It looks like I may need a new water heater in the near future, so I have to decide between a conventional storage type or tankless.

I'm looking for pros and cons. Obviously the tankless is going to cost more. My HVAC guy says the tankless will cost 3X what the conventional would.

[hewitt]

tankless water heaters provide instant hot water,temperature of water can be adjusted as desire therfore when showering no need for turning on cold water.Unlike convential heaters it doesnot use electricity to keep water hot when not in use.Check out Rinnali tankless water heaters

[BaldLoonie]

With a conventional tank, once you buy it you rarely put any money into it for it's 10-20 year life.

The tankless will need routine maintenance, how often depends upon water quality. Could be annually. Add that cost to the annual savings, there might not be any. Look inside one? Lots of expensive controls, boards, blowers, gas valves, sensors. Pay for 1 repair out of warranty and you could have bought a couple of tanks :D

[garya505]

I'm seeing some stuff about the tankless, like the payback is 20+ years. :eek2:

[motoguy128]

Payback is pretty long. I put one in just to avoid having to reline my chimney which I'm not sure was even possible since it has 3 partitions/sections and tapers 1/2 way up.

I then invested a little extra for comfort and went with a unit that has a 1/2 gallon buffer tank and circulation pump, then ran a circulation loop so I have instant hot water.

Service life of a tankless if 20-25 years. But as mentioned routine maintenance is required. Hot water is endless and you have very high capacities.

Vents and gas piping MUST be size correctly.

Very little to break on a conventional tank. A tankless is like a modulating high efficiency furnace... but has a few more flow sensors making it even more complex.

Tankess is smaller, and can be mounted even in small closets. Combustion is sealed.

NO standby losses on a tankless. Tankless units need electricity. SO no power = no hot water.

[freonrick]

the problem with tankless is if you never run out of hot water you will never get your kids or wife out of the shower.

[carmon]

I personally do not like tank less heaters.... they cause head aches

[NY2GA01]

tankless water heaters provide instant hot water,temperature of water can be adjusted as desire therfore when showering no need for turning on cold water.Unlike convential heaters it doesnot use electricity to keep water hot when not in use. Check out Rinnali tankless water heaters

That is news to me.

No tankless water heaters that I know of are "instant hot", they are continuous hot water supply. It takes some time for the water to hit the faucet, unless it has a loop, but then it takes a few seconds for it to hit it, but once it does, it never runs out.

That is also the first time I heard of, no need for cold water adjustment with a tankless.

I agree with the Rinnai statment. That is the way I would go if I was to install one.

I would say the tankless are good option for vacation homes, where the water use is low. Other than that, I am not sold on them just yet.

[Joehvac25]

Waste of money, They take a long time to pay back. Think about it if you spend even 200 a year on natural gas and you save 30 percent of that maybe? $60 a year. If you want more hot water put a mixing valve on standard and turn temp up. Thats my opinion, there are some situations that they might benefit though. I'm sure others will have different opinions.

[HVAC/Stud]

I love them, I install Rinnai. They have a condensing unit, 95% efficent.

I have one in my house, save $30 a month and NG didn't go up hardly any.

I would not put in a elect or propane tankless.

They are the furture, just like mini-splits.

I set mine to 98 degrees prior to shower, and don't have to heat the water, then add cold water, saves energy. When done I turn it up to 120 for wife and dishwasher.

Go tankless, you will love it.

STUD

[Joehvac25]

I have a Takagi 82%. I like mine also, I think for someone who can't install themselves it's going to be pricey. I doubt I save much, I just got a good deal on it.

[hewitt]

U can set the temp of the hot water coming out of showers;@therefore no cold water would have to be used when taking a shower

[Joehvac25]

It all comes down to will it pay! I like condensing boilers because you save money but when a 500 dollar part goes bad there went your savings. If I was paying full price my 40 gal nat wtr heater and my 80% boiler (that I haven't even looked at in 3 years) would be fine with me lol.

[motoguy128]

It all comes down to will it pay! I like condensing boilers because you save money but when a 500 dollar part goes bad there went your savings. If I was paying full price my 40 gal nat wtr heater and my 80% boiler (that I haven't even looked at in 3 years) would be fine with me lol.

Payback can be relative. If you need direct vent, because of physical location, complicated flue relining, as well as trying to seal your house and eliminate all natural draft appliances, the price comparison isn't against a $$$ basic tank heater, it's against a $$$$ direct vent heater or a Vertex. I know my Navien was cheaper than the Vertex. A basic direct vent is still a single pipe, as is hte cheaper Vertex. Compared a tankless to the larger Vertex and it's a different equation.

It just depends on what yoru need are.

Add in the cost of a cirulation pump and small storage tank and controls if you want recirculation, and the "A" model Navien for example, looks like a pretty good bargin. SO now comfort and utility is added ot the equation.

Not everything needs ot have a stright payback. You cna get a 2 stage Carrier Comfort 2 stage or even jsut single stage series and Performance series furnace for about 10-20% less than the same Infinity system with identical efficiency ratings. But it doesn't have Infinity control.

[garya505]

Payback can be relative. If you need direct vent, because of physical location, complicated flue relining, as well as trying to seal your house and eliminate all natural draft appliances, the price comparison isn't against a $$$ basic tank heater, it's against a $$$$ direct vent heater or a Vertex. I know my Navien was cheaper than the Vertex. A basic direct vent is still a single pipe, as is hte cheaper Vertex. Compared a tankless to the larger Vertex and it's a different equation.

It just depends on what yoru need are.

Add in the cost of a cirulation pump and small storage tank and controls if you want recirculation, and the "A" model Navien for example, looks like a pretty good bargin. SO now comfort and utility is added ot the equation.

Not everything needs ot have a stright payback. You cna get a 2 stage Carrier Comfort 2 stage or even jsut single stage series and Performance series furnace for about 10-20% less than the same Infinity system with identical efficiency ratings. But it doesn't have Infinity control.

Can you elaborate on the venting issues? For example, in my case I have a conventional WH and a 80% furnace which both take their combustion air from inside the garage (the garage is vented allow outside air to come in). So, what would be the choices for tankless WH in this situation?

[CraziFuzzy]

I would never consider a tankless water heater as a money saver. It just isn't. Tankless water heaters, first and foremost, are a convenience item. The key part is the endless host water aspect (important if you live with a lot of women/girls).

[Cooked]

The G.E. GeoSpring looks attractive although I have no hands on with it.

[garya505]

The G.E. GeoSpring looks attractive although I have no hands on with it.

I saw that one too. I think it would be a serious contender if I was replacing an electric or propane WH.

[vstech]

That is news to me.

No tankless water heaters that I know of are "instant hot", they are continuous hot water supply. It takes some time for the water to hit the faucet, unless it has a loop, but then it takes a few seconds for it to hit it, but once it does, it never runs out.

That is also the first time I heard of, no need for cold water adjustment with a tankless.

I agree with the Rinnai statment. That is the way I would go if I was to install one.

I would say the tankless are good option for vacation homes, where the water use is low. Other than that, I am not sold on them just yet.

the BIGGEST advantage to a tankless aside from the neverending supply of heated water is you can set the temp for what your shower temp is. you don't heat the water to 130 then cool it to 98/105, you just set it to 105, and turn on ONLY the hot water.
obviously it takes less fuel to heat the water to 105 than 120/30/40 what have you... and then mix it down to a comfortable temp at the shower.

[motoguy128]

you just set it to 105, and turn on ONLY the hot water.
obviously it takes less fuel to heat the water to 105 than 120/30/40 what have you... and then mix it down to a comfortable temp at the shower.

That's only partially true. Higher temps consume more fuel not because you heat the water higher in itself. It becaus ehigher tmperatures result is both 1) lower combution efficeincy and 2) higher storage and distribution losses. storage tank heater should be kept higher ot avoid leigonella issues.

3 reasons ot set a tankless at a lower:

1) Higher combustion efficiency at a lower temp rise.
2) Eliminates scalding risk (imrpotant if you have kids and don't want to fuss with the cost and hassle of a antiscald valve)
3) Higher flow rates from using lower water temps can help reduce scaling in the heat exchanger.

Also, keep in mind most newer dishwashers have built-in heat strips ot raise the water temp. So that's not a reason to run high temps for hte other 95% of water uses.

I find 110-115F to be an ideal compromise. I have mine set to 112F. I temper it just a little for showers, I believe my wife leaves it pretty clsoe ot 112. :)

I also find that it's easer ot control the water temp when you're starting at 112F and the you get hot water sooner when you are drawing 2 GPM through a pipe than .5 GPM and you have lower losses in the pipes.

[glennac]

Tankless water heaters will never pay for themselves. Get a Marathon electric hot water heater. They will last indefinitly since they can not rust. Only have to replace the heating elements when they wear out and the cathode. Check these out. They cost a little over twice as much but install price is the same. And should shouldn't ever have to replace it. Technologically advanced design is clearly differentiated from short lived steel water heaters It's the most durable water heater made, with a warranty to match. Thank you very much.

http://www.marathonheaters.com/

[garya505]

Tankless water heaters will never pay for themselves. Get a Marathon electric hot water heater. They will last indefinitly since they can not rust. Only have to replace the heating elements when they wear out and the cathode. Check these out. They cost a little over twice as much but install price is the same. And should shouldn't ever have to replace it. Technologically advanced design is clearly differentiated from short lived steel water heaters It's the most durable water heater made, with a warranty to match. Thank you very much.

http://www.marathonheaters.com/

How do they do in places that have a lot of minerals in the water? Around here, water heaters only last about 10 years because of build-up inside the tank.

[vstech]

if manufacturers instructions are followed, the build up is removed on the annual flushing they require, and the anode gets changed on schedule to prevent the tank from corroding...

[Cooked]

Tankless water heaters will never pay for themselves. Get a Marathon electric hot water heater..........I think Gary iss looking for a natural gas heater......They will last indefinitly since they can not rust. Only have to replace the heating elements when they wear out and the cathode....???........

These tanks don't use an anode rod.

From the General Pacific (reseller) website, http://www.gpconservation.com/

"All plastic tank eliminated the need for an anode rod preventing potential odor problems."

And the "bowl" shaped bottom is supposed to generate a swirling effect to prevent sediment buildup and become self cleaning when drained.

But I think you're on to something Glen. I really like the idea of a poly tank. Glass lined steel tanks have served us well for generations but they have their issues. These poly tanks seem well worth the money to me especially if your plan on staying in your home for a long time

[Joehvac25]

Can you elaborate on the venting issues? For example, in my case I have a conventional WH and a 80% furnace which both take their combustion air from inside the garage (the garage is vented allow outside air to come in). So, what would be the choices for tankless WH in this situation?

Anything with intake and exhaust pipes, they draw outside air for combustion. Most any tankless and some storage type have outside intake air inlet.

In a cold climate that is one more thing to consider like mentioned, typical draft vent takes inside air and also pulls heat out when not in use.

Like I said I have a Takagi and like it for lots of reasons. If you think you will go on vacation with the energy savings you might want to rethink. So there are a thousand variables and every situation calls for its own solution.

[jpsmith1cm]

Joehvac25


Please check your PMs.

[pacnw]

To those that say setting your temp lower is an advantage, many homes do not have individual hot and cold valves so you have the mixing of hot and cold anyway.
Also, your dishwasher manual will ask for 120° water. Many have their own heater, but then did you add the cost into your ROI calculation. Same may be true for wash machine.
As for standby loss, has anyone actually calculated it, or are you going off the mfr statements? Realize that the stadby is not from new cold water to your setting, but from water that has fallen in temp back to your setting. Is that really a large useage.

[CraziFuzzy]

To those that say setting your temp lower is an advantage, many homes do not have individual hot and cold valves so you have the mixing of hot and cold anyway.The comment was regarding the amount of water that is mixed to get your desired temp, not really the method at which you control the temperature. By running the tankless at a temperature closer to the temp you want at final use, you can draw more water through the hot water piping, which will reduce potential scaling of the heat exchanger, by increased flowrate through it.

As for your other comments on ROI and such, as I had mentioned earlier, there isn't really any ROI on tankless heaters. it is all about convenience, not efficiency. The side effect most don't realize initially, is that you are likely to use a LOT more water with a tankless water heater than you would a tank one. Not only because you take longer showers, but also you end up running more water down the drain before getting the hot water, because the initial flush of cold water down the pipes before the water heater turns on.

[pacnw]

The comment was regarding the amount of water that is mixed to get your desired temp, not really the method at which you control the temperature. By running the tankless at a temperature closer to the temp you want at final use, you can draw more water through the hot water piping, which will reduce potential scaling of the heat exchanger, by increased flowrate through it.

As for your other comments on ROI and such, as I had mentioned earlier, there isn't really any ROI on tankless heaters. it is all about convenience, not efficiency. The side effect most don't realize initially, is that you are likely to use a LOT more water with a tankless water heater than you would a tank one. Not only because you take longer showers, but also you end up running more water down the drain before getting the hot water, because the initial flush of cold water down the pipes before the water heater turns on.

:cheers:

[catmanacman]

if manufacturers instructions are followed, the build up is removed on the annual flushing they require, and the anode gets changed on schedule to prevent the tank from corroding...

And there go the savings

[catmanacman]

Tankless water heater do have advantages for example if you have a big whirlpool tub or a big family ,or your doing a remodel and dont have space for a tank as for them saving money i dont see it by the time you pay for the install and mainteance and if you have hard water you need a softner it will be a long payback .

[precision hvac]

I see lots of people have drunk the tankless Kool-aid.

We install Rheem tankless & Rheem storage water heaters.
My own home has a 50 gallon water heater. You won't ever find a tankless in my house.

Special venting, 3/4" gas runs to the meter, 120v power, PITA to install a circ system on, yearly flushing (that no one ever does) & the cost. Usually, I could install 3 tank water heaters for the price of one of these tankless units installed.
Oh- yea, they save money? 199,000 BTU instantanous on demand vs 30,000 btu w/ an R19 tank. Don't believe it for a minute.

Oh- and wait till it fails on Christmas eve- you have your whole family over for the holidays & no hot water- and the tech has to order parts!

Tank water heater? Lets see. Thermocouple, Unitrol gas valve & relief valve. Got that on the truck.

[lentz]

Tank-Less is good if you do not have to put it to far away from the use. The venting can be really high in cost. Some do have plastic piping for vents but some reports have just came out saying do not use plastic pipe for vents. No matter what the manufactor says.The joints come apart from fumes and heat. Some units do have recir. pumps so you have hot water as soo as you turn on the faucet. You will most likely never get you money back in savings. Some times it takes a week to get the parts if you have a problem and your plumber does not know how to repair it. I do not recommend
them but if that is what you want I will install it for you. The sales have fallen off bad. There is a holla-hoop coming every six months and every one has to have one. Don't turn on the washing machine or dish washer while you are in the shower.

[motoguy128]

Don't turn on the washing machine or dish washer while you are in the shower.

Why? I've turned on ever faucet in my house with the unit set to 140F and with about 50F incoming water, it kept up just fine. It's just a matter of having enough BTU's. But... I have the 1/2 gallon buffer tank on mine. I think it makes a world of difference.

Again, for me it was comparing a Navien to a Vertex or a regular direct vent unit. IT was cheaper than a 2 pipe Vertex. So my payback includes relining a chimney that I couldn't reline.

But like others, I don't recommend them for the average home owner in a normal situation. IF I wasn't comfortable troubleshooting it myself and doing hte basic maintenance, I wouldn't have gotten one.

[hcong]

I like tankless. You have to pay for a bigger gas line and more upfront but you only heat water when you need it.

[CraziFuzzy]

Don't get me wrong, I'm not saying I'm against tankless heaters. Personally, I love mine, and can't imagine going back unless it was a VERY expensive and very large tank - But I never fooled myself into thinking I'd be saving money with the tankless...

Another great side effect of the tankless. It being wall hung saves quite a bit of space in my garage where the old tank heater was - perfect for the brand new softener.

[duckman06]

Waste of money, They take a long time to pay back. Think about it if you spend even 200 a year on natural gas and you save 30 percent of that maybe? $60 a year. If you want more hot water put a mixing valve on standard and turn temp up. Thats my opinion, there are some situations that they might benefit though. I'm sure others will have different opinions.

My company is also a plumbing company an we install a lot of tankless water heaters. With that said the payback does take quiet a while! Example that I can use installing a 20 seer a/c system, the payback is not there due to the up front cost.

It boils down to comfort in both regards regardless if a 20 seer system or tankless water heater both have long payback times. Customers who want this products need to not look at the payback put what the units can do for them inregards to comfort. Neither will pay for themselves in a timely fashion!

I personally do not have a tankless water heater for the simple reason I don't have natural gas to my home and there is no way that I would install electric tankless to many problems. I have a 16 seer HVAC system not a 20
Seer for the payback as this is not my last home.

I do have a variable speed air handler even though I could have gotten the same eff. Out of the system with single speed fan why comfort level in my home. Same goes for tankless if you want endless hot water once it reaches the outlet then tankless is the way to go.

A tankless will save you money but again it will be along
Payback compared to tank heater due to cost. Out of all the tankless water heater that we have installed, I have never had a unhappy customer same as every 13-20 seer system we have installed. As long as done Propley and the customer understands the pros and cons and what it can do to help them in there homes water/eff. Them you have done your job...

[maxster]

tankless makes hot water 24/7 with 55F entering conventional:cheers: stores hot water for the first to use it ....after that 55F mixing with 130F stored water....note:gah: if you relocate the location of the HWH then to tankless to another the time to get hot water changes.....longer that hot water out there will add to wait time

[enb54]

Have a Rinnai tankless in our investment house, have two regular gas tanks in our own house, and had an indirect in our old house. Out of all those, would have to say the indirect gave the most consistent smiles on our faces, lowest maintenance (plastic liner) and in my own opinion is really the only way to go. Just another opinion on DHW heaters...

[garya505]

Have a Rinnai tankless in our investment house, have two regular gas tanks in our own house, and had an indirect in our old house. Out of all those, would have to say the indirect gave the most consistent smiles on our faces, lowest maintenance (plastic liner) and in my own opinion is really the only way to go. Just another opinion on DHW heaters...

What is an "indirect" water heater?

[CraziFuzzy]

I think he's talking about a tank with a coil in it, using another heat source to heat the tank (like from a comfort heating boiler). In which case, it's actually the boiler that is the real heat source.

[enb54]

I think he's talking about a tank with a coil in it, using another heat source to heat the tank (like from a comfort heating boiler). In which case, it's actually the boiler that is the real heat source.

Yes! Was fed by a boiler system and basically was terrific...

[CraziFuzzy]

Keep in mind MOST people don't even have a boiler...

[motoguy128]

Yes, that's called a indirect water heater. You can use a boiler or some use a combination of a boiler and solar or tankless combi with solar to heat the water.

Yes, it's still the best method for water heating because you can get very high BTU capacity and they come in fairly large sizes and can be cascaded as needed But they are not compact, usually very large, and efficiency depends on the heat source.

Hydronics in various forms are still hte best heat soruce overall. But the most expensive ot install, that's why boilers have become less common. Once forced air furnaces came on hte market, they dominated. Even heat (with proper ductwork) good efficiencies and a fracton of the installation cost and no cast iron radiators.

[enb54]

Yes, that's called a indirect water heater. You can use a boiler or some use a combination of a boiler and solar or tankless combi with solar to heat the water.

Yes, it's still the best method for water heating because you can get very high BTU capacity and they come in fairly large sizes and can be cascaded as needed But they are not compact, usually very large, and efficiency depends on the heat source.

Hydronics in various forms are still hte best heat soruce overall. But the most expensive ot install, that's why boilers have become less common. Once forced air furnaces came on hte market, they dominated. Even heat (with proper ductwork) good efficiencies and a fracton of the installation cost and no cast iron radiators.

Yes they are expensive to install, but if they are maintained properly, they seem to last forever. I currently have two 50K BTU forced air furnaces (93%) and two 40 gallon gas fired hot water heaters (e/w inducer fans), when they start giving trouble, will replace with one 100K or so boiler and indirect tank, with two air handlers, that will free up a lot of space in my furnace room. That indirect at my old house was 40 gallon Amtrol and it was impossible to run out of hot water, even with two teenagers...

Mind you, my current DHW setup uses one tank to preheat the other, and have never run out of hot water either... :)

[lentz]

That's only partially true. Higher temps consume more fuel not because you heat the water higher in itself. It becaus ehigher tmperatures result is both 1) lower combution efficeincy and 2) higher storage and distribution losses. storage tank heater should be kept higher ot avoid leigonella issues.

3 reasons ot set a tankless at a lower:

1) Higher combustion efficiency at a lower temp rise.
2) Eliminates scalding risk (imrpotant if you have kids and don't want to fuss with the cost and hassle of a antiscald valve)
3) Higher flow rates from using lower water temps can help reduce scaling in the heat exchanger.

Also, keep in mind most newer dishwashers have built-in heat strips ot raise the water temp. So that's not a reason to run high temps for hte other 95% of water uses.

I find 110-115F to be an ideal compromise. I have mine set to 112F. I temper it just a little for showers, I believe my wife leaves it pretty clsoe ot 112. :)

I also find that it's easer ot control the water temp when you're starting at 112F and the you get hot water sooner when you are drawing 2 GPM through a pipe than .5 GPM and you have lower losses in the pipes.



Just read an artical that setting our water heaters on tempertures less that 140 degrees could raise question about leigonella issues. Water standing in our pipes or storage tanks could cause a problem.

[CraziFuzzy]

We were discussing lowered tempus on a tankless, not a storage heater. Legoonella its only of concern in warm storage systems. In a tankless setup, the water isn't at a proliferation temp long enough to promote any significant bacterial growth.

[SolarMike]

The magic number is 120F (50C) and if the water is heated to 140 (60C) every 2-3 days for an hour, it won't form. It is only transferred by fine mist and is quite rare.

[SolarMike]

Yes, that's called a indirect water heater. You can use a boiler or some use a combination of a boiler and solar or tankless combi with solar to heat the water.

Yes, it's still the best method for water heating because you can get very high BTU capacity and they come in fairly large sizes and can be cascaded as needed But they are not compact, usually very large, and efficiency depends on the heat source.

Hydronics in various forms are still hte best heat soruce overall. But the most expensive ot install, that's why boilers have become less common. Once forced air furnaces came on hte market, they dominated. Even heat (with proper ductwork) good efficiencies and a fracton of the installation cost and no cast iron radiators.

HEEEYYY, I ripped out my forced air and put in some of those cast iron radiators. My clients love them, even heat, efficient and can work with radiant and solar.