Are "On-Demand" water heaters a good Idea?

I put in a Rinnai system when we converted over to gas two years ago. The costs for fuel savings have been a mix of the lesser cost for propane and the "on demand" nature of the Rinnai. We have alredy seen a decrease in the fuel used (when I calculate BTU of oil is higher than propane perunit volume).
The old system used to kick on all the time because the hot water (summer winter hookup) was located in the basement and wasnt insulated very well.
The Rinnai has one more benefit. Im thinking of taking the exhaust and piping it to a proposed temporary greenhouse in the spring. (Just kidding) The exhaust is a rather hot exudate so dont have it hit anyone in a patio space.

We changed over with all high E heating and qualified for the Fed and PA syte tax credits. SO I saved in tax credits alone , about 45%.

The BS from the heating institute has been some of that which is asserting that the fuel savings arent as great as initially claimed. Well, remember that siting as well as length of travel of the hot water is important. (EG is it better to have individual low cap units at each water use centerrather than a "central" heater.

OH another thing that is fantastic is that you can do many heating things at once

I am sure that some of the confusion stems from the wildly fluctuating cost of fuel over the last few years, as the payoff greatly depends upon that and on how we use hot water. But when opinion runs all the way from "it is a no brainer" to "it will never save enough to pay for the up front costs over tank" and they both document their opinion with numbers this begins to sound a lot like partisan politics.

I have a Rinnai R75LSi

Another thing...the one time cost to covert are substantial, as new exhaust, water piping and electric source are needed, but the next time it needs to be replaced a lot less work needs to be done, and it is claimed that the lifespan is about 20 years instead of 13 for tank, and even then we will be able to replace the bad part and not the whole thing (though this is true of furnaces as well but when the heat exchanger goes with them it always is a smarter move to get a whole new furnace). One other thing that I considered is that I have currently a lot of expensive stuff in my garage, and my tank was leaking and could have burst ruining a lot of it. With on demand that potential risk goes away.

Somebody sure saw you coming, Hawk.

When building a new place, I wouldnt give a second thought to anything else. Anytime anything is retrofit, theres a price in the "Undoing" and the refit.
I see that some places have installed heat capture vanes on the exhaust in order to provide heat to crawl spaces or basement areas.

For those who are as useless as tits on a bull, yes, I guess there are, Farmer.

From what I can tell it appears that the on demand manufactures actively discourage going outside of contractors, by being unresponsive if you have a problem and try to get it addressed though warranty work. I would not have tried in any case, as I dont feel qualified to do electrical, plumbing and gas jobs...and putting this in takes all three trades. And I am not up for the risk of burning my house down and then finding out that I invalidated my homeowners insurance by doing illegal work, even if this is unlikely to happen.

Like I said, for those who are as useless as tits on a bull.

Maybe your mileage varies, but I dont know that many guys who would even replace a tank themselves...And we have almost always lived in military housing where all I ever had to do was make a phone call..

JTTs not worth responding to because hes just looking to provoke.

The tax credit assumes "qualified" installation(as does the warranty). So many bubbas try to do it themselves and **** it up so they double their expenses.
Does your base have a central gas service with techs and all? My gas company approved the contractors aand so did Rinnai.

Its a good point about your insurance. Insurance companies are quick to decline coverage when they can prove that you are at fault.
When I bought my old farmhouse it was obvious that the place was originally wored in the 1950's by some dipshit DIYer. We had several close calls in overheating circuits so I hadda have the place reqired and brought up to code and inspected and approved by my insurance carrier. (Farms are under a wider thumb of insurance coverage for several reasons including environmental consequences)

You proved my point, Farmer; lots of "bubbas" useless as tits on a bull.

We own now, as my wife is getting ready to retire and we will stay here. My point was that even though I am nearing 50 YO until these last few years I never did more than make a phone call when my home needed repair work, I have never had the opportunity to even try to do this kind of work for myself.

The warranty problem is what I was getting at, though I do not know for sure that putting it in yourself categorically voids the warranty there are lots of reports of do-it-yourselfers not doing it right and having all kinds of problems in operations and who find that the manufacturer is not even willing to talk to them much less honor a warranty. If either the gas or the water piping is the wrong size these systems have all kinds of trouble running, as the computer is not able to run the system properly. The electric ones often require upgrading the amperage at least to the unit and often into the house so obviously this is something that only a fool would try to do themselves and without proper permitting.

Actually, when I had the gas company install our new hig e gas boiler and the rinnai, the entire cost was almost a throwaway for the material and installation. Rinnai has its tech training requirements that Im sure that JTT has taken. (The computrer chippies and the coding for the gas unit alone required some specific knowledge of coding-Im sure that was not open source).
I am prfectly happy and we love the savings we are experiencing between the on demand gas water heater AND the entire gas heating system, our little farm is toasty warm and weve compared our bills from comparable periods. We are down almost 35%. Also, I had em install one gas fireplace into one of the hearths. (we already had a separate chimney liner for that chimney since we were using a wood stove). Weve burned the gas firplace and we are still down in our heatinmg bills.

They installed the gas tank, heating system, rinnai hot water, and gas fireplace all in 2 days (they did a follow up for several days and then came back and did final grading and seeding over the tank excavation.

I may install another water heater out in my workshop/ studio where I have a small bathroom and I think Ill add a shower . Im going to use the same guys that did my heting system, they were great and we only had one problem. The propane tank gage was not working proprly so they came out, unloaded the tank, popped off the gage and replaced it with another one. That took em all of an entire day (mostly the tank draining and the burning off the pressure took about 3 hours, then the refill took about 20 minutes

What kind of gas, Farmer?

With the cost of energy on the rise, many of us are looking for ways to save on our monthly electric or gas bills. In your search for ways to stretch a dollar, you may want to try a tankless water heater.

If you are an eco-conscious you will choose the tankless system. Not only it cut costs on energy expense there is also less pollution and energy used manufacturing. Yet another water heater at the ten year mark when a traditional system would fail.

After living with this thing for a bit my determination is that I made a bad choice. The three main problems are

1) I need gas to at least double in price before I will be able to save enough in energy costs over 12 years (the expected lifespan of a tank heater) to cover the extra cost of the first time install of the tankless. I hope that this thing lasts longer and that when it goes I can cheaply replace a part rather than the whole heater as is claimed by proponents , because this would save me a great deal of money over 20-30 years, but I am not counting on it.

2) the system is in the garage hanging on the wall backing up to a bedroom. I was never warned that these systems make a fair amount of noise and produce some vibration, which can be heard through the wall by my kid in the bedroom if the house is quiet. In fairness so does the furnace, but that is only on a few months of the year and almost never runs at night because we turn the thermostat down to 62 at night, but this thing making noise all year during early morning showers is not acceptable. The old wter tank was sitting on the floor a few inches from the wall, it made zero noise/vibration.

3) I was warned that hot water would take about 2 seconds longer because the system needs to turn on and get to temp before I have hot water, it reality the extra wait is much longer, like 5 seconds. THis means for the tap farthest away from the heat (kitchen) I am now waiting about 15 seconds for hot water. It seems that hot water tanks have some limited about of ability to keep the water lines warm that I have lost. Before the 140 degree water would go through pipe that had been sitting at maybe 80 degrees, but now it hits pipe that has been sitting at 40-50 degrees. This colder pipe takes the heat out of the water more so than used to be the case. Now I need to wait 2-3 seconds for the hot water to be made and then I need to wait longer for the hot water to warm up the pipes so that I actually get hot water. Also, because the water in the hot line is 125 and not 145 it gets unusably cold after just a minute or two, where as before I could still get hot water for more than 5 minutes instantly , I would just add less cold to it at the tap. What this boils down to is a lot more time waiting for hot water, and wasting water. I live in Washington State so water is not likely to be in short supply here anytime soon, but many areas of the country already are running out of water. A hot water system that causes extra water use is not a good idea long term. Here in Washington the water bill is half standard charges, not charge for actual water use, but in California and Arizona this extra water use waiting for hot water would seriously cut into my already limited monthly savings on gas, making this system even less economical.

Another problem that is less serious is that I no longer have much heat in my garage. In the last year I went to a high efficiency furnace and the tankless water heater, so in the dead of winter I will probably need to put a portable heater in the garage to keep the water lines from freezing a few nights per year. The hot flues on the old systems helped to keep my garage a good 2o degrees above outside, which normally does not get below 20 degrees but we do get a few lows in the low teens or even single digits.

The only noise ours make are at the chimney diwscharge and both of ours discharge up throught the roof. We have NO vibrations at all, In fact its very quiet compared to the old oil burner hot water heater which used to come on with a whump.

It is not huge...the only reason it is an issue is because my house, while impressive to look at, is a year 2000 build in track housing done by a builder who went bankrupt in the process. Structurally it is built to very low standards, I had to put $10K into fixes for problems that I never should have had in the first place. In this case, had the wall between the garage and the bedroom been reasonably well constructed I would not have an issue here.

BTU to BTU basis, Ive been saving fuel . Even though the LPN gas is less btus' /unit, the gas saved by not going into a summer /winter hookup is pretty large. I went from oil heat to gas heat so the constant on/off and the redundant use of fuel for both heat and hot water was costing a lot more. Now Ive been saving about 150 a month (we used to pay 650 a month for oil). Course, we did do some recon and found two unrecognized attic spaces that were not insulated (These were shallow pitched "shed style roofs " that conected several dormers). These areas were like drafty little sitting roomlets that we use for bigass closets. Always cold yet we figured that insulating around them would help (it didnt). We tore out the real plaster ceilings, cleaned the area out and set in a urethane spray foam with silica retardant, then I reframed it and had a guy come in and do the replastering.