Tankless vs Tank water heater. Whats will last longer? I already have a high powered solar water heater.

Page 1 of 2  
Does anyone have any knowledge about what is better, Tankless or Tank water heater?
Whats will last longer?
Middle of the line Tankless water heater has 5 year parts and 1 labor warranty cost about $1000. http://www.homedepot.com/Plumbing-Water-Heaters-Tankless/h_d1/N-5yc1vZbqjiZ1z109sr/R-202176600/h_d2/ProductDisplay?langId=-1&storeId051&catalogId053
50 gal Tank water heater has 12 years parts and labor and cost $640. http://www.homedepot.com/Plumbing-Water-Heaters-Residential/h_d1/N-5yc1vZbqowZ1z109srZ1z11t6dZ1z11uzjZ1z11l1u/R-100659227/h_d2/ProductDisplay?langId=-1&storeId051&catalogId053
I am replacing a 50 gal tank water heater.
I already have solar panel that are rated to heat the water by 60'F and then store it in a 50 gallon tank. This tank(solar heated water) is then connected to the gas tank water heater.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Why does tank water heater have 2times+ longer warranty than the tankless water heater?
Will the tankless gas heaters be worth it in terms of save money because off long term efficiency when I already have a solar water heater?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 23 Aug 2011 22:25:41 -0700 (PDT), rishi khanna

You just answered your question by being intelligent enough to ask it. The tank has a longer warranty because it will last longer - and your solar water heater will increase the efficiency of the tank heater
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@snyder.on.ca wrote:

More to the point.
The tankless has a crazy amount of BTU capacity. It has to, because it doesn't have much internal water capacity so it doesn't have much time to heat incoming water before it leaves the unit on it's way to your shower. You often need to supply a larger gas pipe to the unit - larger than even your furnace needs.
Combine that with all sorts of electronic burner and combustion controls and sensors, ignitors, computer controller, etc, and you've got a pile of electronics and wires that have $$$ written all over them.
I don't know why anyone would want a friggin blast furnace in their home just to heat water, when a conventional tank is so cheap and reliable. Anyone who can't afford a few hundred bucks to buy one instead of paying $300 a year to rent it is crazy.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The only real advantage to tankless is they take up less space. They are slightly more energy efficient but not enough to ever pay for themselves.
FWIW, last spring I replaced my natural gas water heater with another tank model.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Tankless also offer an unlimited quantity of hot water. You can't run out as you can with a tank type. That can be a factor for some applications.
I'd also check into what gas line capacity the tankless requires. Whole house ones typically need a larger line run, which could cost as much or more than the unit. However, in this case with a solar pre-heater, the tankless could probably be smaller, so a smaller gas line, ie the existing one, might suffice.
As for the warranty, the tankless has a 12 year warranty of the heat exchanger, 5 years on parts, 1 on labor. The tank type has a 12 year warranty on the tank and parts and 1 year on labor. So the main difference is that the tank type has coverage of parts other than the tank for years 6 through 12.
For actual longevity you might check Consumer Reports and see what data they have.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

i replaced my water heater last summer.
upgraded from a 50 gallon 75,000 BTU model to a 75 gallon 75,000 BTU tank.
buy a higher BTU model for essentially endless hot water. hgher BTU has shorter warranties but produces far more capacity..
theres lots of tankless downsides will post them tonight
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

As did I. 18 years of service from a $400 tank - $600 to replace - good for another 18???
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
rishi khanna wrote:

Facts:
1) Natural gas prices have been very low the past few years, and there's no indication that's going to change in the next few years. Anything you spend to reduce natural gas usage will have a proportionately small return on investment given low gas prices.
2) Conventional hot-water tanks are pretty efficient from a standing-loss standpoint, and what little heat they do radiate can be reduced by a relatively cheap external insulation blanket. On the other hand, the radiant heat loss from the tank is captured inside your house, the advantage of which is proportional to your northern geographic location (or as a function of altitude).
3) heat loss from a conventional tank flue is minimal if you have a power-vented system (when the fan isin't turning, it's acting like a baffle preventing air flow through the flue). I suppose a power-operated shutter could be added to completely close the flue and prevent heat loss when the burner is not on.
4) efficiency of heat transfer is inversely proportional to the heat gradient. The burner of an on-demand heater needs to put out 10's of thousands, even 100+ thousand BTU in order to heat incoming water during the water's short residency time inside the heater for the water to reach conventional hot-water temperature (typically 140 to 160 f). The more north you are, the colder your incoming water supply will be, and the more capacity (in BTU) the burners will need to be to bring the water up to the desired temperature. Exhaust heat loss from these units is significant while they are operating, and during their off-cycle as they cool down they can't dump much heat energy into the water because there isin't much water stored in the unit.
Conversely, the burner of a conventional water tank is capable of much less BTU heating, and the heat from the burner has more time to come into contact with the internal tank surface and transfer it's heat into the water. The exhaust gas temperature in the flue of a conventional heater can be so cool as to require a small electric blower to properly exhaust the gas out the flue. This is an indication that most of the combustion heat is being transfered into the water and not being exhausted out the chimney.
In other words, perhaps 50% of the combustion heat of an on-demand heater is actually being transfered to the incoming cold water and the other 50% is being lost in the exhaust, while 80% of the combustion heat is absorbed by the water in a conventional tank. The difference is that an on-demand heater is on perhaps 30 to 90 minutes per day, while a conventional tank might be on for 4 hours a day. But remember that when a conventional tank is on, it's burners are using a much smaller amount of gas compared to the on-demand heater.
5) the efficient use of an on-demand heater is challenged by short hot-water usage events. In most houses, the hot water lines are minimally insulated and thus the water in them quickly drops to room temperature. Anyone turning on a hot-water tap in an upstairs bathroom will notice it take 10 to 30 seconds to actually get hot water. It doesn't matter what type of heater you have (assuming the heater is in the basement). A short hot-water use event (say, washing your hands) will end up dumping a lot of waste heat out the exhaust when an on-demand heater is signalled to turn on and then soon after turned off to heat the water for that short-use event.
6) because of the very high heating capability (BTU capacity) of on-demand heaters, the extreme thermal cycling of their internal components will age the unit much faster than a conventional water heater, and they do or will require more maintainence and repair vs a conventional water heater (they have control devices, electronics, etc, that are not present in conventional heaters, and as we all know - electronics and HVAC equipment really don't tend to co-exist very well for the long term).
7) on-demand heaters have electrical or electronic controls that require a source of AC current. Thus they will not function during a power failure. Anyone living in a northern climate that is subject to sporadic winter power failures will not appreciate the lack of hot water during extended outages.
Conclusion:
No home owner that has a working conventional gas water heater will ever live long enough to recoup the savings from replacing his existing working heater with an on-demand unit - and it's not a given that there will actually be any measureable savings in gas use.
What has been observed is that the behavior of occupants change in terms of how they use hot water when a conventional heater is replaced with an on-demand heater, and that change usually results in less hot water use (shorter showers, changes in shower heads, installation of low-flush toilets, etc, insulating hot-water supply lines inside the house) so it's not always clear where the savings come from and why.
Replacing an old / leaking conventional water heater is very easy for most novice home owners / handymen, and at a cost of only a few hundred dollars, the cost/reward ratio is still heavily in favor of replacing a old conventional water heater with a new conventional unit.
You will get more bang-for-the-buck by
1) putting an insulating blanket around your existing or new conventional water heater
2) insulating as much of the hot water supply lines inside your house as you can reach
3) use a low-flow shower head
On-demand water heaters are basically a crock of shit designed to give plumbing and HVAC companies a very lucrative new revenue stream.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Your post was one of the most comprehensive and accurate summaries I've ever read on tankless heaters. Well done. While I wouldn't call them a crock, I would agree that there are only a few scenarios where they make sense.
If anyone is interested in more detail, Dr. William Hoover, former engineer for State Water Heater, wrote a paper on the topic called "What's the Big Deal About Tankless Water Heaters?". You can find it all around the net, but here's one link: http://www.cceci.com/Tankless_WhitePaper.pdf
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Except for the part about low-flush toilets reducing hot water usage... I've never flushed with hot water. The only people I know of who might flush with hot water are the ultra-eccentric, ultra-rich, and they really don't give a damn about saving energy.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@rochester.rr.com wrote:

Some of the measurements done on homes that have replaced conventional hot-water heaters with on-demand (tankless) heaters have also measured the changes in total water usage. The theory being that some water savings can be attributed to placing on-demand heaters closer to sinks and kitchens where you won't waste as much water waiting for hot water to come out of the fawcet.
Those measurements of water savings can be confounded by other changes performed at the same time, such as replacing conventional toilets with low-flush versions (which of course has nothing to do with hot water usage or the type of water heater).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

One would think that those that did the study would have kept other things constant. Seems mighty strange that installing a tankless would drive people to replace toilets. You have a link to that study?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@optonline.net wrote:

It's the mindset that's driving them.
They also bought Chevrolet Volts and eat free-range eggs (they're also vegetarians but DO eat egss because they believe in a woman's right to choose).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

True if it's a powered vent model. If it's not, a lot of the heat loss is up the flue when the unit is off.

It's not just radiant, it's all the heat that is captured. And in most cases, it's captured not in the living space, but goes to waste in an unheated basement or garage. And if the water heater is in the living space, then while it helps in winter, it also increases the cooling cost in summer.

The above is so totally wrong, it's laughable.. If that were true, tankless would be far less efficient that tank type. In fact, it's the other way around.
http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/water-heaters/tankless-water-heaters/overview/tankless-water-heaters-ov.htm
"Gas tankless water heaters, which use high-powered burners to quickly heat water as it runs through a heat exchanger, were 22 percent more energy efficient on average than the gas-fired storage-tank models in our tests. That translates into a savings of around $70 to $80 per year, based on 2008 national energy costs."
Who should we believe? You or folks who have done actual tests?

More nonsense.

It's not clear to me that they are more complicated than a direct vent high efficiency tank type.

So you say. Where is Ransley when we need him?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
T4-
Thanks for taking the time to reply to HG's items (4) & (5).....saved me having to.
His post started out ok by veered of in the middle... :(
I was originally enamored with tankless but the high tankless unit costs & the fact that my tank style water heaters last 20+ years kinda made it a no brainer. In the mild SoCal climate the tank pilot keeps the water hot..... I more or less have an "on demand" water heater anyway, main burner only fires with usage and I never run out.
Tankless CAN make sense but its all about usage and objectives...... endless hot water to fill a large jacuzzi tub >>>>> good endless hot water for a house full of teenagers >>>>> maybe not so good :)
cheers Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

One of the major considerations when thinking about going to tankless is energy supply. They will require a large electrical feed, or some type of gas. If that is not present, then the cost of the run (particularly for electric) can be substantial. Easy for new construction, not so easy for a retrofit, unless you are lucky, and are close to a source.
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Steve B wrote:

Anyone that has (or is thinking about using) electric water heater is crazy.
Electricity has been costly way to heat anything for most of this past decade compared to gas.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 8/24/2011 3:05 PM, Home Guy wrote:

gas may not be available in that area.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

DON'T BEAM ME UP, SCOTTY!
There IS intelligent life here!
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.