Wow. I get away from the computer for a weekend and all kinds of info/comments get posted. I'll apologize in advance for the wordiness.
Re: prices that are quoted. Most installers are not happy having to charge what they do charge, because they don't sell as many of them. Its an expensive product with little markup. The units are not "cheap" at the prices that the installers pay to purchase the equipment, then they have to install it. Place some of the blame for the excessive costs on the manufacturers, too.
The costs involved to install the units properly is not cheap. The cost of gas piping continues to go up substantially and the amount of time that is involved to do the gas piping can be considerable - particularly if you are running a gas line across the entire length of a house. Then there are issues of a finished basement vs an unfinished basement. Then you have to wait for the inspector.
And I won't even begin to address the liability involved.
Anybody want their house to go "Boom!" ???
Another item: one of the things that makes the Rinnai so much better than most of the rest is their gas control valve. This valve is good enough that it controls the amount of gas that is used by the unit in ONE btu increments. These units will go up to 180,000 btu's and more. This is more than some gas furnaces! Most of the other tankless waterheaters that I have seen only have a high/low fire. Maybe someone else knows something about the Bosch or Noritz (or other gas tankless WH) and how good the gas control valve is?
Something else to remember is that the gas tankless waterheater produces enough hot water at a certain efficiency over a certain temperature rise. So, the incoming water temperature plays a BIG part on how efficient (and effective) the units are. That is why the Rinnai tankless units start out at 180,000 btu's. They HAVE to have that kind of power to produce the temperature rise needed and still generate a decent flow rate to the rest of the house. If your water source is ground water (well water), then that temperature rise is fairly constant year 'round. If your water source is surface water (municipal water that comes from a lake / river / etc), then that temperature rise will change seasonally and gas usage will increase/decrease seasonally. Our municipal water will change as much as 15 degs F seasonally. So, the water may not get as hot as you think it should in the winter - and/or the flow rate is reduced because the unit is unable to generate that kind of temperature rise that you are requesting.
If you are interested in purchasing a gas tankless waterheater, one of the best ways to limit the installation costs involved is to get an exterior unit and to place it as close to the gas meter (natural gas) or propane tank as possible (running gas piping is more expensive than running water piping). If you've got to have an interior unit, then the additional expense is going to be the vent piping - which is specially made to handle the exhaust gases.
Someone mentioned the condensing tankless waterheater. There are gas condensing tanked & tankless waterheaters and electric tanked condensing waterheaters. Yes, they are even more efficient than the regular tankless waterheaters - but they are another step more expensive for the units themselves. Some of that cost is offset because for a gas unit, you don't have to have special vent pipes, either, for the interior tankless Rinnai units. I don't know how popular they are (over the regular tankless units) because we haven't had to service any yet.
In houses / small businesses where you don't use a lot of hot water, tankless may be the way to go - so that you are not heating water the same way that Cleopatra did - by lighting a fire underneath a container of water. But if you have a large family, several teenagers in the house, or simply like to fill up that whirlpool in the evening when you get home, you may be running out of hot water in your tanked waterheater that may take several hours to regenerate. However, if the payback is not within your timeframe that you are willing to deal with, don't do it. Its an expensive choice to install one and then find out that you really don't like it. Some people just don't.
Oh, someone mentioned natural gas and the expense of bringing a gas line across the street. If that is the case, go with a propane fired one. You have to have a certain sized tank (maybe 100 gal propane tank???) to provide enough gas pressure, but it is workable. We have a 300 gallon propane tank buried in our front yard. There is just no natural gas on our street and we weren't going to pay to bring it up the hill at least 2.5 blocks.
Sorry for the wordy input.
The thing to remember is that there is nothing wrong with the tankless waterheaters - as long as the homeowners / property owners understand EXACTLY what they are getting in to. Many plumbers simply don't WANT to understand what makes these units tick and therefore become poor spokespeople for selling/installing these units.
AJ
