Converting from domestic (tank) to tankless water heater

Page 2 of 2  
I used to use 26-30 a month for Ng for cooking, HW and dryer in summer with a tank, now I use 6$ Ng a month in summer, cooking and dryer use have not changed, standby loss and heating 40 gallons cost is greater than you think.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
m Ransley wrote:

A comparison chart on the Bosch site:
http://www.boschhotwater.com/StartPage/BoschHotWatercomHome/GasProducts/AquaStar125Series/EnergySavingsChart/tabid/349/Default.aspx
Shows a pretty large difference between tank and tankless for gas water heaters.
For the electric however:
http://www.boschhotwater.com/StartPage/BoschHotWatercomHome/ElectricProducts/PowerStarAE115AE125/EnergySavingsChart/tabid/399/Default.aspx
There is very little difference. It would appear that stack losses from the tank type gas heater are the largest factor. Heating a large volume of water isn't an issue when you can insulate it well as in the electric models.
Pete C.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
But is there realy enough insulation on any tank, maybe 2" of foam for say R 12, but code for attics in my area is R35 and optimal is R60. Loss also continualy occurs through the water pipes, you are keeping water hot, there is alot of loss.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
m Ransley wrote:

Based on the comparison for tank type electric and tankless electric where there was clearly little standby loss from the heated tank I'd say yes.
Newer heaters have little valves that are designed to limit heat loss to the pipes in standby. Certainly insulating the hot water pipes is still a good idea.
Pete C.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Pete C. wrote:

Losses in pipes are NOT a part of the Bosch comparison. Yes, we must recognize them as they will extend our use of hot water while we wait for the pipe to heat back up (or we use a recirculation pump).
The Bosch comparision said that electric tankless was a infinite payback at 50 gallons and a near infinite payback at 80 gallons.
Yes, stack losses and insulation losses are the dominant factors in energy use difference between tank and tankless gas heaters. In this case, gas tankless makes a large enough difference to perhaps get a positive payback in 5-7 years.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Model Energy Factor Cost to Operate* Annual Savings Annual Savings 250SX/SXO 0.85 $250 $110 $151 125B/BS 0.69 $308 $52 $93 125HX 0.80 $266 $95 $135 125FX 0.78 $273 $88 $129 40-gallon tank 0.59 $361 75-gallon tank 0.53 $410
Note the stated savings. In the winter the extra gas used helps heat your home If the heating season lasts 6 months then divide the savings by ONE HALF.
Now the largest savings bosch lists is $153 divide by 2 it saves about 76 bucks a year. Thats nice BUT the install costs several times the cost of a standard tank.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thats ridiculous that the extra gas heats a home with a tank, exactly the oposite will happen with an open flue to a chimney, its called draft. Savings, at what price a therm, certainly not what is charged now. Look hallerb you can run your numbers any way you wish to make yourself feel better you don`t own one, but I have proof of a 4yr payback, my utility bills. You need to talk to owners of Ng tankless.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
" snipped-for-privacy@aol.com" wrote:

The heat from the extra gas used mostly goes up the chimney, not into your home since it's mostly stack losses, not losses through the exterior of the heater. What heat does get out into your home may assist in heating it in the winter, but it also hurts when air conditioning in the summer.
Pete C.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@aol.com wrote:

Tank type Gas water heaters are not allowed, by building code, in many locations to be inside the heated/cooled space. Tankless can be, if combustion air is brought in.
So energy losses by a gas tank type water heater do not add to building heat, not always.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.