Wednesday, July 27, 2011

Tankless vs. Tank: the water heater debate







VS.








Early on we realized that our home renovation would mean replacing our hot water heater.  Not only was it older and less efficient but it is a natural gas heater without closed combustion.  LEED requires that all combustion heaters have a sealed air supply and exhaust duct.  This is a safety / indoor air quality issue as open combustion appliances may result in combustion gases or exhaust entering our living space.

Knowing we had to replace it left us with the decision between a traditional water tank or a tankless water heater.  The difference?  A traditional water tank heats up water and stores it until you need it.  A tankless heats water as it passes through the heater.

There is a lot of debate about which is better and a lot of mixed reviews from tankless users. Looking through the complaints though I think a lot of the problems were false expectations about what a tankless can provide.

Tankless Advantages

Energy Savings
Realistically we probably only use hot water in the home a couple hours of the day for washing and showering. The rest of the time the tank is still expending energy to keep it hot for us.  Since tankless units aren't storing any hot water they have no standby losses which can typically account for a third of all energy loss.  Some studies have even shown over 50% energy savings by switching to a tankless unit from an older tank.

Space
Again since you are not storing any hot water you don't need something that is 50 gallons in size. Tankless units mount on the wall and are only a couple feet square thereby freeing up potentially valuable floor space.

Endless Hot Water
No more running our of hot water in the shower. Since the tankless provides the hot water on demand it will never run out.  The tankless will however have a maximum capacity so make sure it is sized correctly.  If you get one designed to provide water to two showers don't be surprised when the water runs cooler when you have two showers and a washing macine and a dishwasher all going at the same time.

Cleaner Water
Anyone who has every drained an old hot water tank will tell you that the water in there is not pristine.  Over years there is a lot of rust and build-up down there. Not an issue with the tankless.

Longer Life
Most manufacturers list this as a benefit.  I am not sold on it but I suppose it could be true if you followed the US Department of Energy recommendation of replacing your water tank every 7-10 years.

Tankless Issues

Cost
Tankless units cost more because they are more complex requiring electronics not found in standard tanks. Some of these costs can be offset by government subsidies available most places.  In Quebec for example, there is a $450 rebate from Gaz Metro for switching to a tankless unit and the federal government's relaunched EcoEnergy program will kick in another $375.  This definitely brings the costs in line with traditional tanks.

In colder climates (like Canada) the incoming water temperature is low.  This means a higher temperature jump to heat the water up and virtually eliminates electric tankless units for whole home systems.  Natural gas units can provide much higher BTUs but will cost more to have installed.

It should be noted that the higher cost will be offset by the efficiency gains. Pay more up front but save on the gas bill.  There are endless discussion room threads however about whether you will ever make back your investment and a 2008 Consumer Reports article suggests you probably won't.

I suggest you take a look at the math for you and your situation taking into consideration any and all subsidies that may apply.

Time Delay
One of the biggest complaints about tankless units and what most sales people never prepare consumers for is the speed of delivery of hot water.  (it doesn't help either that tankless systems are often referred to as "instantaneous water heaters")

When you turn on your hot water tap, the water startes to move down the pipe and the tankless system detects the flow rate.  It then fires up the burners, heats up the heat exchangers and starts heating the water which still needs to flow through the pipe to your faucet.

That all takes time so it will take longer to get hot water to your faucet than with a tank.  Some people find this wait unacceptable.

To combat this some models have a small buffer tank built in, this allows for hot water to start flowing right away at minimal flow rates. So if wait time is important to you search out that option.

Water Sandwich
The buffer tank also resolves the other big issue with tankless heaters:  the Hot/Cold water sandwich.

Here is the scenario: get up in the morning and run some hot water in the sink.  Heater fires up. Water heats up. All is good.  Heater turns off.   You hop in the shower and there is still hot water in the pipes.  Meanwhile cold water flows through the tankless sytem while the minimum flow rate is detected and the system turns back on.  You end up with a short blast of cold water mid-shower.

Obviously, people whose system and habits makes this happen are not happy with their tankless systems.

Maintenance
As there is more complexity to the system there is more that can go wrong: circuit boards, flow detectors, control valves.

While you no longer need to drain and clean the tank you do need to clean the filters and possibly de-scale our unit every couples years

Our Decision
For a long time we were firmly on the fence about which way to go but it ended up being a relatively straight forward decision.  We have one luxury that we enjoy that doesn't quite mesh with a fully "green" lifestyle: a nice hot bath.  In remodeling our bathroom, we added a nice deep tub to soak in... an 80 gallon tub.  Running the first bath, the water went cold half way through.  We aren't about to install a giant water heater for a once a month luxury bath so we will be going tankless (and yes ours will have a mini-buffer tank).

66 comments:

  1. The only issue we have had with our tankless heater is the hot water delay. You get used to it. A couple of times there was the "hot/cold sandwich" but I mean once or twice in several years. I'm glad we are not paying to have a water tank bubbling all day. The tankless is really great when we have guests over, especially after skiing or hiking. You can have five people shower in a row and none of them have to go without hot water.

    ReplyDelete
    Replies
    1. When shopping for a water heater, there are many things to consider, including efficiency, convenience and cost.

      Efficiency - Traditional water heaters devour a lot of energy because a constant supply of heat is needed to keep the stored water hot, even when you are not using any hot water. Tankless water heaters only use energy as you use hot water, making them the more energy-efficient option by a landslide.

      Convenience - Generally speaking, a tankless water heater is more convenient because it eliminates the dreaded last-one-up-gets-a-cold-shower dilemma. Tankless water heaters can also save you space, where traditional water heaters typically require a larger amount of space. These compact units can be mounted on a wall, inside or outside your home and supply hot water on demand.

      However, some tankless water heaters are too small to supply enough hot water for simultaneous use. For example, if you were showering, running a load of laundry in hot water and washing dishes in the dishwasher, you could be demanding more hot water than the tankless water heater can supply. (Traditional water heaters would also have a difficult time keeping up with such strenuous demands.) You can avoid this by installing a higher-rated tankless water heater or choosing to install multiple units.

      Cost – While tankless water heaters are slightly more expensive, they recoup the cost of their initial installation over the course of their lifetime from decreased energy bills and a longer lifespan. Traditional water heaters are still common because they can be significantly less expensive. But they are also more expensive to operate.

      Delete
  2. This one is extremely looking one of the fabulous information post about Tankless Vs. Tank. And according to me, Tankless water heater is really the great option than this one. Because of, this one really creates the option for endless water. The regarding information of this post is really looking incredible. Thanks for sharing.

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  3. Most households use tank water heaters mainly because they're more affordable than the tankless ones. We have been using one for our home ever since. But I'm open to the possibility of using a tankless water tank if I get rich! =D

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  4. This comment has been removed by a blog administrator.

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  5. We still use our water tank heater. It's still working properly, and that's why we haven't considered buying a new one. Our traditional tank has never failed us since we bought it when we moved in. We never had a problem with water leaks and malfunctions.

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  6. My previous house was a new build and I went for the tankless. The features I liked were that it was totally silent, unlike a hot water tank with a blower that cycles on and off all the time. I'm in a northern climate so had I stayed in the house, I was going to add a small electric buffer tank that is at room temperature. However, if you run a long loop of pvc tubing between the tankless and the entry point of the house, that would probably be more than sufficient. Ambient air will pre-heat the loop and by the time the really cold water reaches the tankless ( say 30 seconds ) it'll be at maximum heat and ready for it.

    Another trick was that you would can often remotely adjust the temperature output at the bathroom. You would then only use hot water ( no mixing ), so if someone flushes elsewhere in the house, you might get a slowdown, but not a change in temperature.

    Similarly, the output can be made hotter when doing dishes.

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  7. This comment has been removed by a blog administrator.

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  8. A
    tankless water heaters
    is not instantaneous. It does take them about 2 seconds to go from their at rest "off" mode to producing hot water at the set point temperature. Tankless water heater may be mounted on walls, and are ideal in manufactured homes where space may be limited.

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  9. It's a good thing that you have decided to buy a tankless water heater for your home. This can provide you more hot water, and it is energy-efficient at the same time. However, you need to have a yearly maintenance to prevent water flow restrictions due to calcium build up. You may also consider installing water softeners to reduce the concentration of calcium in your heater.

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  10. This comment has been removed by the author.

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  11. Indeed a healthy debate on water heaters. I am with tankless. It is very efficient and energy saver as well. I am looking for best repair services for tankless water heater in Canada.

    ReplyDelete
  12. Tankless water heaters are more and more in demand in today’s life and requirements, because of their affordability, effortless application,
    consistency and the majority of all the functionality to provide a never-ending stream of scorching water. Thank you for posting this...

    ReplyDelete
  13. We have a hot-water-on-demand propane water heater. We can’t take any credit for this since it was in the house when we bought it, but oh my goodness we love it. chino hills plumbing

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  14. This comment has been removed by a blog administrator.

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  15. I'd much rather wait a few minutes for the hot water to come out rather than make a fiasco on where to place the tank. I usually turn on the shower then go and brush my teeth while waiting; you get to do two things at the same time. Of course, I choose the tankless water heater. No more running out of hot water and I have a cheaper electric bill.

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  16. Thanks for telling us difference between heater with tank and without tank. Your information provided is good and it will help persons who have no knowledge about this.

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  17. Comparing those two will be an absolute issue but for me based on my experience a tankless water heater has a much higher electric consumption than a heater with tank. Having a water tank will save you a lot in your electric bills.

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  21. A tankless heater uses energy to heat water only as it is needed, so energy is used efficiently and utility costs may decrease. Plus, tankless water heaters can provide a steady stream of hot water that doesn’t run out.

    ReplyDelete
  22. Electric tankless heaters require a relatively high electric power draw to heat colder water quickly and for that reason they provide a lower flow of hot water and may require installation of additional electric power to the location of the heater and perhaps more service to the house itself.

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    ReplyDelete
    Replies
    1. You are right, and in a lot of colder climates it is not even feasible with a pure electric heater. Ours in natural gas and has Ben working well.

      Delete
  23. I also decided to have a tankless water heater because I have a big household. All of us can take bath using hot water without it running out. I agree there is a short delay from cold-hot water, but it is okay to with me to wait for just a couple of seconds. You’ll get used to it.

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  24. A very descriptive debate, I think Rinnai tankless water heaters are good, or may be with tank water heaters by Rinnai could also be good, but I'm using the tankless one that's why I'm with it.

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  27. On demand Solar water heater are amazing. I've experienced them a couple of times and the benefits are huge. It is a small unit, the water is as hot as you want and you save massive amounts of energy keeping all that water hot in your tank.
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