# ondemand hot water heater



## jimcope (Sep 3, 2008)

Hi 
 does any one know what is cheaper to run gas or eletric ondemand hot water heater I heat with propane now in a tank. 
Jim


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## d.n.f. (Sep 3, 2008)

Manufacturer's list consumption.  You are going to have to price out your costs for electric and propane (or natty) and do the math.

I found natty gas was the way to go but I was getting cheapish gas at the time.


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## Sandor (Sep 6, 2008)

Demand electric water heaters need like two 40amp 220v circuits to feed it. That will spin the meter!

Gas will be cheaper, as long as its available!


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## rhetoric (Sep 9, 2008)

I'm nervous about a source water heater w/ our hard water.  Not sure why I think it might be worse than a tank.  Anybody know?  We have a softener, but...


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## fraxinus (Sep 9, 2008)

Re on demand heaters in general: A recent issue of Consumer Reports concluded that while they work efficiently, the payback period is very long - perhaps longer than the likely life of the heater. They also consume more energy in colder climates because the incoming water temperature is lower. Hard water and other water quality issues also negatively effect them.


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## PaulRicklefs (Sep 25, 2008)

fraxinus said:
			
		

> Re on demand heaters in general: A recent issue of Consumer Reports concluded that while they work efficiently, the payback period is very long - perhaps longer than the likely life of the heater. They also consume more energy in colder climates because the incoming water temperature is lower. Hard water and other water quality issues also negatively effect them.



All water heaters use more energy which the incoming water is lower.  Tankless water heaters actually shine with low incoming temps as they do not suffer the same kind of flue gas condensation issues as standard gas tank-type water heaters.  Hard water is a legitimate issue as the smaller heat exchanger surfaces are more prone to clogging, but the swift flow of water over the exchanger generally keeps them clog free.  If there is a significantly large amount of diluted minerals in your water it is suggested to treat the incoming water regardless of water heating means.  It will extend the life of any water heater.

In the winter my incoming water temps settle at 40 deg F.  Most people in the area do not use gas-fired tank type water heaters as they do not last longer than 5 years on average.  The thermal shock causes flue gas to condense on the burner-side of the heat exchanger causing corrosion.  This simply does not happen on a tankless.  If you have a low incoming temp and want to keep your heater for 10+ years I recommend to either use a huge tank (eg. 60+ gallon, electric tank, preheat the incoming water (with an uninsulated tank) or go tankless.


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