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ALPS 01-26-2007 03:20 AM

pros/cons for tankless water heater
I'm planning to replace the 40 gallon, 12-year-old,LP water heater that came with the house and want to learn more about the "tankless" type.

Aside from the obvious pro (endless hot water) and con (expense), what else should I consider? Plumbing, venting, gas supply are not concerns.

bethany14 01-26-2007 07:52 AM

Sizing is a concern, depending on your hot water demands. Here we only wash in cold water, and don't have a dishwasher, so our demand is minimal. However, if you do wash in hot water, and run a dishwasher, and then go hop in the see the dilemma. There are high demand systems available, though the price goes up considerably.

glennjanie 01-26-2007 11:44 AM

Hey Alps:
The pros are all there is to a tankless system, when properly sized. The higher cost will come back to you each month in lower gas bills because you are not trying to keep the whole 40 gallons hot all the time; vacation, sleeping, while you're at work and I could go on.
A new water saver shower head and faucets would help tremendously. If your faucets have the areator screen on them, they probably are water savers.

elementx440 01-26-2007 03:30 PM

i always heard on the am-radio improvement shows that you can get a tax writeoff for using the tankless systems, since they're more energy efficient, i would definately look into it...

shovelshort 02-18-2007 03:57 PM

I purchased a tankless water heater to replace an existing leaky tank water heater before I looked into the retro fit. I ended up selling the tankless to someone and buying another tank water heater.

There is a lot involved in retro-fitting for a tankless. Gas lines have to be a certain size, usually larger than existing. Venting is a big issue. Tankless heaters put out a lot of heat and exhaust. The vent has to be larger in diameter and double walled. The run can only be so long according to manufacturer which can be a problem in 2 story homes with the heater in the basement. You can vent out the side, but it has to be so many feet from a window.

If I were building a new home, I would definitely go with the tankless, but retro-fitting can be cost prohibitive when you are putting one in for utility savings in the first place.

ALPS 03-28-2007 10:11 PM

shovelshort-- good tips, this would be going into the basement.

Yes, a tax break is always good. I got a $360 tax credit(out of a possible $500) last week for the new windows and door.

And lastly, I've heard from a home inspector and a customer service rep at the local utility regarding the lower utility bill. It isn't always what it seems...

Sure, you don't have to keep 40 to 60 gallons of water hot 24 hours a day, but you do use nearly as much gas heating the cold water coming into your house. Heating large volumes of cold water in a short amount of time takes a lot of energy. Enough to off set your savings.

Maybe I could use the existing tank to hold the water so it could warm up to basement temperature before going into the tankless system?

ALPS 03-28-2007 10:13 PM


Originally Posted by shovelshort (Post 8187)
Gas lines have to be a certain size, usually larger than existing.

Proof that more fuel is consumed...

bethany14 03-31-2007 11:07 AM

Some highlights copied from:


Efficiency is higher than most tank type water heaters because standby losses are virtually eliminated. In addition, sealed combustion gas units have a higher fuel-burning efficiency than natural draft gas water heaters. PATH Field Evaluations have shown that energy usage can be decreased by 10 to 20 percent compared to a conventional water heater. Energy savings (as a percentage of total hot water energy use) are greater in homes that use less hot water energy.

Transitioning from the use of conventional water heaters to tankless systems can be difficult in an existing home. Electric heaters usually will need four times the electricity to operate. This will require additional wiring and possibly a higher capacity main electric panel. Many gas tankless manufacturers recommend a direct vent – this will bring in fresh air from outside for combustion and vent the flue gas using a blower through a side wall.

The installation costs of tankless water heaters are from 2 - 4 times higher than tank-type water heaters. For gas tankless hot water heaters, the same gas supply line and/or venting may need to be sized larger than for a typical gas tank. Electric tankless water heaters draw more power and will require multiple circuits and/or heavier cable, which will increase installation costs. Water connections for both are comparable or identical to those used on tank-type water heaters. In some cases, the temperature and pressure (T&P) valve necessary for tank systems may not be required for a tankless heater. (Check with your local code official)

Gas and electric whole-house tankless water heaters are more expensive than typical tank systems except when comparing to high efficiency tank systems. In these cases, the high efficiency tanks may be close in cost to the tankless systems.

Electric tankless water heaters generally cost 10-20% ($40 - $80/yr) less to operate than comparable tank-type water heaters. Gas savings may be about 20 -40% ($50-$100/yr). Equipment life may be longer than tank-type heaters because they are less subject to corrosion. Expected life of tankless water heaters is 20 years, compared with between 10 and 15 years for tank-type water heaters.

Square Eye 03-31-2007 07:33 PM

Not enough benefit to convince me that I need one.
An electric water heater can be set on a timer that turns it off during off-peak usage hours. But in my home, there is no real off-peak time. Starting the cycle over again , warming a cooled water tank may offset the savings anyway. I have a gas water heater, recovery times are very quick. Combine that with the fact that the demand for hot water in my home may come at any time, eh, I'll insulate my tank and keep it.

bethany14 04-03-2007 07:27 AM

Another con,
A friend of mine is building for himself in a very small town in Eastern MD. When he got permitting for his tankless they were very apprehensive toward the 'new' technology--they went as far as insisting he needed a pan under the unit, as for a tank. After much debate, they finally realized there was no need for it, but it was quite the frustrating struggle for him.

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