I've just recently been seeing these advertised.  We currently have a gas water heater.  Are there any benefits of tankless over traditional other than space?  Any other insight on these units will be appreciated.

Blake

Pros:
-Constant hot water
-Gets rid of the large tank
-Energy efficient

Cons:
-Does not mix well with hard water. Meaning, if you have hard water then every six months you'll get so much mineral buildup the pipes will have to be removed and cleared. Soft water is fine though.

I have not heard anything good with electric types but all good stuff from gas water heaters of the tankless kind

Well, you would only heat the water when you need it, so you should save on gas.  You could also take looooong showers without having the hot water run out.


Vulcan94

How do they work?

When I lived in Germany, my house there had one.  I liked it for the reason that I had as much hot water as I needed.  The energy efficiency is what makes them popular there.  I was nearly twice what my parents here in the US were for electricity per kWh.  

I work at Lowes and there pretty popular there. seems like they run about 500 something. I wouldn't mind having one.

Quoted: Pros: -Constant hot water -Gets rid of the large tank -Energy efficient Cons: -Does not mix well with hard water. Meaning, if you have hard water then every six months you'll get so much mineral buildup the pipes will have to be removed and cleared. Soft water is fine though.

dont forget 3x the cost of a standered water tank,.... kinda nagates the "saveings"

Quoted: Quoted: Pros: -Constant hot water -Gets rid of the large tank -Energy efficient Cons: -Does not mix well with hard water. Meaning, if you have hard water then every six months you'll get so much mineral buildup the pipes will have to be removed and cleared. Soft water is fine though. dont forget 3x the cost of a standered water tank,.... kinda nagates the "saveings"

You're thinking short-term.  The savings over a standard water heater are long-term.


Vulcan94

Quoted: How do they work?

imagine a flame under your cars radiator.

theres a shit ton of fins that collect the heat, transfer it to the water, when its in use.

works great :)

you can take 2 hour long showers all the time :)

My apartment in Italy had one.  I liked it.  Hot water whenever, and for however long I wanted.

I have one that runs on kerosene. I also heat the house with a kerosene "Monitor" heater (and a woodstove). My total kerosene bill for my 2,300 square foot house in New Hampshire is about $600 per year. I wouldn't go back to the old type.

Cost and installation will run 2K, you'll need to make sure the [gas] lines are large enough to make sure there is no pressure drop, many places will NOT work on them. Parts are pricy, some will only deliver enought hot water to one faucet, not good in places where there is hard water unless softened. {CLR]

New traditional tank water heaters are pretty damn efficient and insulated very well. Heat loss is pretty slow and when you figure out the lifetime of each unit plus the pricepoint of each, you don't save a dime going to a tankless design. They are good if you have very little room or live in a warn climate where you tend to use cooler water. Heat up 40F well water and you'll find they are not all they are bragged up to be especially if more then one faucet is used unless you go top of the line which will cost you more $$$.

Until prices come down I won't even consider one, especially since a traditional water is usually cheap to repair UNLESS the control valve/thermostat breaks, at which time it's time for a new water heater. Bout 11-12 years is the average lifetime of a traditional water heater. [industry average taking into account different water types and usage.]

The simple facts about Tankless Water Heaters

Won't be long before you all have them. I already do and wonder what took so long.

As someone stated, you have to think long term

Ours, with installation, etc = $900

Quoted: I thought they used more electricity and more NG than standard water heaters?

They have to produce a lot more heat than standard water heaters, in order to bring the water instantly up to the desired temperature. So, some models have bigger burners or electric heating elements - and thus consume more power or NG while they're operating.

However, over the long run, they tend to use less electricity or NG, because their burners or heating elements only operate during the brief periods when a hot water faucet is actually open.

Tankless water heaters work on demand by using sensors and computer boards to monitor the flow of water and change the rate of firing to supply just the amount of hot water required for the current demand. (They are also called on demand heaters) This means that they burn less gas to supply hot water to something like a sink than they would if you are using multiple fixtures at the same time. This modulating firing rate also makes them very efficient to operate as you are only using the exact amount of fuel needed at that time.

A term that should be avoided is "instantaneous". Tankless water heaters are 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. This is not a big issue however. The problem is if a consumer thinks by hearing the term "instantaneous" that they will get water at every outlet in the house instantly if they get a tankless heater, they will be disappointed. Most homes have many feet of piping between the water heater and the outlets and do not have a recirculating system. The amount of time it takes from when a faucet or other hot water fixture opens to when the set point water gets to that point is called "Lag Time". In today’s large homes with low flow fixtures it is not uncommon to see a lag time of over 3 minutes to get hot water to remote fixtures in a home. Changing the type of water heater will not improve the speed of the delivery of water unless the location of the heater is altered or if a recirculating system is installed. Because of their small size of course, many times when a tankless heater replaces a tank, it can be moved to a more central location or nearer to the fixtures it is to serve. This may cut down on the lag time considerably

Tankless Water heaters save space in a home because they take up NO floor space. They also do not require protection from vehicles if installed in a garage and are so small they can be installed in a crawl space or attic as well. If you really need space, many can be installed outdoors giving you all of your interior space back. Just be sure to choose a model designed for outdoor installation and with freeze protection for your area. (More on this later)

Energy Savings of tankless water heaters:

Tankless water heaters save fuel because they do not have to maintain a supply of hot water in a tank and are typically "always off". Tank type heaters fire on and off all the time to maintain the temperature of water in the tank within about 10* of the thermostat setting. (This is called "Stand-by heat loss") This also can result in some noticeable temperature difference. Tankless water heaters provide hot water to the set point temperature plus or minus 2*.

Another thing that makes a tankless hot water heater more fuel-efficient is that they are "fully modulating". In other words they only use the fuel needed to heat the water to the set point at the current flow rate. If you are washing your hands using under 1 gallon per minute (GPM) you will be at a lower firing rate than you would be if you are filling your tub at 3 GPM. This works much like your car. When you are sitting still the car is idling. When you want to go or go faster, you give it more gas and when you get where you are going you turn it off. With their "always off" condition and their modulating capabilities it is common to see up to a 50% reduction in fuel use when changing from a tank type heater to a tankless unit.

If you are going to change from a 50-gallon gas heater to a tankless you are probably not going to realize quite that much energy savings. In fact a 50-gallon tank water heater does not use much more fuel at all compared to most tankless heaters. However a 50-gallon tank heater only can really give you about 40 gallons of hot water per use before you begin running out of hot water. The tankless heater will deliver more than 300 gallons per hour for most of the year and you can never run out! If it is an electric tank water that you are replacing, your savings may be higher than 50% depending on the size of the tank. If you really want to know what your savings may be, look for the yellow "Energy Guide" sticker on your existing heater and look for the one on the tankless unit you are considering. This will give you a good idea of what to expect. Of course your personal use will effect this as well. If you have a family of 6 that has never had enough hot water with a 50 gallon tank heater, your bill might just go up because now your family will not be taking cold showers or have to shorten them. If you have a vacation home that is occupied only on weekends or using the tankless for something like a school locker room, your savings will be greater because the tankless unit is "always off" eliminating a lot more stand-by heat losses.

Part of the decision making process is; What do you want? Endless hot water may be worth the additional investment to you even without an energy payback.


Location Location Location is so important with tankless water heaters:

Builders like the tankless water heaters for several reasons, not the least of which is space savings. When you charge by the square foot for a home, saving space means that home is worth more. A tank type heater installed in garage requires a floor stand, a pipe to protect against vehicle impact and normally venting all the way to the roof. In a two-story home, this means more framing, drywall and paint to enclose it. A tankless water heater is wall mounted and can be sidewall vented, keeping the cost of venting to a minimum. It also does not take up any of the garage floor space. Being able to install tankless heaters outside or build them into a wall gives even more options that the builder never had before. This means even less venting cost (practically none) and even more space savings. Some builders will locate them centrally in a crawl space to cut down on lag time. Others will locate them near a master bath or kitchen. Some will install them in attics or outside to free up more space. Since there is no tank to burst, installing a tankless heater in an attic is not as risky as installing a tank there. Even with a drain pan, a tank water heater in an attic is a catastrophe waiting to happen! A drain pan that is 3" deep will not do much good if the bottom blows out of a 50-gallon or larger tank water heater. (This is not an uncommon occurrence!)

On a large home, some builders will have two tankless water heaters systems. One will serve one part of the home and the other will serve the rest. This way the heaters can be located closer to the points of use and cut down on lag time without installing a recirculating system.

Outdoor Installation - tankless water heaters:

Many of the better tankless companies have models that can be installed outdoors. This frees up all of the interior space and does away with venting costs or combustion air issues. These units will have their own freeze prevention systems however you will need to protect your water piping from freezing. This can be done with a pipe cover kit or recessed wall box, which can be insulated. It is also recommended that you install self-regulating heating cable on the piping to keep it above freezing. Outdoor units require power at all times to operate their freeze prevention system. In the event of a power outage in freezing weather, you will need to prevent you tankless from freezing by leaving a faucet dripping or draining the unit until the power comes back on. A "back-up" power supply or generator is also an option.

Performance of tankless water heaters:

Another reason that builders like tankless water heaters is that they are able to provide hot water to todays popular large tubs. A standard bathtub holds about 35 gallons to the overflow. The popular soaking tubs hold anywhere from 45 gallons to over 80 and just filling up the tub leaves most without any hot water with a tank type heater for a period of time. A tankless can fill all the tubs of a home and then provide back to back showers, do the dishes, and wash the clothes. A tank type heater has to be very large to do all of these things without running out. We are only limited to the flow rate our tankless unit can provide. Choosing a tankless heater with the proper capacity for our house makes it possible to handle multiple hot water needs at once normally, without the worry of running out of hot water.

Until now, most people made "water rules" to determine who showers when, or when they could do the clothes or dishes. This goes away with a tankless water heater.

Some people mistakenly think that they will only be able to run one fixture at a time with tankless heater. While this may be true of the "Home Center" models, this is far from accurate when speaking about the professional grade heaters from Noritz, Rennai and Takagi. These models have the capacity to operate 3 showers or more at the same time! Some will correctly claim that tankless water heaters limit the flow rate to make sure you get the setpoint temperature and say that this means you will not be able to do multiple things within the home using hot water. This is simply not true. Choosing the right unit is important and will be discussed a little later, but making this claim is like comparing all tank water heaters to the old 30-gallon tank heaters that would run out after every use. Today’s tankless water heaters provide more than enough capacity to meet any hot water need from a one-bathroom house to a hotel. You just need to choose the correct system for your application just like any other hot water system.

Here is something else to consider when choosing your tankless heater. Asking it to operate three showers, the kitchen sink, the washing machine, the dishwasher and a laundry sink at the same time is not only unrealistic....your water pipes can’t carry that much water! Most homes only have a ¾" hot water main and most are now in PEX or CPVC materials. These piping system can not carry more than about 8 - 10 GPM total, including cold water. Also, many new homes typically see less than 2 GPM at a shower head due to pressure looses in the piping. In other words if you choose a tankless heater that can deliver between 6-8GPM in the warm months and 4+ GPM in the winter months you will be quite happy in a typical 3-1/2 bath or less home. You should avoid the tendency of some to oversize a tankless system based on unrealistic system demands. If in doubt, contact the manufacture for help.

Capacities of these water heaters have improved greatly over the first tankless models that showed up about 10 years ago in the US. The largest of these tankless companies, Noritz, has eight models currently available in the US that range from 6.3 GPM to the largest output model available in the world at 13.2GPM. Rennai models produce the same flow rates as the residential Noritz heaters and Takagi also has units in this range. Noritz even has commercial grade models that can produce up to 13.2 gallons per minute (752 gallons per hour from one unit!) Most of these products can be installed in multi-unit installations for high flow rate demands like luxury homes, large shower system with body sprays, locker rooms or hotels.

Many tankless water heaters are also installed with a remote control unit that makes it easy to change the set point temperature of the unit. One manufacturer, Noritz, has a standard remote that lets you set an alarm to the capacity of your tub. You then set the temperature you would like and fill with just the hot water. When the unit measures the gallons set an alarm sounds to remind you shut off the water. Another manufacturer, Rennai, is able to provide multiple remotes to serve the same heater to provide for multiple locations to change the temperature of the hot water if you like. (You still only get one water temperature at a time, you just have more location from which to choose the temperature.) These digital remote control panels also provide diagnostics for the water heater in the event that there is a problem. They flash a fault code to help service personnel find and fix any problems that may come up quickly.

The better tankless heaters by Noritz, Rennai and Takagi totally control outlet temperature so they can NOT be "overshot" giving you less than the set point temperature. You always get setpoint temperature plus or minus 1 or 2 * (Unlike a tank which is + or - about 10*) Electric units and home center models do not have this ability. I would advise avoiding the home center models completely as they lack the technology and BTU’s to give you good performance. In units that can not control their outlet flow, you will need to "throttle" the flow rate yourself at the outlet. This also means that if you are taking a shower and someone else turns on another fixture needing hot water, you may get a big surprise as the water temperature drops considerably in your shower!

Serviceability of tankless water heaters:

The better tankless heaters are very easy to work on. (I say the better ones because I have not had to work on a home center unit yet) Like anything else, training is preferred but any good contractor with a cell phone and a Philips screw driver should be able to take care of a problem using the tech support lines of the big 3 listed above. A manometer (Device used to measure gas pressure) is also a very handy tool to have.

How long do they last? About 20 years on average. Compare that to the 12-year average of tank heaters. This also contributes to the "total value" of the product since this means lower cost of ownership when factoring in replacement cost and life span of the product. Add in the long-term energy savings and your tankless heater just might pay for itself and in some cases it’s replacement!

Keep in mind however that installing these units outside in cold climates if there were a power outage, there is no freeze protection to these units until power is restored. You should protect the unit as detailed above. Most homeowner’s policies do not cover the water heaters themselves so it is a good idea to provide a generator in these installations or just put the unit indoors.
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Quoted: The simple facts about Tankless Water Heaters Won't be long before you all have them. I already do and wonder what took so long. As someone stated, you have to think long term Ours, with installation, etc = $900

Your water is already 70F+ out of the tap, they work much better the higher the water temp going into them. At 40-45F many struggle to bring the water up to the temp wanted by the customer unless flow is restricted.

BTU rating on gas one's tend to be in the neighborhood of 150K+BTUs to 250K thats 2 to 3 furnaces running at the same time figuring a 75K-80K BTU 90+ furnace.

Quoted: Quoted: Pros: -Constant hot water -Gets rid of the large tank -Energy efficient Cons: -Does not mix well with hard water. Meaning, if you have hard water then every six months you'll get so much mineral buildup the pipes will have to be removed and cleared. Soft water is fine though. dont forget 3x the cost of a standered water tank,.... kinda nagates the "saveings"

Did you figure in the taxcredit?

WOW!  Didn't expect this much info.  Thanks for the replies.  Looking at Rinnai so far.

Blake

We are in the process of building a new house and it was suggested that I get two tankless water heaters.  The house is 2500 square feet.  Not very big in my opinion.  We are going to pass due to the additional cost vs a traditional water heater.  If one could handle our needs I would have been getting one.  Oh well.  

Then again my plumber may not have a clue.  I'll have to do some more research.

Quoted: Quoted: The simple facts about Tankless Water Heaters Won't be long before you all have them. I already do and wonder what took so long... Your water is already 70F+ out of the tap, they work much better the higher the water temp going into them. At 40-45F many struggle to bring the water up to the temp wanted by the customer unless flow is restricted....

I live on a lake in NH, and pump my water directly out of the lake. It only goes through a sediment filter. My Toyotami is literally starting with ice water for months at a time. We've never had a problem with not enough hot water.