I would call Takagi, Rannai & Noritz equal, although each has its +'s and -'s regarding venting, options and capacities. The newest to the game is Navian which is the highest available efficiency and is vented with sch 40 PVC, unlike the others. They are proving themselves to be the future one to beat. Not sure of the others, I know Takagi is capable of doing it too, just haven't introduced a US model.

Units like Rheem, Bradford White and others are just relabeled

A good rule of thumb; if a company has tank heaters, they don't make their own on-demand water heaters.

I think it would be hard to beat the cost of the unit installed by your water company, provided you are OK with the brand. I think the Rheem is a rebadged Bosch. I don't realy care for the Bosch units. Two of my neighbors installed them... one said it wasn't large enough and the other never could get it to work properly... maybe it just wasn't large enough either, but it had trouble running more than one shower and another appliance at the same time. Lowe's took that one back.

I'm partial to Noritz since they have been around the longest and they have the widest array of choices with the most up to date burner systems. Check them out on the web. There are a few sellers of Noritz units on eBay. I didn't buy mine there but have purchased some accessories. Whatever you do, do NOT pay retail. Big discounts are available.

I recently finished the DIY installation of my Noritz N-084M unit. This unit is a couple of years old, but it has a lot of capacity (more than you need at 236K Btu/hr) and works really well.

The latest Noritz has two heat exchangers so it can recover waste exhaust heat. The efficiency is 92% and they can run PVC exhaust piping. Had I not already purchased my unit a couple of years ago I would have probably gone with this unit today.

There can be a lot of hidden costs regarding tankless units. Since ours was so large, and our meter was so small, we needed a meter upgrade as well as a new line to the main because we were also adding a rangetop, fireplace insert and BBQ grill takeoff. That was $2700 extra cost.

Virtually ANY tankless WH will require a gas piping size upgrade as none of them will run on a 1/2" line. Make sure that is included in the quote.

You see a lot of Rinnai units on the home remodeling shows, but I suspect the main reason you see them is Rinnai provides the units at no, or low cost. That said, they seem to be a decent unit.

With a tankless I think you need to get the largest unit you can afford and reasonbly install. The biggest complaint seems to be undersized units. Our Noritz has plenty of capacity to run at least two showers at once, which is pretty much the maximum load it will see. I'm sure you could get by with a smaller unit since you only have 1-1/2 baths.

Don't expect a tankless unit to provide "instant hot water." It won't. In fact, it will most likely take a little longer to get hot since it has to turn on and heat the water on the fly. So far this has not been a problem.

There are other minor annoyances reported by some people, namely the "cold water sandwich." This occurs when you use the unit... say you take a shower. Then you wait 15 minutes or so and someone else takes a shower. If you have insulated piping the water in the pipes is still reasonbly hot but the water in the tankless has cooled down. This cool water gets sandwiched in between the hot water in the piping and the newly generated hot water. It can be an unexpected surprise in the shower.

With a little rethinking on how you use hot water the cold water sandwich can be avoided. In fact, with a tankless it's good to do more than one thing at once because the unit is already turned on and making hot water.

It will be a couple of months before we'll know if we are saving gas... but that's not why I installed the unit. I wanted the endless hot water. With all the extra costs we incurred the payback will probably be 50 years!

Good luck.

Per the Rheem tankless thread.

My gas meter was upgraded 3 years ago. I wanted to run a natural gas BBQ and a line had to be run over 50ft form the meter to the back patio. The original meter wouldn't cut it. Gas company here (TECO) does free meter upgrades when you are going into a situation where you will add to your use. I think I heard them say it was upgraded to a 2 1/2 lb (or ton?) unit. Don't quote me, I could be TOTATLLY wrong.

My current hot water heater is a basic 40 gallon tank inside my garage. It's no more then 10 ft laterally from the meter outside. It looks like the current line to the heater is 1/2 flex, but it would be pretty darn easy to upgrade given how close it is.

The current heater is vented directly out the room, a straight shot in fact. Looks like 5-6" ducting. Looks like thin galvenized metal to me.

Been browsing the noritz site. I see something like the N-0931-NG available on eBay for $1600 ($2100 MSRP). Do I have to worry about warranty if I buy on eBay? Do Noritz/Rianni/etc. require you to buy from licensed distributors to get warranty, or is that not the case?

Also, I see there is indoor/outdoor and indoor direct vent. As I mentioned previously, I have a direct vent on top of my current gas hot water heater which goes straight up into the attic and out the roof. The unit is in my oversized 2 car garage. Would I be after the indoor/outdoor model or a direct vent model given this environment?

Noritz is descent I always recommend the Rianni. Thats the going product around here. Not sure if they would warrenty the heater if bought off of E-Bay. Thats something you will have to find out form the supplier. If I had to guess I would say no. As said before 3/4 gas is the smallest size that will feed any tankless. If you are going to install it in your garage you need the indoor unit. The only difference of the indoor/outdoor is that the outdoor is vented within the box no need for running a vent because its outside. Ususally we intstall them on new houses inside the brick.

The eBay seller I have used in the past for Noritz was something like "Advanced Energy Systems." Not sure if they are an authorized dealer but they said they can get anything Noritz makes, so my guess is yes, but you'd better check.

Before making any decision you need to research the venting options more fully. Rinnai uses a concentric vent/intake system and I believe they have restrictions on how far away from an outside wall you can be.

Also, Noritz does not like to vent straight up and through the roof. If you want to go through the roof you need to vent up a few feet, add some length of horizontal run and then go up and out the roof. Check out the various owner's manuals.

The N-0931 sounds like overkill for your situation with only one full bath. That unit is over 250K Btu/hr so it will require a large line. Sounds like you have a "pound meter" with extra regulator. That's what I have. You should have plenty of gas, you just need to get it to the unit.

Local contractors may not want to install a unit purchased on the Internet. That's what I ran into. Consequently, one quote was for $4000... so, aside from the gas piping, I did it myself.

It would be good to step back a bit.

Other than the Bosch unit that had so much trouble (AquaStar?), I don't think that the brand of the unit is the most important issue. You first need to be clear on what your needs are and what venting and other issues you may have.

To determine what your needs are, you need to approximate the temp of the inlet water in the winter--In very cold climates that can be around 33 degrees. Then you need to determine what you want to raise that temp to. In most cases the design temp is 105 degrees because that's the temp of a shower (even though the heater will likely be set at 120). The difference is the temperature rise.

Then you determine what faucets you are likely to use at the same time and you add the gpm rating of those together.

Once you know the temp rise and the flow in gpm, you can find a heater that will do that. They publish charts that show how many gpm they will heat at a given temp rise.

What you will find is that the most of the heaters have a similar energy factor and so a 200,000 btu input heater, for example, will heat about 4.5 gal a minute at a 72 degree rise.

Once you go over the 200k btu input, there are fewer brands available, but still several.

Be aware that the condensing units (that take the flue temps below condensing point) get very expensive and have the issue of the condensate being corrosive. At this time, I wouldn't use one unless there was a compelling reason to do so. (The little additional energy savings isn't a compelling reason, Solving a venting problem because you can use PVC pipe might be)

All of that said, I thing the Rheeem/Rudd/Paloma units are a quality unit at a reasonable price. The cost of 200k btu Rheem is ~$1100 with the basic vent kit. If your gas company will install it for $1500, I would do it. That includes the cost of capital, by the way.

Most of the units are available as an indoor unit or a outdoor unit. The outdoor units are suitable for warm climates and don't need a vent. Most of the indoor units also offer an outdoor air intake.

I am thinking about a tankless water heater but talked to a neighbor who told me he has a problem with his.
He says with his that if he try's to take a cool shower the unit will stop heating water and turn cold right away.
Is this an adjustment problem or do they all work like that?

All tankless heaters have a minimum flow rate that must be maintained or they shut off. It is a specification to check when you are looking at a heater. Lower is better.

Most of the time, that is between .3 and .5 gallons per minute and it's not a problem.

There was one heater, the Bosch Aquastar, that required one gpm as a minimum flow because it used that for power the igniter.

This was a bad design, for several reasons, but one of the problems is that it can be difficult to keep a gallon a minute flowing through if you don't need that much hot water.

I would guess that your neighbor has one of these Bosch units.

I can't speak for other manufacturer's units but the spec on my Noritz N-084M is 0.75 gpm to TURN ON. I think once it's up and running you can drop that down because I have been able to lower the water flow rate at the kitchen sink to what seems like a much lower value and it still makes hot water. The newer Noritz units have lowered the turn-on value to 0.5 gpm.

Are the electric tankless, ok also? And do they corrode up bad in hard water and need a lot of service to keep clean in hard water?

You would require almost a 120 amp breaker to equal the max output of a gas tankless. They are ok for point of use applications but less so for whole house.

Rinnai is the market leader and has been for the past 15 years. Rinnai has a 45% market share in the US. That is why Tom sees them in all the home shows.

Minimum flow rates to initiate operation are very very important. My new Rinnai RL75 has a .4gpm requirement to initiate ignition. It will hold operation down to .25 gpm.

Whipsnade, your neighbors problem may be that the shower valve is leaking by, or he is running the water heater at to high a temperature. I run mine at 120 in the winter and 115 in the summer. You typically shower at 105-110. At 120 I have no problems with my system. Your neighbor should be able to read the actual flow within .1gpm thru the unit to determine actual hot water flow to that shower. That is done on the touch pad supplied wight he unit. For instance in my home with a 2.5 gpm flow rate to the shower head I use 2.1 gal of hot mixing with .4 gal of cold to arrive at my shower temp.

For a two bath house I would suggest the RL75 size unit. Mine fires from 10,000-180,000 btu. At a 70 deg temp rise it will make 4.3 gpm all day long.

"Don't expect a tankless unit to provide "instant hot water." It won't. In fact, it will most likely take a little longer to get hot since it has to turn on and heat the water on the fly. So far this has not been a problem. "

I can't go into explaining the physics...but...by definition, a tankless heats as fast as taking water off of a tank. When you open the HW tap in my bathroom, the Rennai about 10 ft. away fires up instantly. I mean, instant...by the time you've moved the tap the full 2 inches, it is running. It often surprises me that there's no delay but there isn't. I guess the speed of a pressure drop through a pipe is close to instant.

What is problematic is people don't install them correctly. Rather than put them near the POU they put them down in the cellar like a typical tanked water heater. Does the utility install them correctly or just put them where the tanked water heater was? Probably the latter.
Mine is in a closet/utility/laundry room connected to my bathroom, and it was a great choice to put it there. My old water heater was at least 60 pipe feet away, and because I have lowish pressure, it took 2 or so minutes to water for hot water when showering. Now it takes 10-15 seconds. Of course, when I got the utility to temporary boost the pressure and flow, it was only a couple seconds. For some idiotic reason they say that's not possible to fix in the long term. BTW even w/only 30 or so psi, even a 1/2 open tap will trigger the Rennai to start.

Actually...I will slightly alter that.
The reason a tanked heater might appear slightly faster is that, in fact, the tank is heating some water in the pipe all the time. But the whole point is the tankless is it can _instantly_ heat the water to as high a temp as the water sitting in the tank. The poster above implies a little water has to flow through to warm up or something. No. If I open the overpressure valve on my Rinnai the water is scotching hot after 1 second at most. Probably less.

But the difference is trivial and under no normal circumstance could be noticeable. Because of the low water pressure and long pipe lengths in my house, I have a small tanked heater in my kitchen, under the sink. IF you compare the laundry sink tap that is 2 ft. from the Rinnai and the kitchen tap with a tank 2 ft. away, the response time is if anything slower from the tank.

This post was edited by davidrt28 on Fri, Jun 6, 14 at 12:00

David is correct on the placement issue with tankless. Essentially what I told my customers is you do not want to perpetuate the mistakes of the original low cost bidder. Making the investment in a new tankless water heater in place of an old tank is the time to analyze the whole system. What I always have said in my training programs is to go ahead and bid the job with the tankless in the same location. That is position A. Then, go for a walk around the house and see if there is a position that is better for the long term. Meaning less water waste, less energy waste and less homeowner comfort (delay in hot water). That is position B.I then tell them to explain why position B is really the best for comfort efficiency and long term satisfaction. That is good customer service, good business and good sense.

I just re-modeled our home. New baths, kitchen and Laundry. I was able to position my tankless so that the longest hot water run is 16' from the water heater. That has substantially reduced my delay in hot water delivery as well as reducing water waste, and here in CA with our drought I am all about saving energy, but I am more about saving water. Sadly, our neighbors across the street had their well go belly up this past week.

For gas, Takagi and Rinnai are the safe choices. I am a bit fascinated by Navien NR-240A because it has an internal recirculation pump that is said to help with the hot water delay and in theory it should. But checking the product on Amazon, I was surprised to see lowly it is rated by customers.
I think electric tankless water heaters are also fine as long as you have a 120 amp breaker. What I like about them is they are just too easy to install. A DIY person could get one of them working without an electrician. Needless to say that you need no venting with electric. Best electric tankless water heater is probably Steibel Eltron but people also like Rheem because of the better pricing.