Tank-less Water heater Vs. Traditional Water Heater

RatLabGuy said:
Edited to reflect that there are people in the world that actually have a need to conserve water too.
But even that depends on teh setup.
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A fractional hp recirc pump that consumes a whopping $8 of energy a year will stop with consumption. But few feel THEY NEED that
 
shawn said:
Depends on how you measure capacity.

I'd say a 75 gallon gas water heater can provide more HW than any single family residence could ever use. You're looking at probably 120-130 first-hour gallons based on a 120F setpoint. Increase the setpoint and maybe add a mixing valve, and you're easily up in the 200-250 gallons first hour range.
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No mixing valve but we keep ours at "A", it's something like 130-135.... "don't touch it too long" hot, with a normal old 40 gal gas WH.
And the only I time I can remember running out was with two shower and washer going at once. We run out of pressure before we run our of HW. Consecutive showers never do it.
 
CasterTroy said:
A fractional hp recirc pump that consumes a whopping $8 of energy a year will stop with consumption. But few feel THEY NEED that
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My water coms free from the ground and there's plenty of it... I'm of the opinion that the constant lesson in pateince carries its own virtue.
 
RatLabGuy said:
My water coms free from the ground and there's plenty of it... I'm of the opinion that the constant lesson in pateince carries its own virtue.
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What makes you think a tankless saves water?
 
shawn said:
What makes you think a tankless saves water?
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I didn't say I think it saves water :flipoff2: .
But the sales pitch is that [when used at the POS] you have instant hot water instead of letting it just run down the drain while waiting for it to get hot.
 
shawn said:
Electricity is an expensive way to make hot water.
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Thanks.
And yea I get the premise. On the flip side...With below grade basement the electric WH didnt require a penetration for a new gas line. So for me it was gas tankless outside vs electric tanked indoor. We went outdoor tankless and have been pleased. Just didnt know if there was a recovery time difference gas vs electric. It wasnt uncommon to run low on hot water with the electric 80Gal tanked even with thermos turned up.
With the gas tankless its never been an issue
 
RatLabGuy said:
I didn't say I think it saves water :flipoff2: .
But the sales pitch is that [when used at the POS] you have instant hot water instead of letting it just run down the drain while waiting for it to get hot.
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Except for the part where you said it was designed to save water.
 
shawn said:
Except for the part where you said it was designed to save water.
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Except that I did not actually say that. You just inferred I did.
 
shawn said:
Yes, because electric coils are inefficient
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Again, I get the efficiency part.

I'm genuinely attempting to converse and learn not trying to argue for e-cred. Im not sure if you are intentionally being vague for some reason or if its just a poor communication style.

To re-state. I understand electric to be less efficient. That isnt the question. The question is if the recovery time is slower. Just because its a less efficient methid than fire! fire! yeah! (in my best Beavis voice) doesnt mean necessarily that its slower. If standard design used a higher wattage element then in theory it recover in the same amount of time, or even faster, just require more energy input to achieve the result.

So my question isnt one of efficiency but more one of what is standard design
 
Ron said:
Again, I get the efficiency part.

I'm genuinely attempting to converse and learn not trying to argue for e-cred. Im not sure if you are intentionally being vague for some reason or if its just a poor communication style.

To re-state. I understand electric to be less efficient. That isnt the question. The question is if the recovery time is slower. Just because its a less efficient methid than fire! fire! yeah! (in my best Beavis voice) doesnt mean necessarily that its slower. If standard design used a higher wattage element then in theory it recover in the same amount of time, or even faster, just require more energy input to achieve the result.

So my question isnt one of efficiency but more one of what is standard design
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He's just a shitty communicator.
The answer is yes, recovery time is slower because of physics. Heat transfer from the gas combustion is greater because there is more surface area getting hot and it is hotter [I think, although a direct BTU comparison could be made]. Electric has only the 1 or 2 small rods.
On top of that the time to heat up is much longer. From the moment the thermostat says "GO!" the electric coils take longer to reach the same energy output. If your hot water is draining out at the same rate in both cases, that means by the time you have reach equal temp of the coils, the electric has net colder water that it has to heat up.
Efficiency in energy transfer is functionally measured in time as much as it is magnitude.

EDIT - by the way, it would make a hella lot more sense for water heaters to be measured in calories, because then it would transfer evenly across ebergy sources. But nobody wants to think like that.
 
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RatLabGuy said:
Except that I did not actually say that. You just inferred I did.
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Sure.
 
RatLabGuy said:
Heat transfer from the gas combustion is greater because there is more surface area getting hot and it is hotter [I think, although a direct BTU comparison could be made]. Electric has only the 1 or 2 small rods.
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I think we've been overlooking another factor, too - with gas, there's just more energy available. Getting back to your point about thermodynamics, gas systems are losing some energy to exhaust heat, but there's so much more energy available to start with that it doesn't matter. If you try and do instant hot with electric, you need something like 24,000 watts just to get 2.5gpm. To get a usable system for a typical house, that might mean 200a just dedicated to making hot water. Meanwhile, it's nothing to get a few hundred thousand BTU out of your gas line.
 
You guys are really ignoring solar. Spray water from a black hose thats been sitting outside on a summer day, and it's instantly hot, and uses zero man made energy. I mentioned it earlier in the thread but I guess you planet haters were too busy arguing about your fossil fuel energy. :flipoff2:
jeepinmatt said:
How much solar hot water does it take to turn a straw man in to a red herring using ad hominem without confirmation bias?
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jeepinmatt said:
You guys are really ignoring solar. Spray water from a black hose thats been sitting outside on a summer day, and it's instantly hot, and uses zero man made energy. I mentioned it earlier in the thread but I guess you planet haters were too busy arguing about your fossil fuel energy. :flipoff2:
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I had a friend in Kernersville years ago that bought a house that came wit ha shed that somebody had mounted a huge black tank that was wide and flat to. He assumed it was for this purpose, Free hot water from the sun.
The problem is it's only useful in the afternoon. And when the weather is nice.
The same thermodynamics that make a metal box heat up nicely in the sun also allow it to cool quickly once the sun is gone.
 
RatLabGuy said:
The problem is it's only useful in the afternoon. And when the weather is nice.
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I did an internship (see also free labor using HS kids) with J. Aubrey Kirby architect... Well he called himself a SOLARtect back when I was a senior and taking Architecture at the career center in HS
Everything he did was based on solar and using all natural light. He broke out in 1980 back after the fuel crisis when everyone was looking for alternatives to electric, fuel oil..etc..before natural gas was really piped to every neighborhood.

Problem is.. in NC you have less than 115 useful days for solar.
Needless to say he closed his doors in the 90s as NG became stupid cheap

Davidson county schools wanted to go green with a middle school back in 2010. It had 3 classroom wings and the school board wanted to test a theory one of the board members had (former ME)
Each wing would have separate water heaters.
1 wing electric
1 wing heat pump water heater
1 wing solar
This.. in addition to the GAS main water heaters for the kitchen.

Thinking of ahead I sized a HW loop to extend to the opening of every wing, with taps, valves, and caps
Once the warranty expired maintenance went in and piped the wings to the gas HW loop because HP heater never functioned correctly and the solar one was running on electric backup 90% of the time. And it and the electric wing were costing them boatloads in energy
 
shawn said:
I think we've been overlooking another factor, too - with gas, there's just more energy available. Getting back to your point about thermodynamics, gas systems are losing some energy to exhaust heat, but there's so much more energy available to start with that it doesn't matter. If you try and do instant hot with electric, you need something like 24,000 watts just to get 2.5gpm. To get a usable system for a typical house, that might mean 200a just dedicated to making hot water. Meanwhile, it's nothing to get a few hundred thousand BTU out of your gas line.
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If talking tanked WH, I know gas will have more energy and efficiency, but how does propane alter the cost? NG is cheap and comparative to electric for many things, but propane being higher seems to tip the scales back to electric. Are tanked WHs the same way?
 
jeepinmatt said:
You guys are really ignoring solar. Spray water from a black hose thats been sitting outside on a summer day, and it's instantly hot, and uses zero man made energy. I mentioned it earlier in the thread but I guess you planet haters were too busy arguing about your fossil fuel energy. :flipoff2:
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They had this setup in middle eastern country I spent time in. Black pipes across the roof. It would melt your skin off for 8 seconds and then turn to glacier water.
 
Wes said:
They had this setup in middle eastern country I spent time in. Black pipes across the roof. It would melt your skin off for 8 seconds and then turn to glacier water.
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We had it at scout camp back in the 90s. Leaders raved about it.
 
200ish gallon combined electric wh. 9 solar water panels (which work well even in WNC) on a 700+gal tank which runs through a gas wh converted into a heat exchanger and also feeds radiant flooring. And now a supplemental on demand gas system servicing the 'warehouse' side. Having experienced these all, besides capacity limits, with regard to one of the comments earlier. Unless the hot water lines are plumbed for circulation, they all equally take time to deliver the hot water to you to clear the lines/hoses until it reaches you.
 
I have been trying to figure out the best water heater to put in a detached garage. I want to be able to wash my hands and the occasional tool or part with hot water. But I could also go days or weeks without needing hot water. The small tanked heaters are similar in price to a 3 gpm tankless. I hate to think about keeping a tank hot with electricity or burning fuel to keep the pilot on for days at a time. If I could think about it maybe I could throw the switch on a tank unit when I know I will be there on the weekends.

Aside from the cost of the unit and the cost of running #6 wire across the shop, is there a downside to tankless in this application?
 
thecj3man said:
I have been trying to figure out the best water heater to put in a detached garage. I want to be able to wash my hands and the occasional tool or part with hot water. But I could also go days or weeks without needing hot water. The small tanked heaters are similar in price to a 3 gpm tankless. I hate to think about keeping a tank hot with electricity or burning fuel to keep the pilot on for days at a time. If I could think about it maybe I could throw the switch on a tank unit when I know I will be there on the weekends.

Aside from the cost of the unit and the cost of running #6 wire across the shop, is there a downside to tankless in this application?
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You just need one of those instant under sink hw heaters.
 
Learned something on this topic recently don't forget your permit....

I had no idea how much shit NC requires you to take Permits for. Water heaters are one of them technically. Unless work is performed by a certified installer. you need a permit to change a damn water heater in NC... :laughing:

Apparently,
I have committed many..... many.... code violations.
 
DonYukon said:
I have committed many..... many.... code violations.
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Me too LOL
If I called down to Dobson and asked about a WH permit, I’d probably be told to just put the damn thing in. This ain’t Cary up here.




I have mentioned that I like watching This Old House and Ask This Old House on the Roku. They have a segment called Future House that showcases new ways of building for efficiency and “green” concepts.

They are talking more and more about heat pump based hot water (geothermal and air based) and keep using the phrase “for every dollar you put in, you get 3 dollars of heat”. Now I am a firm believer in high efficiency heat pumps and they are a very cost effective way to heat and cool. This interests me because moving heat is much cheaper than creating it.
 
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