Tankless Hot water syatem?

Hello,
I just had a person that rates houses for energy efficiency come and rate our house. One of his suggestions he made was to pull out my existing Gas fired hot water tank and install a Tankless hot water heating system. We don't have a family living here only my wife and I and we're both away through the day working .....so the hot water demand is only morning and evenings. It makes sense when he explains it. He says "why have a large tank down there heating water 24/7 when your demand is about an hour a day?" Are there any disadvantages to this tankless system? Does anybody here have one that would care to comment? Thanks.. Jim
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Some people love them, some hate them. Nothing is perfect and nothing is worthless. However, before condeming tank water heaters, your "consultant" should have explained the difference between an old style low efficiency tank heater that you probably have, and a high efficiency tank heater and those inbetween. High efficiency water heaters just sip the gas and can supply continuous hot water similar to a tankless yet still have the reserve of a tank of hot water available.
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Your existing tank isn't heating the water 24/7. It heats it to the set point, then turns off. The tank is pretty well insulated and will hold the heat fairly well. The heater only kick on for short periods to maintain the set point. The tankless method requires lots of energy for the period when hot water is being used, then sits idle. There is probably some savings, but I doubt it's huge

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wrote:

About the only way to really make this hit home is the hard way. Go to your water heater and sit there for 24 hrs. Watch how much it DOESNT run! Then call the guy back up that came to give you this so called house efficiency rating and call him the uninformed hack he is. Nothing wrong with tankless but if you are purchasing one to save money by increasing efficiency you have to understand the whole picture. Bubba
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Actually because you have such low usage, it will take you all that much longer to recoup the cost. I would think high usage would make a better argument for spending the money on a tankless system by replacing a perfectly good tank prematurely. At least I'd wait until you HAVE to replace the current tank (at 11 year point depending on your water corrosiveness). Then at least you can subtract a new tank cost from the new tankless cost and start your recouping from there.
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My water heater died about a month ago and I took a quick look at tankless before I bought a new gas tank style.
If you and the wife only take showers and your winter ground temp is warm then you might break-even on the extra cost in 10 years.
If your winter ground temps are low you should really study the temp rise factor. How much a tankless system can raise the incoming water temp.
They work for some people and they don't for others. I prefer clean dishes from the dishwasher and a Jacuzzi full of hot water for my aching back in the cooler months.
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when they go bad. especially if it is an old house with the tank already installed. If you are in an area that looses power, the small 5 KW class generator will heat the water in a tank.
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A well insulated tank has minimal loss over the course of a day. Do you hear it turn on often when water is not used? Probably not. Some tanks will only drop 6 to 10 degrees in a day, using little energy to maintain a reservoir of heated water. In the case of heating season, there is no loss if you are heating that portion of the house anyway. So, your have to figure payback on only six months a year.
Price out one of the tankless models and the cost of installation. Then you will think that what he says makes little, if any, sense. Then go enjoy a nice beverage knowing that you are really rather efficient and cost effective with what you have.
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The thing about a typical gas water heater is that it has a chimney going up the middle of the tank, which is obviously not insulated because it is part of the heat transfer path when the burner is running. So you get significantly more standby losses from a gas water heater tank than from an electric water heater tank.
For example, with an 80% efficient burner, a gas water heater will have an Energy Factor (which includes the standby losses) of 0.60-0.65. So the standby losses are 15%-20%. By comparison an electric tank water heater can have an energy factor of over 0.95, so the standby losses are less than 5%.
Cheers, Wayne
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Jimi wrote:

Afew friends who had one installed went back to old tanks in frustration.
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Jimi wrote:

Disadvantage? yes, you'll never get 140 degree water out of it for your dishwasher. and they cost a fortune.
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I'd say one big disadvantage would be that you may never come out ahead financially. I have a typical gas water heater, not high efficiency, and in the summer, when it's the only gas load, my bill is less than $20. And that includes actual water usage as well as the standby losses, which obviously aren't very substantial..
You may also find that to get the right size tankless requires a larger gas service, increasing gas pipe size from the meter to where the tnakless is located, etc.
If you can, do a simple experiment sometime. When you're going to be away for a few days to a week, record the gas meter reading, make sure the water heater is the only usage, ie turn off any other pilot lights, heat, etc., then read it again when you return. That will tell you how much you are paying for standby losses.
And as others have pointed out, these losses can be cut down substantially by going to a high eff gas tank water heater, which is still typically a lot less than the install of a tankless. These close off the exhaust vent when the burner is not running, which substantially cuts the heat loss. I'd be looking at those when it's time for a new water heater. However, one other thing to consider is there is currently an energy tax credit in effect and some of these solutions could get you a credit for up to 30% of the cost. If you have a tank that is nearing the end of it's life, now may be the time to replace it with something.
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There are tankless designed to do 180 all day long, but what a waste it is to heat a tank to 140 just for dishes. My dishwasher has a preheater and I would never buy one without. An AO Vertex or Cyclone is also expensive, saving energy is an investment and it costs money.
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Yes, I don't see why you can't get 140F water out of a tankless. They are spec'd for a given temp rise. All you need to do is figure out your incoming lowest water temp and what flow rate you want to support to size the unit. I have my tank set at about 130 and the dishwasher works fine.
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snipped-for-privacy@optonline.net wrote:

Yes, they have a certain temp rise capability. And it ain't a hundred degrees. The incoming water in our area in the winter is about 38 degrees. Heat that with a tankless and it'll dribble like an old man with an enlarged prostate.
s
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Please, I'm trying to eat my breakfast.
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Oh really, I heat 35-36 incomming to a hot shower without even my little 117000 Btu Bosch on high. I used 3/4" gas line for a 6 ft run and did a Manometer test in winter, because I know in winter pressure drops with high demand at -15f -20f. And I will bet anything, of the the units you complain about you never tested gas flow with a Manometer when water was 38f with all the homes competing gas apliances on. Its a fact in my area even mains flow pressure is reduced on the coldest days up to 20 %. As far as temp, there are Tankless designed to run radiators to 180f. You complain about tankless, but I bet you never tested gas flow in winter. There are im sure many jobs where they cant be put in and get 100% output because of meter or main issues.
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