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Tankless water heaters: pros and cons

DoeringtanklessI’ve interviewed a dozen or so people who have installed tankless water heaters (which heat your water on demand rather than storing hot water in a tank) — and several contractors who have installed dozens more tankless water heaters — and the comments I’ve heard about the devices have been overwhelmingly positive.

And yet . . . as I peruse homeowner reviews of tankless water heater on the Internet (here and here), I see a different story. I see lots of pros, but also lots of cons.

Here are some positive comments:

Never run out of hot water, good for the environment, saves energy, takes up next to no space, earthquake safe, good for cottages, good for one-person households, good for spatially challenged areas.

And here are some negative comments:

Don’t meet high water demands of North Americans, needs maintenance plan factored in, installation difficult, you won’t notice any savings right away, plumbers are unfamiliar with them, sensitive to water pressure, turn on too much cold water (like flushing toilet or using clothes washer) and the heater shuts off.

What do you think? Do you have a tankless water heater? Any suggestions for those of us considering one?

Related posts:

Ask a Green Builder: Why is tankless water heater so noisy?
On-demand water heaters: A homeowner’s experience
New on the market: Mini on-demand water heater


15 Comments on Tankless water heaters: pros and cons

  1. We almost got one this year to replace our rusting out tank. The reason we didn’t was the cost, not just of the water heater itself, but the install costs would have been more than the price of the heater!
    I think if you are building new they are a great option. You can always get more than one, like for under sinks and such, which would help with the water usage problems.
    We ended up getting an energy saver tank water heater. It’s been great so far, and has cut our energy bill. I think it’s a great option for already built homes.

  2. I installed one myself and the only complaint is that you run through about a gallon or more cold water before the hot water gets to the faucet. In the summer the extra water can be used to water the plants I suppose!

  3. It’s definitely true that tankless water heaters aren’t for everyone. They save energy, can save water, save space and provide endless hot water. I would say if you’re thinking about getting a tankless water heater do your research first to make sure that it’s really going to fit your application. A good place to start your research is tanklesswaterheaters.com, these guys really know their stuff and they won’t sell you something you can’t use.

  4. I’ve installed one tankless water heater, and it was no big deal. That one, and the one that I’ll install in my own house, are both small units capable of being served by the existing gas line and with convenient (and short) exhaust lines.
    Exhaust lines for tankless water heaters can be expensive, so be sure to include them in your cost estimates.
    At my parents’ house they opted for a tank water heater when it came time to replace, since the necessary exhaust for the tankless would have had to go up 20′ or more. It might have had to be actively vented as well. There is no more convenient place to put the water heater in their house, so they happily settled for the tank.

  5. Takai, a very good model (I’ve had 2) sells reconditioned models in their Irvine Office at about half the price. We had two in 20 years. Some hints: you need to find a plumber who works with these on a regular basis, and make sure they are properly vented.

  6. We plan to install 2 units in our upcoming full home remodel. Originally decided with a Rinnai system, but now we may swing towards Noritz with our contractors recommendation. Both models are electronic gas ignition with interior thermostat remote controls.
    My research revealed similar pros and cons. Venting, distance, and appropriate system sizing, are keys to cost and true efficiency. Starting from scratch with all new plumbing, I feel it’ll be worth the long term investment. One system outside the Master Bath with less than a 12′ run to all fixtures, and the other outside the Kitchen with less than a 10′ run to the sink. Longest stretch for both, serving a half-bath next to the kitchen – a 20′ run; and serving the guest bath near the Master – a 30′ run.
    Highest demand – shortest run. Exterior mounted units – easy direct venting. Esthetically, and fortunately, both units have somewhat inconspicuous locations.
    Would be interested to hear if there are experiences with these direct vent units.

  7. i haven’t done it yet, but my plan is to install a SOLAR water heater which feeds into a tankless as a “backup.” much of the time, the tankless will not even need to activate, and when it does, the “jump” in temperature will be much, much, lower, so it will hardly use any power, and i can get a smaller, cheaper tankless because of that.
    the secret is to get a tankless that can accept hot water coming into it, many can’t. i know the Takagi can.
    the state of CA is offering great rebates for the solar heaters now, if you are a “gas” customer (i’m not), so even though the Energy Star rebates expired (call your congressperson and demand they reactivate!!!), you can at least get the solar part in now for a good price. they are much, much cheaper than PV.
    NB – it does NOT need to be hot for the solar water heaters to work, so they work even in winter. We all need to participate in this new energy paradigm, so please consider solar at least for water heating…

  8. Kathy Price-Robinson // February 21, 2008 at 11:58 am // Reply

    Sheila, can you share the brand or type of solar water heater you will be installing and direct me toward a website where I can get info on costs and installation requirements. Then, I’ll make a posting out of it. Thanks!

  9. We put a Takagi TS1S in our house when we remodeled it. Prior to heating season, we ran the same or a dollar or two lower gas bill on our two person occupied house than the bill on my unoccupied condo. The condo has a tanked heater water heater which was on but was not being used.
    It was much easier putting the heater in when remodeling rather than adding it in later.
    We got around the slow delivery of water issue by putting in an on demand recirculating pump to get hot water at the tap without having any water go down the drain. it is only necessary at the far end of the house (kitchen and laundry room), and not in the bathrooms.
    I did look at putting a tankless in the condo when I replaced the water heater a few years ago, but the venting problems associated with the existing vent (from the garage out to a second story roof) ruled it out.
    I recommend them. You just need to know the differences between them and a tank. most of the criticism i have seen are related to those differences.
    There was an excellent article in Fine Homebuilding in the past few months on a recommended installation process and setup for tankless systems.

  10. I have five Takagi tankless units installed at my home, office, and rentals. All are now working well, by we encountered a number of issues when installing them. I’ve put together a web page about the problems we encountered and how to avoid them at:
    http://www.paragoninspects.com/tankless-heater-home-inspection-evanston-chicago-il-faq.html

  11. We installed a Noritz tankless unit when our old tank system failed. There are definite pros & cons. We found wildly different estimates from installers. So get a few bids if you are interested. The main installation issue is replacing the standard gas line with a larger one.
    Pros are that, once the hot water is running, you never run out. Great if you have a big family, have to do lots of laundry, dishes, etc. You get the environmental and cost savings when the unit is not running, because the system is truly off then and not burning gas to keep a tank hot. And the unit is smaller.
    Cons are that it does take longer for hot water to come out of the faucet, especially if its the first shower of the morning. You may also experience less water pressure and a lower temperature than you are used to with a tank system set at a high temperature. This issue can be solved by purchasing a larger capacity tankless unit. Certainly, cost is an issue. The savings accrues over time due to lower gas usage. However, because the unit has an electronic ignition, during a power outage the system will not work. be sure your installer knows all the permitting issues and includes the permit and meeting all permit issues as part of the bid. We ultimately had to hire an outside electrician to complete the work to code.
    An architect friend of mine is recommending using a small tank system, solar-based if possible, in conjunction with the tankless system. That way you have a reserve for quicker hot water.

  12. thanks for your interest, KPR, i will keep you informed, but it will be a minute before i can get the whole system in place. since i will not get any CA state rebates since i’d be offsetting electricity use or propane use instead of natural gas use (since the Gas Co has not made gas available to my area), I and many others are ineligible.
    I am spending much of my time working towards sensible energy policies in this state, and this is just one of hundreds of stupid, corrupt or lazy policies I am seeing. To make matters worse, I have to fight the “good guys” like NRDC and Sierra Club who have gotten into bed with the utilities and who are really preventing all of us homeowners from getting a piece of the Renewable Energy pie. it is horrifying…
    All that to say, i will definitely keep in touch about my system, and Craig mentioned the same type of thing at the end of his post…
    Thanks, Sheila

  13. We installed a Rinnai about 6 months ago and so far, have found no problems with it. It was an easy decision for us, given we had a home warranty and we chose the option of receiving a payment towards the purchase & install of a tankless instead of the tank replacement. Combined with the Federal tax rebates it was a no-brainer for us. We weren’t familiar with Rinnai before but through research found that they are one of the more experienced tankless manufacturers. Also, our plumber said that Rinnai insists upon company sponsored training for installation and service, which he had completed.
    We have yet to run out of hot water although I must also echo others that running the water until it reaches the desired temperature mitigates your “good” feelings about not wasting energy just to keep the tank supply warm. Given ours was a replacement it was easiest to install in the garage where the old one was. But, a friend who is a homebuilder typically installs 2 smaller models, usually one closest to the kitchen and laundry and another nearer the bathrooms.
    A possible solution, as someone above mentioned, is a recirculating pump. Additionally, the PBS program This Old House recently was in Austin, TX for their first green building project. In it, they installed a Rinnai tankless, a recirculating pump and a motion detector so that whenever someone walked into the bathroom the pump would start up, saving the electricity of having it running all the time.
    Oh, BTW, ours is a propane model, 8.5 GPM, electric ignition, installed outside, as we can choose given we live in a temperate climate. This alone saves hundreds of dollars as the venting is stainless steel and quite pricey. While it does blow off some hot air, no one will ever be in danger of burns if they were walking by. Also, must be mounted a minimum distance under the roof overhang, I think it”s 2 feet. We paid about $950, install kit (which you must purchase) was another $75 but includes service valves, which many other manufacturers won’t include and install ran about $450.
    Haven’t yet tabbed up the propane bills to compare to last year but they have arrived for deliveries twice and told us that we didn’t need any which resulted in a non-intentional smirk on my part I must confess.

  14. Anita Weaver // February 25, 2008 at 8:35 pm // Reply

    We have a Rinnai system and love it. It’s pretty much maintenance free (knock on wood!). It provides water to our guest and master bathrooms. It’s quiet and extremely efficient. We like it so much we’re considering replacing our remaining tank heater with another Rinnai.

  15. Since it takes longer to get hot water from a tankless water heater, you end up wasting more water while running it down the drain wating for the hot water. There are several add-on type hot water pumps that pump the water quickly to your sink or shower without running any water down the drain. The Chilipepper pump pumps 2 gallons a minute, more than enough to activate the tankless water heater, and then shuts off when hot water reaches the fixture.

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