I am considering a tank-less water heater, as of date I haven’t found any one that has one , to ask if they are appropriately sized for a standard family and household. Can any one give your option if you have been using one for sometime. And are the worth the cost in terms of savings payback, I currently rent one from the gas company.
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You RENT a tankless from the gas company?? If you are considering one for savings in a 'standard' household application, there isn't much savings to be had. Tankless primarily save the standby heat loss from a tank style heater ... which if in a conditioned or tempered space loses very little. Compared to hot water consumption by showers, etc. the standby loss is tiny. Now if you are needing to replace your hot water tank ... consider resizing to better match your reduced loads from better shower heads, dishwashers, etc.
Blanket claims of big savings with tankless and applying them everywhere is a lot of bunk. They cost a lot to install (bigger gas or electric service). There MAY be some savings in terms of combustion efficiency over a really old water heater, but you can do that w/ a new tank style heater too.
We had a tankless for 3 years and hated it. After replacing with a tank, I had NO increase in gas usage.
Biggest complaint was the inability to get low flows of hot water needed for such things as cooking or shaving. Heater continually shuts off.
One huge concern for those thinking about switching to tankless is the huge flue required. Some folks are, however, using the old furnace flue after converting their furnace to hi-eff with PVC vents.
"One huge concern for those thinking about switching to tankless is the huge flue required. "
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Depends on the tankless, but often the flue is smaller than a comparable tank hot water heater. I switched from a 3" roof vented flue to a 2" side wall vent when I switched to a tankless.
FWIW, we love it, would never go back. It's wonderful to have nearly instant hot water that does not run out. I don't miss the waiting for hot water, running out of hot water, and high energy consumption of a tank hot water heater at all.
A tankless, given the same location and piping size, can't deliver first hot water any faster than a tank WH.
In fact it will be a few seconds longer because unit has to sense water flow, fire the burner, and get the heat exchanger and first slug of water hot.
A tankless, given the same location and piping size, can't deliver first hot water any faster than a tank WH.
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I agree that both the tankless and tank have to move the same amount of cold water out of the pipes before they can provide hot water.
The tankless does take 15 to 20 seconds to fire up and supply hot water. However, the water in the tank heater is not all at the same temperature - it will be hotter closer to the burner, and in addition the water temperature will vary by 10 F or more, depending on the thermostat tolerance.
So the net effect is that they both provide water that is heated to a degree in roughly the same time. However, the tankless water is at full temperature while the tank heater water is lukewarm at best, until enough water is run out of the tank to get to the hot water.
So the net effect is that the tankless supplies full hot water in the time required to clear the cold water out of the pipes, while the tank heater supplies hot water cold water that becomes full hot water another 30 to 60 seconds later.
There is alot that goes into the dicussion of tankless vs tank, and its not all just about cost savings. I installed a noritz tankless n-132-m (the biggest one they make, its actually a commercial unit) in my house a few years ago. I had to run a dedicated 1" gas line. I use a lot of water at my house, and you can't kill this machine. 3 showers, a dishwasher, clothes washer, and a couple sinks can all run at the same time, no problem. That being said, if you demand is not very great, you might be better off with a tank heater. however, I don't think tankless are a great deal more to run, in fact, in my situation, my monthly bill has actually gone down, and my water heater dosn't run all day like it used to. Hope this helps, Adriel
>> and my water heater dosn't
>> and my water heater dosn't run all day like it used to.
What sizwe tanked heater did you replace?
I looked into to a gas tankless units, but bought another standard tank water heater. One thing that helped me make the choice was that even though we are on split utilities and Propane, if the electricity goes out, there is no hot water because of its electrical valves and circuit board requirements....
I presently have a 40 gallon natural gas heater.
it seems to keep up with the demand for hot water the household uses.
I have converted the furnace to H.E. and the tank heater
is vented to the chimney with a liner installed after the furnace conversion.
So before I go ahead and convert the heater to tank less
I was looking others comments about the performance of the tankless heaters.
You have a tank style that is working. A tankless will heat water as efficiently as a tank style in general. If you want or need to get rid of your old water heater, a new water heater will heat water as efficiently as a tankless. Savings is only in the elimination of the standby losses through ... which is normally very small ... and if you use hot water like a normal family/user, the savings end up being VERY small. Unless you got other reasons to go tankless, I wouldn't. The savings won't be large and your installed cost will be very high (relatively speaking).
When folks discuss energy savings for tankless HWH's, they invariably use the extreme example of a vacation home with 140 deg water sitting idle for months on end -- look folks, you can save up to 50% of your heating bill! Well ... c'mon now, anyone with a vacation home turns the HWH off when they leave.
Super sized jacuzzi's are about the only fixture that needs a tankless ... and if you regularly fill one of them, why would you even care about energy savings.
If you do have teens who love endless steamy showers, I should think running out of hot water is a God send.
Right on. Like many energy products I run into, they are often marketed as 'good for all applications' when in reality, their technology is VERY good ... applied to the right situations.
While many people may very well save a lot of money w/ the tankless over their old 60% efficient water heater, that doesn't make the argument for choosing the tankless over a tank style efficient replacement.
A salesman will likely over imply that standby losses on a tank are 'substantial' when in fact they generally are not.
The point being, we have to understand the basic technology and the limitations to be able to make informed decisions that are in our own best interests (not the salesman's).
Check out my post about the Navien tankless units they look pretty sweet!
We had a 40gal tanked model that just could not keep up with our needs. My wife and I always shower one after the other and, me going second, I would often get a tepid shower. Not anymore with the Rinnai tankless I installed.
Also another big thing that should not be overlooked is the space you save going to tankless. You basically create enough room for a closet by doing it.
I'm sure they do look sweet.
I'm sure they do look sweet. Don't get me wrong, I've nothing particular against tankless technology. For your situation, a tank style isn't any worse than a tankless. Just because 40 gal wasn't enough doesn't mean tank style is not a good thing ... just means you didn't have a big enough tank (or something was wrong w/ your tank).
One more aspect in this discussion is the matter of maintenance and service calls.
One or two service calls that might be required during the life of a TWH will quickly add hugely to their total cost.
I don't have data to indicate that TWH's do require more frequent servicing, but, wow! are they ever complex. I certainly would not feel qualified to tear into one, and I have doubts about many of the installers as well, because they don't generally have extensive experience with TWH's.
But maybe the parts are cheap? :)
If you do have teens who love endless steamy showers, I should think running out of hot water is a God send.
Boy you're right about that!
when I replaced the old electric water heater with a new, higher capacity one, I thought afterwards, "Now, why did I do that????? It'll just enable longer, more comfortable showers for the 4 (yes, 4!) teenagers in the house."
Just got the email for the FHB discussion on tankless waterheaters and had to put my two cents in.
A few years ago I read an atricle in one of the mechanical engr monthly mags about tests on gas tankless waterheaters. The bottom line was there is no or minimal savings. This was after I just installed an electric TWH. I had to run two 8 gage lines to it- replumbed (did this myself so it cost time and materials on my part. It is on the basement wall below the sink and only services a dishwasher, washing machine and sink. Mind you there is 3 foot of line and since I installed the unit I have to turn the sink on to prime the system and get hot water running (2 gal lost) and when the dishwasher recyles the reheater now has to bring the water up to temperture (excessive electricity lost). The washing machine hasn't seen hot water (20 ft away) in years.
I am head of an engineering dept and we joke about this rube goldberg setup (the twn waterheater). I know you can put in storage tanks etc - but why waste time and more money trying to make junk work.
Our old tank water heater failed on the third floor - my wife said no twh, and I agree. I checked for a marathon super insulated lifetime heater, but they are not in my area.
Other people in our office have purchased housed with twh - most have pulled them at the first chance.
BTW my unit is a national brand - so it is not a cheap knock off.
In my opinion the most elegant solution is the simplest - buy a super insulated lifetime heater.
boag, can you link that Mechanical Engring article about the farce of energy savings with tankless HWH's?
I bought a house with a huge jetted tub and tankless HWH. We had it for 3 summers so I was able to compare natural gas energy use with the tankless and then with a hi-eff tank I replaced it with. The energy use was basically identical. Do advertisers lie?
The jerk who installed the tankless for the prior owner connected the 7 in diam sheet metal flue to a 2in by 6in chimney flue! "Honey, why do I smell gas in the basement?"
There are several ways to get more hot water out of a tank-style HWH. When we had overnight guests, I would raise the temp to 140deg in the tank. If replacing the unit, up-sizing from 40 gal to 50 gal is easy. Also high recovery units are available with a 4 in diam flue.
Advertisers don't lie ...
Advertisers don't lie ... they just spin a web of truth that makes them look good. TWH will ELIMINATE your standby losses. True, but for many households, that is a pretty tiny number ... not noticeable on your energy bill.
You are absolutely right about capacity and temperature. Generally I recommend people turn down their temp until they run out of hot water during their normal routines, then turn it back up a bit. Having company? As you say, increase it to compensate for those few days.
TWH will ELIMINATE your standby losses. True, but for many households, that is a pretty tiny number
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Yes, in the range of 19% to 30% energy savings, according to studies and personal experience. If that's tiny in your book....
The exception is families that run hot water nearly continuously, because they aren't "paying" the standby loss. So, for a two-couple working family, where they draw water mostly for an hour or two in the morning and evening, they are likely to see that 30% savings. If it's a family of 12 running water constantly, probably not.
In another post, you mentioned the "apples and oranges" aspect of an older, less efficient tank heater compared to a tankless. Fair point, but a high efficiency tank hot water heater costs as much or more than a tankless. That was a deciding factor for me when I went with a tankless - the cost of a mid efficiency tank heater was more than the cost of the installed tankless.
One other consideration - others have mentioned the benefit of having a tank of water on site, but no one has mentioned the detriment. Tank hot water heaters leak, break, and cause flooding. Happens a lot. Generally avoidable with regular maintenance, inspection, and replacement, but most people don't do that.
I used a tankless gas water heater for the sole source of domestic hot water in my home for years. Are they appropriately sized for a standard family and household?Some are, some are not. They will save you energy (and be worth the cost) if you use hot water only a few time a day. We typically used hot water once a day - morning shower. A lot of "standing losses" were eliminated by not having a 50 gallon tank of 140 deg water giving up heat the the basement all day and all night. Another benefit is that it provided an endless supply of hot water. You will not run out. OTOH, I hated it and now use it as a small condensing boiler for an infoor garage heating system. IF you have any transients, a tankless will react very quickly, but you will still get hot and cold surges. If you have a large house or want to recirculate to keep the "wasted" water down (i.e. running the hot down the drain until it gets hot at the sink) you can't do that with a tankless. Personally, I hated it.
want to recirculate to keep the "wasted" water down (i.e. running the hot down the drain until it gets hot at the sink) you can't do that with a tankless
Why not? Can't you recirculate the hot line at the sink through the cold line?
Tim
Did you miss my question to you?
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Here in Pixburd, or as the locals now say "Sixburd," any heat "wasted" by the HWH in the winter time is not wasted, but only heats our basements. My tank heater is heavily insulated and kept at 115deg. I have "kids" who won't use exhaust fans, so this is my "punishment" to them.
Another issue seldom mentioned, especially for those with wells, whose water needs electricity to operate, a tank of hot water in the basement provides some added security when the power foes out. Tonight we are expecting ice storms.
Merry Christmas!
My tank heater is heavily insulated and kept at 115deg. I have "kids" who won't use exhaust fans, so this is my "punishment" to them.
You could also be punishing your family with little nasty microbes in the water heater at only 115 degrees.
Raise the temp to 125 or more. Add a thermal mixing valve (not just a globe/gate/ball valve) to get that desired lower max hot temp.
Add a humidity sensor to your exhaust fan circuit to automatically turn on the fan.
<>
Microbes!! Is that what I smell?
Well, if you'd change your
Well, if you'd change your underwear more often ...
Yes a lot of standing losses are eliminated w/ a tankless. In fact virtually all of the standing losses are eliminated ... but that is a very tiny amount of energy (relatively speaking). WE typically use hot water once a day ... A MORNING SHOWER. I suppose if you shower together. You don't use it to wash dishes or do the laundry? Non for cooking or washing your hands? Wow.
I get tired of hearing of the 'energy savings' had w/ tankless. If you replace an old tired water heater, yes, you will save energy ... but so will the replacement tank style heaters. You can actually and fairly easily calculate how much the standby losses are. I've done it and generally speaking, it ain't much ... assuming the tank is insulated of course. Even so during the cold months the standby loss isn't much wasted assuming the tank is inside the thermal envelope.
Not sure what you mean when you say you now use your old water heater as a small condensing boiler for your radiant floor.
Which word(s) are confusing you? If this tires you so much, why bother?
We actually DO shower together and do not wash dishes or clothes daily. I rarely use hot water, or tap water for cooking.
I should have stated that I use the tankless water heater as a modulating heat source for my garage radiant floor. Hot water goes through tubes in the slab, warms up the place real nice. Is it the radiant floor concept or the use of a tankless water heater to make hot water the confusing part?
I was just confirming that I heard you right, that's all. Your statement was a bit unusual, not confusing.
I'm making a general statement re: being tired of hearing about 'big savings' from TWH. GENERALLY there aren't 'big savings'. If you use so little hot water, a smaller tank style water heater would serve you fine. TWH are frequently sold as the answer to everything. Every technology has a time and place including TWH. I've recommended them on a number of occasions myself. But as big energy savers for the normal routine of domestic hot water use, they simply are not.
GENERALLY there aren't 'big
GENERALLY there aren't 'big savings'.
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You have said that several times in this thread, but that conflicts with personal experience and studies. Have you seen any studies or other testing that support your conclusion?
I'm just trying to reconcile the apparently contrary opinion with the documentation. Often in these cases there is a difference in the test cases that result in the different findings, but we would likely need to review the test report to identify these differences.
As I posted before, I had 3
As I posted before, I had 3 years with tankless and 3 years with a hi-eff tank unit in the same house. My data was for the 6 months when the furnace was off. My stove and dryer were both electric. I had controlled conditions and enough data to satisfy me. I was looking for that 50% savings they advertise. That's the number most people use when they decide to change to tankless.
My brother has a cottage on the lake. He NEEDS a tankless. But it wouldn't save him any money because, because like most smart folks, he turns the tank off when he is not there. And that's my point. Unless one leaves his tank on 140deg, and then never uses it, he may never save a penny.
In fact, he LOSES big time. Think about the expense of installing tankless -- higher initial expense, cost to enlarge the flue thru the roof, and the labor. If your payback is 5%, it might take 50 years to recover the expense. Not a good investment.
Then ... we have to discuss the endless aggravation of having the tank shut itself off when the flow is too low ... like when I'm shaving. Ahhh ... now I get it. Since I had to run the hot water in the tub while I was shaving, so that the unit would stay ON, that's why I never saved any money. All the savings went down the drain. Brilliant Watson!
Think about the expense of installing tankless -- higher initial expense, cost to enlarge the flue thru the roof, and the labor.
...
Since I had to run the hot water in the tub while I was shaving, so that the unit would stay ON, that's why I never saved any money.
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I'm not convinced the cost of installing a tankless IS higher than a high efficiency tank hot water heater. Though people talk a lot about needing a larger flue and larger gas lines, in many or most cases that is not required. In my case, I went from a 3" roof vented tank to a 2" wall vented tankless. All said and done, cost for the tankless installed was a little less than the high efficiency tank would have cost - and I saved a roof penetration. Of course, being a typical Pittsburgh house, it's slate roof and the repair cost is extravagant, so I didn't really remove the old flue.
Usage patterns will obviously affect energy savings. If you are running the bath water while shaving, that would impact efficiency. For me, with the tank heater in the winter I would need to run the hot water about 80 seconds to get hot water at the top floor bathroom. With the tankless, it's more in the range of 10 seconds. No need to run the bathtub, no drop in temperature for the hot water.
Maybe you could try filling the bathroom sink instead of shaving with the water running?
Some changes in usage may be helpful with a tankless, since most people are used to tank heaters. It's that way with any change in technology or equipment.
If I ever have to go back to a tank hot water heater, I will need to make similar adjustments. I'll miss the nearly instant unlimited hot water, but I guess I would eventually get used to using cold water to wash hands and shave again.
Ultimately, it's personal preference, but I wouldn't choose to go back to a tank hot water heater.
OK ... I checked my own calcs and recalculated some stuff.
A 'typical' family of four might use from 50-60+ gallons of hot water/day according to a couple of sources I googled.
Based on this, your annual hot water bill would be on the order of $180-200/yr electric and $130-160 gas at 7 cents/kwh and $1.20/therm ... of that, the standby loss for e.g. a 50 gal tank would be about $25 and $20 respectively for the standby loss assuming reasonable insulation and in the conditioned space. Remember, during the heating season, all of that energy goes to helping heat the house.
This means the standby loss is in the range of roughly 10% of the total hot water bill (without the affect of the heating season).
Now to finish the perspective, you need to divide the NET cost (new tankles minus tank style) of the new water heater by this savings to get a payback.
If you have a working water heater, it makes NO sense to switch for the purpose of savings. If you NEED to replace your old water heater, then you have your choices. The difference between the installed cost of the choices divided by the savings gives you an idea of how good of an idea it might be. If the tankless costs e.g. $500 more, and you have a savings of say $20/yr ... that is a 25 yr payback. Better than PV solar systems, but not as good as other energy saving options.
So, I stand corrected on previous statements of 'miniscule' savings. Pay your money take your choice. I don't advocate one or the other ... only informed decisions.
I stand behind my previous comments, however, with respect to the 'substantial' savings that is often the selling point of tankless. I don't consider 10% substantial, but that is just me.
People who claim their bill went down after replacing an old fashioned worn out water heater w/ a tankless ... are right ... substantial savings. However they aren't comparing apples to apples. A tank style efficient replacement would have achieved say 90% of their savings. Much of the savings is in the increased combustion efficiency of the newer appliance regardless of tank or tankless. So you really can't claim tankless savings on those examples.
"A 'typical' family of four
"A 'typical' family of four might use from 50-60+ gallons of hot water/day according to a couple of sources I googled."
That's one difference - I'm talking about a family of 2 that uses less than half that.
"of that, the standby loss for e.g. a 50 gal tank would be about $25 and $20 respectively for the standby loss assuming reasonable insulation and in the conditioned space. Remember, during the heating season, all of that energy goes to helping heat the house. "
I disagree there as well - hot water heater is in an unheated basement, so none of the lost heat goes to heat the house. I calculated and measured standby losses much higher than the 15% you assumed.
"Now to finish the perspective, you need to divide the NET cost (new tankles minus tank style) of the new water heater by this savings to get a payback. "
In my case, I used (tank style - tankless) since the net cost installed of the tank style would have been higher.
"If you have a working water heater, it makes NO sense to switch for the purpose of savings. "
Disagree there as well. If the tank style is beyond it's warranty, the risk of tank ruptures seems to increase, leading one to consider replacing. Replacement costs (at least in this area for my situation) were roughly comparable, with the tank style slightly higher in cost. HOWEVER, the federal tax credit made the tankless the clear winner - it was not possible to recover the increased cost of the tank style over it's expected life when the tax credit was considered.
YMMV, etc.
There is nothing to disagree about. I didn't make absolute statements ... only statements that IF the condition exists, then my calcs and statements are based on those. As I said ... all technologies have a place. The trick is to make a truly informed decision based on YOUR situation/conditions.
A family of two ... should maybe compare w/ a 40 gal tank max. I'd think, so the standby losses are commensurately smaller. If you are in an unheated basement, then I understand, but some of that heat loss does minimize your house heat loss (i.e. through the floor) by raising the basement temp (even if very little). The standby loss is relaitvely easy to calc and yes, it will be higher if the tank is in an unheated basement (I call it a tempered or buffer space as it isn't outside temps, either). Assume the basement is another 10 Fdeg colder.
Your new tank style installed cost would be higher? That would be a bit unusual, MAYBE (again, depending on the situation and what you compared it to). The only tank style that might compete cost wise would be a condensing tank style, I would think.
If you are worried about your existing water heater giving out soon, then you are theoretically ready to replace it and you don't really consider it a 'working unit' still within its useful life.
Just trying to keep a perspective here and you seem to want to pick apart everything I say as if I made absolute statements. I qualified my statements, so there is nothing to disagree about.
If there are tax credits or other rebates available, obviously it skews the economics. Bush gave tax credits for gas guzzling SUVs ... that don't mean it's a good thing to do.
The current add at the top of the page boasts energy savings from tankless ... I wonder how much they inflate the figures. Sure there are plenty of times that you can get 'big savings', but for the average household, I doubt it.
"You can actually and fairly easily calculate how much the standby losses are. I've done it and generally speaking, it ain't much"
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I guess it depends on what you see as "not much" - studies and experience suggest the standby loss is around 19% of total energy consumption. FWIW, my energy savings when I switched to the tankless was more like 30%.
If you draw water infrequently - for example, two adults, no kids, draw water mostly in the morning and evening, not during the day - you are likely to see significant savings with a tankless. If you draw water constantly, so you aren't really paying the standby losses, you likely won't see much energy savings. It's really just that simple.
My calcs on standby losses have routinely produced a standby loss of like 1%+/-. Drawing water infrequently to me means maybe every few days or once a week. A couple of times a day is as normal as anything ... and you will not see "significant savings" using a TWH over tank style in the use pattern you describe. If you saved 30% on the switch, the savings is likely due to the increased efficiency of heating the water (i.e. combustion efficiency).
If your old tank was uninsulated (I grew up w/ a bare steel tank) and sat in an unconditioned space, then your standby loss savings would be significant ... as it would be if you purchased a good insulated tank style.
Most often water heaters are w/in the heated space (or a tempered basement). Standby losses are generally small. It's really just that simple.
My calcs on standby losses have routinely produced a standby loss of like 1%+/-. ...and you will not see "significant savings" using a TWH over tank style in the use pattern you describe.
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You are certainly entitled to your opinions, but that information and conclusion conflict with independent studies, my personal experience, and my engineering calculations.
I'd be interested in reviewing your calculations - something is very different from my calculations and experience if you are only calculating a 1% loss.
FWIW, prior to switch to the tankless, I accurately calculated my standby losses. I happened to be travelling a lot, so in the summer when the only gas appliance active was the hot water heater, I measured gas consumption when I was gone for several days and compared consumption to when I was home and using hot water. With that information, when I switched to the tankless, I was able to repeat the process to document my energy savings.
In fairness, about 10% of the savings was simply due to efficiency - if I had replaced a high efficiency tank hwh, my energy savings would only be about 20%, not the 30.8% I actually measured.
see my reply above. guess I replied to the wrong poster.
I picked it off a rack during lunch at a design review with one of our government projects a couple years ago.
I need to go back in January so I'll try and track it down - they never throw anything away.
I put in a tankless about 5 years ago. The savings is about 10 dollars a month so not much. I have a rancher style home so it did free up a lot of room in the laundry room for us. But there are no downside to it so far.