Hello S:

Poaaibly ef for tankless.
Correct size (and OEM will mention when you callthem) Gas lines sized  to MBTUh are as you thought, very important.
A low budget 150 MBTUh unit @ under 2000 installed (by a 'friend' of aGeoThermal customer on existeing natural gas), not producing over 3.6 GPM at a 60F rise from 52F well water, runs poorly on a 1" gas line. Pressures could have been tested, etc. AN additional tank not used as an electric, was for from the GT (originally desuperheateted, small HW GT generator, not Priority) - NOW is just buffer to raise to 90F LIMITED  is as a loss all around, rather than just the right design at first... the instant gas HW required a 35-degF potential rise to work on raising water to 125, as programmed.

A Q or 2)

Now mentioning radiant heat, how much , sq ft etc ?
and considering more of  all the accounting about other possible HW heating with DeHumidification, not robbing the home of heat in the winter, etc., do you owe taxes for to qualify for other ideas?

is solar completely out?
is a very small Priority -HW -Heat-Recovery (reclaiming in COOLING modes ) GeoThermal System out ? Could you get from a 3000-4000 install to be a net 5000, for superior savings added to any radiant and heating HW and dehumidification and controlled cooling and forced air controlled/distributed -better GT HtPump ultra ef HVAC-HW-Reclaim-DeHumidification?

Added to radiant and a new HW tank you may want to multiply by 70% of all installed and or contractor costs systemically; and see what local Ut'y rebates may support.

A loop can be installed initially at barely the size of the unit (1.1/2 to 2.1/2 tons) with a 43" wide x 34"h  x 13" off wall , floor mounted and very quiet GT-Console, double wall Cu NI heat-exchanger,  DIY or contractor, if required.
 
Short of a mini-GT split coil added to an existing HV furnace, that , or a Console, may also provide an exchange for a small back yard pool heating, too: --- NASA Engineer picked up, tied into buffering tank for Domestic-HW (DHW) and heats his pool, leaving the windows open in the home to 'warm up'  in the summer.

Local loops and installs should be considerably a best 4-to 5yr ROI. ?  Do you have a well?
What is the total picture of resources vs needs , from just doing a 3000- 4000 dollar thing, to lifestyle and building and radiant and cooling/Dehumidification, within a budgetary envelope of satisfaction.

YOUR LOCAL installed "costs" may be better-balanced with a 5 year plan, maintenance, replacements in 10 years with ROI's written against "just adding a HW tank". (pulling the "lttle radiant" trigger) 

If you want mid efficiency (80-88%) then tankless gas is the way to go and if you want high efficiency then the Navien tankless is around 96% or the Polaris water heater (tank type, 95%) is probably 3600+

My informal sources for HP water heaters (new GE type) is that they will probably have a 5-7 year lifespan. Otherwise, what you hear about them seems correct but remember that while they remove humidity in the summer they do not cool.

Posted By Sav on 02 Jun 2012 07:28 PM
Dear friend, in my area and I am sure it's similar everywhere, the energy contained in gas is 4 times compared to electric for each dollar. In other words, it costs 4x as much to heat water with electricity compared to natural gas! A no brainer! No matter how cheap electricity seems don't go for it. One more thing: the U.S. is probably the only country where the majority doesn't have a tankless heater or a solar water heater. It's absurd if you ask me. Travel to Europe or even China. Everyone heats water with sunlight for FREE. I read CHINA is the leader in solar. CHINA!!! It's CHINA can you believe this. I saw a video once how they build water heaters for less than $20 in Brazil out of TRASH and they put it on their home and it works for years! Why is it that we are so far behind? I blame several things: * georgraphical isolation from the rest of the world. That's really a problem you know. If China was a road trip from here, we would be inspired to try one of their water heaters, too. * political isolation from the rest of the world. We will never hear about some other country pushing green tech because cable, CNN and FOX are owned by a handful of rich people * even simple things as TV aren't really giving you an accurate picture of what's going on in the world, it's all manipulated by corporate giants who don't want you to know nothing. The ideology "buyer beware" has been driven to its purest form! If you don't know better, your fault! And the government doesn't seam to do much to change this either. I saw a video of guy installing solar water heaters in Antarctica, so there's no excuse really. The water came out boiling hot! I asked my plumber hey what does it cost to do tankless, vented, solar, etc. Finding affordable solar appears to be a problem in my area. For all other options we get seriously ripped out (DC metro). Like $1,200 for a 80% power vented 50gallon heater. I am like, dude for that money in Europe you can get a solar heater with an electric backup for cold days! I would go for a cheap gas tankless if gas is the choice. If it breaks, trash it and buy another (not a green way to do things however). Tankless may require a new gas counter or whatever you call it since they pull a lot of gas in bursts. If you don't go tankless, get a gas heater with electronic timer control so you can switch it off entirely at night time. I like forums like this one, they are an eye opener to me: hey there's a lot of S***T out there your plumber/roofer/builder/neighbor/etc doesn't know about OR doesn't want *you* to know about. The internet is clearly changing things.

Sav,

I have worked in manufacturing plants of various products over the years.  There are several points you should take into account about these "large corporations" that are holding us back.

1.  They either manufacture a global product, or they manufacture a porduct that is at least applicable to the Western Hemisphere.  This is a reality of business.

2.  Probably every water heater you can buy meets the vast majority of codes and jurisidictional requirements in every jurisdiction it is sold in, i.e. one size fits all.  That big coporation has to hire an army of engineers and product specialists just to be able to do that, plus, it has to keep up with all of the regional changes in those rules, and that is just in the United States.  Most manufacturers are selling their product througout the Western Hemishpere, but certainly in the US, Mexico, and Canada.  Some jurisdictions have hurricane codes, some have earthquake codes; some prohibit urethane insulations in certain products, others don't, some have all kinds of monoxide detection and flame safety requirements whereas others might have completely different venting requirements.  In most US jurisdictions, you probably can't install a device without a UL or CUSA label, you certainly can't buy one without it at Lowes or Home Depot.  Your $20 Chinese water heater is never going to meet these requirements.  If you built a water heater out of garbage, like the Brazilians, you probably couldn't get FHA financing on that house if you were reselling it until that water heater was removed.

Think about it: 50 states with at least 35 counties or parishes each, several cities in each county, many, many variations in local building codes, which brings us to .....

3.  Litigation.  That big corporation also employs an army of lawyers.  Do you know what happens when a building burns down?  The insurance company covering that buiding sues every manufacturer that had electrical product inside of that building, regardless of what started the fire.  I know.  I had to do supporting work for one of my previous employers legal defense at times (I am an engineer).  Two I was directly involved with was a lawsuit by an insurance company after a building was burgularized and burned.  The fire marshal ruled it was arson, but my employer was sued by the insurance company of that building because their "experts" decided it was faulty wiring inside an assembly we bought from someone else and incorporated into our product (all UL labeled, or course).  In another instance, we were sued because an employee of a construction company dropped one of our products on another employee. 

This is the reality of business in the US, and it's reflected in the cost of everything you buy, but more importantly, it is a very real contributing factor to the reluctance of manufacturers to invest in alternative technologies.

4.  Profits.  Yes, us Capitalist Pigs don't do anything unless it puts money in our pockets.  The bottom line is that most of the profit opportunity for most solar water heating systems is on the installation and design side.  The individual components are not that much different than standard product.  A solar water storage tank, for instance, looks an awful lot like a standard electric water heater.  The difference is that it is installed with pumps and piping and control systems and solar collectors, and sometimes heat exchangers and circulating pumps.  Most of those components are selected based on the myriad differences of each individual installation.  It would be very difficult for a water heater company to produce a "one size fits all" and completely self contained solar water heater.  It is rather easy to make a one size fits all and completely self contained electric or gas water heater. So for our big corporation, something like 90% of the profit opportunity for it is in the water heater tank itself.  They have no existing business model for the part that Mike Solar* does, and in reality don't want to go there.

So, it boils down to the fact that it seems impossible for that big corporation to produce a unitized and standard design solar water heater that they can sell in the same manner with the same profit margins as a conventional water heater. 

5.  My tankless Rinnai is absolutely wonderful.  It cost about a third the cost to operate as the old gas tank water heater it replaced, but even if it didn't, I NEVER run out of hot water now....and even though it cost so much to retrofit it (in place of an existing gas tank type) that is doesn't have a pay back...I would do it again tomorrow.

6.  In my climate, a simple tempering tank in an unvented attic will probably give me 60% of the benefits of solar water heating at probably 10% of the cost....at least 50% of the time...but...I hate vented attics, so I'm not going to do it....see #5 above...

*Note to Mike Solar:  I said that's were the profit opportunity is, not that you'd actually realize it.

Posted By strategery on 02 Jun 2012 02:38 AM
Would it make much a difference if my hot water needs are limited to showers and the dishwasher? We wash all our clothes in cold water. Our handwashing is done with cold water. Wouldn't that make the condensing tankless a better option for me because the ef would be about to what they state plus I wouldn't have the standby losses associated with tanks?

What do you think of tankless units with internal buffer tanks? Or "hybrid" tanks like the eternal or the one by AO smith? About the same price as the Vertex I know, but does it solve a lot of the problems with tankless? Does it still require a bigger gas line?

The standby loss of a condensing tank is quite small- about the same as with electric tanks. This is in contrast to the standby losses of atmospheric-drafted  type gas fired tanks, where the center-flue heat exchanger constantly convects heat out of the tank 24/365.

Posted By strategery on 04 Jun 2012 06:56 PM

The standby loss of a condensing tank is quite small- about the same as with electric tanks. This is in contrast to the standby losses of atmospheric-drafted  type gas fired tanks, where the center-flue heat exchanger constantly convects heat out of the tank 24/365.

I wonder why this is? I think I understand how the Vertex condensing unit works. It has a really long coiled heat run that distributes the heat more evenly? But since it USES more of the heat it gets by burning natural gas, wouldn't it also only need to run for a very short period of time causing some lowered efficiency? I'm just thinking about the unit keeping the water at the desired temperature for the 10 hours or more where no hot water is being drawn, but SOME standby loss is occurring? I could imagine that this would need to kick on once or twice a day to keep the water at the set temperature.

BTW, we have programmable thermostats for our hvac systems because it saves money not to heat or cool an unoccupied space. Why don't we have these for water heaters? It seems like a no-brainer that we should have more control over the arguably the most expensive appliance in the home. Just curious.

Interesting about the Navien CR with its buffer tank and its real performance. They recalled this unit due to a bunch of problems and it's been replaced with a similar one called the NR. I wonder if it wouldn't have been better to test a few different condensing tankless units (such as the eternal, or one of rinnai's) just to be sure that they're not testing a particularly bad unit that spoils the entire category?

Dana, do you think a condensing tankless with a well-insulated 1 or 2 gallon electric water heater in front of it to help buffer and eliminate cold water sandwiching would work to resolve the issues with tankless?

I put in a lot of the CR models a few years ago and regret it. It didn't have anything to do with the buffer tank but with the flow sensor and sometimes the main board. I would say that i have been back to 40% of the installs to change something and while Navien has been good with the parts, I cannot get them under warranty without standing in front of the unit, giving them the model and serial number and going through a series of tests, most of which allow us to reach the same conclusion. Send the same parts.

While it is a PITA, and i have to make a minimum of 2 service calls, Navien gets direct knowledge of the issues with the units and I believe this has resulted in the NR model, which, has not had any problems in my installs (fingers crossed). I now carry spares for the older units as I know I will be seeing the customers again.

I am definitely not throwing the baby out with the bath water here as I like the build quality of the Navien better than the Rinnai or Takagi etc, and for me its ability to take solar preheated water is important and temp fluctuations with most units under these conditions have caused lots of complaints. That said, many of my customers now turn off their tankless from May to Oct so I wouldn't hear from them anyway.

a condensing tankless with a well-insulated 1 or 2 gallon electric water heater in front of it