Tankless info from consumer reports, Tankless...Bahhhhh

Discussion in 'Tankless Water Heater Forum' started by nhmaster, Dec 29, 2008.

  1. nhmaster

    nhmaster Master Plumber

    S. Maine
    This is out of Consumer Reports.

    Heating water accounts for up to 30 percent of the average home's energy budget. Some makers of gas-fired tankless water heaters claim their products can cut your energy costs up to half over regular storage heaters. So is it time to switch?

    Probably not. 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. But because they cost much more than storage water heaters, it can take up to 22 years to break even—longer than the 20-year life of many models. Moreover, our online poll of 1,200 readers revealed wide variations in installation costs, energy savings, and satisfaction.

    With the help of an outside lab, we pitted Takagi and Noritz gas-fired tankless water heaters against three storage water heaters. EvenWe didn't test electric tankless heaters because many can't deliver hot water fast enough to replace a conventional water heater if ground*water is cold. in areas with warm groundwater, most homeowners would need to upgrade their electrical service to power a whole-house tankless model.

    Our tests simulated daily use of 76 to 78 gallons of hot water. That's the equivalent of taking three showers, washing one laun*dry load, running the dishwasher once (six cycles), and turning on the faucet nine times, for a total of 19 draws. While that's considered heavy use compared with the standard Department of Energy test, we think it more accurately represents an average family's habits. We also ran more than 45,000 gallons of very hard water through a tanked model and a Rinnai tankless model to simulate about 11 years of regular use.

    Here's what else we found:

    Water runs hot and cold
    Manufacturers of tankless water heaters are fond of touting their products' ability to provide an endless amount of hot water. But inconsistent water temperatures were a common complaint among our poll respondents. When you turn on the faucet, tankless models feed in some cold water to gauge how big a temperature rise is needed. If there's cool water lingering in your pipes, you'll receive a momentary "cold-water sandwich" between the old and new hot water. And a tankless water heater's burner might not ignite when you try to get just a trickle of hot water for, say, shaving.

    Nor do tankless water heaters deliver hot water instantaneously. It takes time to heat the water to the target temperature, and just like storage water heaters, any cold water in the pipes needs to be pushed out. And tankless models' electric controls mean you'll also lose hot water during a power outage.

    Up-front costs are high
    The tankless water heaters we tested cost $800 to $1,150, compared with $300 to $480 for the regular storage-tank types. Tankless models need electrical outlets for their fan and electronics, upgraded gas pipes, and a new ventilation system. That can bring average installation costs to $1,200, compared with $300 for storage-tank models.

    Tankless units might need more care
    During our long-term testing, an indicator on the tankless model warned of scale buildup. We paid $334 for special valves and a plumber to flush out the water heater with vinegar. Many industry pros recommend that tankless models be serviced once a year by a qualified technician. Calcium buildup can decrease efficiency, restrict water flow, and damage tankless models. Experts suggest installing a water softener if your water hardness is above 11 grains per gallon. Ignoring this advice can shorten your warranty.

    Efficient storage models are pricey
    We also tested the $1,400 Vertex, a high-efficiency storage water heater by A.O. Smith. The manufacturer claims its installation costs are similar to a regular storage model. But its high cost offsets much of the roughly $70 per year the Vertex will save you. Instead, we recommend buying a conventional storage water heater with a 9- or 12-year warranty. In previous tests, we found that those models generally had thicker insulation, bigger burners or larger heating elements, and better corrosion-fighting metal rods called anodes.

    Posted: September 2008 — Consumer Reports Magazine issue: October 2008

    So basically Consumer Reports is verifying pretty much everything those of us that have been screwing around with these things have been saying. Believe me, we have seen these products 25 years ago and had allthe same issues with them. In fact, most of those have long since been scrapped for more conventional heaters.

    Indirect heaters use a boiler to heat a quantity of hot water. The storage tank is super insulated and has very very low standby loss. The recovery of these units if properly sized will allow you to virtually run hot water all day long.
  2. jimbo

    jimbo Plumber

    San Diego
    I am happy to see that article. There are people who love tankless, and more power to them. Sometimes, you are made to feel like a heretic or a luddite for opposing tankless.

    I have always maintained that the ONLY advantage possible with a tankless is that MULTIPLE folks can take sequential showers. Or you can fill a large tub. These applications are where the 70% rule on tank heaters catches up with you. But for most homes, forget it . The payback time is LONG.

    I can remember some places I stayed at in Hong Kong had tankless heaters...it was literally IN the shower....hanging right there on the wall. It put out HOT water, right away. I suspect it did not have a lot of the safeties that today's units do, so the water came on hot and stayed hot. It was great! I imagine that the space savings in small apartments, and saving on running all that hot water pipe everywhere....was the reason for using them. I don't remember, but I don't think there was anything but cold in the sinks.

    I agree with CU's usage numbers. I keep spreadsheets of water usage in my condo comlex ( we have usage issues!). Over a couple of years data, our usage runs about 165 gallons per day, per unit. Now the units are a mix of 1 and 2 BR, one to 4 persons per unit ( occasionally 7 illegal aliens in one unit!). 2BR units have 2 baths, all units have DW and WM. So the data is blended. This number does not include landscape, which is on a separate meter.
  3. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Chicago, IL
    I recall when tankless first came out. Their huge claim to fame was that they been in use overseas for over 50 years. They fail to say the reason they been in use for that long over there is most places do not have room for a storage tank. Now Bradford White came out with a water heater that can deal with the high demand like filling a hot tub. A 25 gallon water heater puts out more hot water in the first hour than a standard 50 gallon. Here is the spec sheet. http://www.bradfordwhite.com/images/shared/pdfs/specsheets/115-B.pdf
  4. Ian Gills

    Ian Gills Senior Robin Hood Guy

    You are missing an important part of the space advantage in their use overseas.

    Most countries use a tankless combination boiler that provides hot water for the faucets and hot water for the heating via radiators.

    So they really are much better than the seperate water heater and furnace that you use here in the colonies and that I have, too, in my colonial home. In Great Britain, the combination tankless boilers are far smaller and they last just as long too.

    The only drawback is that without forced air, most of these homes do not have AC but it is a colder climate anyway.

    Worcester Bosch make the best tankless combination boilers in Europe.

    Forced air heating solutions in Europe date back to the 1970s. They are considered extremely dated and (most of all) expensive to run.
    Last edited: Dec 29, 2008
  5. Ladiesman271

    Ladiesman271 Homeowner


    Glad that I have a pilot type tankless gas water heater. Instant ignition of gas burner to full on, no cold water sandwich, no electicity needed, and can be used when there is no power.

    As far as that "trickle" test is concerned, I have never had that problem either. With 70 feet of insulated 1/2" pipe, it does take about 1 minute to get full temperature at the furthest outlet. About 30 seconds for warm water to get there.

    I also needed the floor space that the old tank took up!

    Tutorial on tankless water heaters - click here!

    Last edited: Feb 23, 2009
  6. Cass

    Cass Plumber

    Yup...this echos everything that has been mentioned here since they first started becoming popular...
  7. Smith333

    Smith333 Member

    They just had an episode of Ask This Old House on where the resident plumber replaced a tank heater with a tankless, showing the step by step process as if an experienced homeowner could tackle the project. They never explicitly said it was a DIY project, but they didn't explicitly advise against it either. And while they didn't verbally name the heater, the "Rennai" label was shown prominently during the install.

    Of course, they also conveniently side stepped all of the issues discussed by the CR article and the plumber went so far as to suggest blanketly that anyone with a tank heater over 7 years old should replace it with a tankless, and implied that the savings in gas would definitley payback the increased upfront costs.

    Way to go PBS with your unbaised, objective, sound advice.
  8. ArtM

    ArtM Junior Member

    East Slope of the Rockies
    Well, I won't pay retail for a tankless ;) ... But, it may make sense for one of my layouts.

    We have a family country place that is in need of a complete plumbing overhaul. We leave the heat on (moderately) all the time (winter) as we never know when someone may be dropping in to use the place for a day or week. Sometimes the place won't have visitors for a week or two - maybe even three. Then we may have a family get together with a houseful of people.

    I dislike seeing the tank water heater going all the time the place sits empty. But, I really dislike taking cold showers - which is usually what happens when the tank heater can't handle so many people in a row.

    Think the upfront expense might be worth it - for the hot shower if nothing else (yes, I'm usually the last guy in line).
  9. Fubar411

    Fubar411 New Member

    St Louis, MO
    Helped a buddy with his country place. We just put in a smaller electric water heater. Part of the instructions for starting the place up include flipping the breakers for the well and the WH. It is amazing how quickly a 40gal wh gets hot, even with just electricity.
  10. gregsauls

    gregsauls Homeowner

    Getting my Rinnia at cost plus was a benni.... add the US tax credit for 2009 as another benni. It all adds up to a good investment for me. YMMV.
  11. ArtM

    ArtM Junior Member

    East Slope of the Rockies
    Makes sense, but one can't get very many back to back showers out of a 40 gal electric tank. At our place, after six or eight of us have been running through the mountains all day, we all would like to shower before evening cards and games. So I'm thinking tankless may have its place - even though it certainly isn't the answer for all hot water applications.
  12. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    South of Boston, MA
    I don't have gas to the house, so tankless wasn't an option
    I need my 200a service for my Christmas display :eek:
    We had a 30g oil fired that let loose
    Oilman said to replace it would be $1900 - but it would be the last one I bought. Instead we went with a 95% efficient 50g electric model. I don't have a clamp meter, not sure how much it uses a month
    With the cost of Oil (we have oil heat) it made sense

    I'm going to add a solar hot water heater for summer use
    I also want to add another tank to allow ground water to warm up before it enters the WH

    I like the idea of tankless, but have just heard too many opposite opinions of how well (or not) that it works
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    If you mountain water is ice cold coming in the house in the winter, you will probably not be very happy with the tankless. Like a hand through a flame, a tankless can only heat so much (raise the temp), and the colder the source water, the colder the outlet.
  14. ArtM

    ArtM Junior Member

    East Slope of the Rockies
    Good thought. Thanks for mentioning it. We've a well that has a pretty consistent temp summer or winter. Unsure what the temp of it is - but it isn't ice cold. We'll be out there next weekend. Think I'll measure the temp and find out what we're dealing with.
  15. Ladiesman271

    Ladiesman271 Homeowner


    I disagree. Most tankless heaters do have a thermostat. My water temperature coming in is now 40 degrees, and my older 125,000 BTU tankless has no problem at all delivering 125 degree hot water to the last fixture.

    I admit that I can not take three showers, do laundry, and use the dishwasher all at the same time. Then again, I have never needed to do that either. I don't think that the cold water can maintain pressure if I have all those units on at the same time either!
  16. chris8796

    chris8796 New Member

    Crunching the numbers, it looks like you can heat ~2.2 gal/min with a 85 F temperature rise. So your right at the edge of your capacity. But, overall I think this would be a good application for tankless WH.
  17. rwcarpenter

    rwcarpenter New Member

    I noticed some whole house 4 bath electric tankless require 300A service...so your 200A would not be enough for those (3x60A). I have decided that the ones that work on 2x50 and 2x60 circuits would not be all that great due to my cold ground water (very cold deep well water).

    I am however considering a couple of 30A tankless as boosters for a couple of my showers (or one 40 or 50 amp one since they are close and on same line). Its a long run and takes longer to get really hot water from other end of house than to take a shower, so its either take a lukewarm or cool bath or wait. What do you guys think of them for that application (that is localized boost heating)?
  18. Ladiesman271

    Ladiesman271 Homeowner


    In reality I am not at the edge of my hot water capacity. You are accurate in that my gas water heater is rated at 2.09 gallons per minute @ a 90 degree temperature rise. That is pretty much identical to your calculation.

    This morning I measured the water consumption while I was taking a shower. With everything set for a normal shower, I used about 1 gallon per minute of water during the shower. About 1/3 of that water was cold water (40 degree temperature).

    So, the way that I see it I have plenty of water heating capacity to spare. The use of about 2/3 of a gallon per minute of hot water during a typical shower does not strain the heater at all.
  19. Ladiesman271

    Ladiesman271 Homeowner


    I have my doubts about the use of a central tankless powered by electricity. Some utilities do not permit them to be used due to the heavy peak power demands they require when they are in use.

    For central electric, I would go with a tank type water heater.
  20. Dana

    Dana In the trades

    That CU article was more than just annoyingly bad- it's downright disinformational!

    In reality, if you use less than 60 gallons of water/day, your tank HW heater will perform LOWER than it did in an EF test (and far lower than the high-volume test the CU folks performed.)

    Similarly, if the bulk of your water is a gallon or less at a time (say, primarily for hand-washing, and you only wash clothes or take baths once/week), your on-demand won't meet it's EF numbers, may even perform lower than a decent tank (but not likely.)

    There's a ton of information (prolly more than you ever wanted to know :) ) on the subject here:


    For the true tankless performance, take a look at Fig 5.1 (p. 48 of the .pdf, or 42 of the printed document). At 2 gallons/draw it's no better than a tank's EF performance, but it'll clean the tank's clock at anything over 5 gallons/draw.

    Here is more succinct & graphical comparative test summary from PG & E than the WHPAGette_Final.pdf document that demonstrates just how much of a difference actual use patterns effect operating efficiency (and how truly sucky standard-efficiency tanks perform relative to their EF numbers at low & moderate levels of more realistic use than an EF test):


    Even one of the CONDENSING tank systems (heater #4) couldn't muster 70% under moderate use(!), and in the mid 60s under low use. The only tankless that was tested was a condensing version (heater #6- they didn't specify whose that was), and it too suffered slightly under low use, but not nearly as severely as standard efficiency tanks or even the crummier condensing tank. The only one that beat all of it's standardized tests under all conditions was a (definitely not cheap!) stratified condensing tank (heater #5).

    I kinda wish they'd tested at least on of the standard-efficiency tankless units in this comparison, but it is what it is. The low mass of a tankless keeps it from falling off a cliff the way tanks do under low use conditions, but the low-use profile they used has a larger fraction of the total test volume in draws under 2 gallons (where tankless performance gets killed)- I suspect a standard efficiency tankless would have a similar degradation to the condensing tankless- subtracting 5-8% from the condensing version's performance is probably reasonable, meaning that in heavy use it'll be in the low 80s, moderate use around 75-78%, and low use around 70%- still better than the low-tech tanks under their best-case heaviest use.

    The tank heaters DO fall off an efficiency cliff! None of the non-condensing standard-efficiency tanks (heaters 1-3) tested actually met their EF numbers in moderate-use profile, although they beat their numbers in heavy use profiles. If you're an on-the-go 1-2 person family that often takes weekends away (or only bathes once/week) the tankless is a far superior option. But the stay at home family doing 2 loads of laundry every night after the kids go to bed will still see an efficiency gain with a tankless, just nothing like multiplier the on-the-go single/couple experiences.

    So, it kinda depends- if you're on the go, living alone (or a water-sparing couple), often take weekends away etc, you'll likely meet or beat your tankless EF numbers by a few percent, but won't even come CLOSE to your tank's (lower) EF numbers. If you're a mostly stay at home family of 5 you'll likely meet or exceed the EF numbers for either, and the Consumer Reports analysis could be correct, but is it? No way to tell- the don't specify price & inflation assumptions. But check your actual fuel costs- they vary considerably with location. Here in MA we pay 2.5-3x the rate for natural gas as they do in UT.

    For as-used efficiency comparisons, gas-fired tanks are all about maximizing the total consumed volume. If that's you/yours, great. But if its not, your actual efficiency isn't anywhere NEAR what the nameplate or EF number say. Getting efficiency out of a tankless is only about minimizing the number of very-low volume draws.

    But the real reason to go tankless is to save your marriage- you never hear the screech from your spouse about the cold shower (did they factor in the cost of a divorce in the financial model for the tank? :) )

    In the Consumer Reports article they deftly dances around the longevity & service issues too- they didn't add in a full -replacement of the tank heater, simulate only an 11 year use (by excessively hardening the water- which is also a dubious method) yet say it "can take up to 22 years to break even—longer than the 20-year life of some model". In my accounting book I'd have to double the purchase & installation costs of the tank, yet apply only a 1.25 multiplier to the tankless. Tanks RARELY give 20+ years of best-efficiency service before out & out replacement replacement is required whereas tankless burners are easily serviceable (even heat-exchanger replacements), and the bulk of the "extra" installation costs are presumed electrictal outlets for the powered venting & controls and presumed gas line capacity upgrade. A full replacement of the tankless after 20-25 years of service won't be NEARLY the numbers quoted, since electrical power, gas lines & stainless flues etc. would already be in place- it'll be about the same as the tank. In many instances the gas lines might already be big enough to deliver, needing no upgrade.

    It's true that while it's easier to service, the tankless will likely NEED to be serviced at least a couple of times in 20 years (I've got one that's 15 years old and going strong without any service beyond brushing out the heat exchanger once, but it's less complex than the Noritz & Takagis they tested). But then again, is swapping anodes every years and annually draining sludge from your tank really less work than swapping filters & occaisionally checking for lime scale on the tankless, cleaning as-necessary? It's a crap shoot, sez me, but in most situations the efficiency of the tankless will be better. Whether it ends up being totally dollars & cents cost effective is something you'd need to analyze, but I've yet to hear from anybody who went back to a tank after living with a tankless.

    If you're considering it ever, PLEASE do a better job of the analysis than the Consumer Reports folks, eh? They adequately explain neither their test procedures nor their financial analysis, projected fuel prices, etc.. I found the article pathetically devoid of essential detail, and high on "we know better, and thus recommend..." attitude. (Can't say I'd recommend buying their mag, eh? But I s'pose I'm just coppin' an attitude myself. ;-) )


    ...there's another FAR better option for many:

    If your space heating system is done with a mid-efficiency (83%+) or higher hydronic (pumped hot-water) boiler, an indirect-fired HW heater running off the boiler will give you similar performance for less money, without the cold water sandwich. Done right, it should be capable of keeping up with continuous-demand of back-to-back showers (even with guests), just as a tankless would. And by increasing the duty-cycle of the boiler, it would improve the overall heating-system efficiency.

    Standby losses of an indirect are far lower than that of a selfstanding gas fired tank, since the plumbing penetrations are small so it can be fully & insulated (the selfstanding has flue & burner penetrations & clearances to contend with) it doesn't have a flue to convect heat out of the tank 24/7, or a pilot light burning 24/7 (literally half the gas consumption of the heater for many 1-2 person families.)

    Indirect fired tanks off the hydronic boiler is THE way to go whenever it's an option. Beyond that, you'll get better performance out of an on-demand. If the cold-water sandwich is too much of an annoyance, there are moderate-cost adder ways around that too:

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