The good news is that you aren't an early adapter... Tankless have been out for a while. Mine is three years old already, and I wasn't that early out the gate. The other thing is that they have been using tankless in other parts of the world for a long time.

You need to do a little math (actually, your plumber needs to do it). The tankless needs to be sized so that it can produce enough hot water to supply all of the anticipated simultaneous hot water needs at the coldest time of the year. This isn't all of your hot water outlets, just the ones that would happen at the same time. Typically this is the number of showers that would run at the same time.

I too have a 2 br, 1 bath house. So, for example, my water heater will heat enough water for 1 shower (2.5 gpm) and the bathroom or kitchen sink (2 gpm) to 105 degrees with the water inlet temperature at 34 degrees (Jan, Feb... -15 degrees in Indiana)

In what part of the country do you live?

You will have a better idea about gas supply once you have properly sized the unit.

Something else to think about is where the heater is located. I was able to move my heater 20' closer to the bathroom and kitchen when I went tankless. You want to keep the vent short - because the vent materials are expensive.

As for brands of units - I have a Rheem and I'm happy with it. Rinnai and Takagi are other popular choices. For your application, I'd stay with a non-condensing unit. I would probably avoid Bosch units - they had some real problems.

I wanted to get a tankless water heater, but there are a few things you should know before getting one.

1: They are expensive. Note the cost of getting one is not just the heater, but you may also have to re-plumb the water lines. This can get expensive.

2: Maintenance is expensive. Due to the way they super heat water, you need to make sure you have soft water in your area or treat your water. If not, scale will quickly build up in the water heater and require expensive repairs.

Here is some info. to review:

http://www.plbg.com/education-tankless-water-heaters.html

Due to cost, I'm not sure a tankless system is "economical" in the long run. It's nice if you want to free up some space, but beyond that, I'm not sold.

Mike

gas size has to be looked at by a plumber who sizes gas.
you would want to get a th2 because of your venting and then you will need servicing valves, de-scaling filter, and and a condensation pump.
th2 like 1,800
serv valves 125
descaling 125
also a bi- yearly servicing plan.
you get 30% tax credit
300 from local goverment.
cost of instal 1,500 - 2,000 depending on gas.

I'm sorry, I disagree with wisehvac.

You don't need a condensing unit. From what I gather from your post, you can mount this on an outside wall and vent through the sidewall.

My unit cost me about $1,100 for materials including the vent kit, service valves, gas and water lines. I did the work myself, but that's significantly less than what wisehvac is talking about.

There is a 30% tax credit, and you will need your plumber to size the unit and then calculate the gas line size.

In my case, I was fine and didn't need any changes.

I did run vinegar through my unit for the first time after 3 years to remove any lime buildup. If you have hard water, you will need it done more often. If you have soft water,you won't need it cleaned every year.

wisehvac. How much would it be for a full install including the serv valves/descale without tax credit? Just want to make sure I have a good idea on price...

Mike

I got a quote between $2700 - $3900 for a full install + tankless.

I suspect that the lower end of the price range is more realistic/ reasonable. No surprises as to which quote was more agreeable to me.

Re-plumbing the water lines is not a big issue imo.

realy depends on how hard it is to install and vent run itself
there are a few different styles oe condenses which uses pvc and other uses category III S.S.

tk3 would be about 2,700
th-2 I just priced out at 3,400.
sometimes the smaller quote from a different plumber does not include sizing out gas line or de-scaling filter or servicing valves or correct venting.
jake your right you don't need the condensing type but where your doing long runs you might want to consider.

1: How effective are the descaling filters?
2: What's the maintenance like on the unit with a filter?

I don't have the link now, but I remember reading that there a part in the water heater that can fail due to scale that are expensive to replace.

Mike

Wisehvac,

I do suggest that people consider a condensing unit if the flue run is going to be long. SS flue is expensive and can quickly make a tankless install unreasonable in price.

The OP suggested that it could be placed on an outside wall and vented through the wall - a great feature for tankless which results in a very small flue run. (mine vents out the rim joist area).

"1: How effective are the descaling filters?
2: What's the maintenance like on the unit with a filter?"

Although its classified as a filter, it filters nothing and acts as a Scale Inhibition System. Its a cartridge with an inhibitor material that is absorbed into the water to assist in keeping the dissolved solids of mainly calcium and lime from sticking to the hot superheated surfaces of the tankless heat exchanger. These are just a smaller version of the "Everpure" units you will see in restaurants servicing ice machines, soda/coffee and so on.

There are "rust, scale, dirt" filters on the market, not to be confused with the item above. These "scale" filters may be capable of filtering out hard particles but do nothing for hardness in the water that gets flashed out from the water in the heat exchanger and stick to surfaces.

Maintenance, depends on hot water usage, they typically last between 6-12 months and a replacement cartridge can cost about $25-$30, DIY.

Here is a link that might be useful: Heres one Inhibitor system

update from original poster: here is more info and quote for your review from plumber #1:

i have original galvanized plumbing. eventually i will upgrade but not planning to right now (tapped out from the kitchen remodel). i live in northern CA (SF Bay Area), it rarely freezes here, winter is mid 30's, usually warmer than that. the unit will be mounted in my sub-basement under my house, it will not be outside. it is about 10' to the side wall of the house where it will need to be vented. to clarify for the poster who suggested i stick with a tank, i can't due to the need to remove the flue in kitchen and headroom in sub-basement will not accommodate the power vent tanked kind (wish it did as i would buy one and case closed..)

it is just me in the house so max usage at one time is one shower and the washing machine. one quote so far:

he recommended the TK-3, quoted $3800 ($2660 after tax credit) which included unit, materials and labor: install unit, run a 1" gas line from meter to unit, install earthquake auto shutoff valve at meter, provide and install new 3/4" copper water supply lines from existing lines in sub-basement, insulate hot water lines from unit to tie point, install SS flue pipe to sidewall of house, patch exterior, provide and install T&P discharge line, provide electrical to unit (not sure what that means, have question in to him), permit included in bid. does this sound about right and are there any questions i should be asking? what kind of maintenance is required for this device? frankly i like my existing tank that works just fine and i can ignore it. don;t have a choice so want to understand what i am signing up for with this new model.

the other model he quoted was the eternal on demand hybrid which is more expensive and unproved track record since it is so new on the market. for my needs he suggested i stick with the TK-3. the quote for the eternal was $4700, same install details as above plus the condensing line.

should be maintained onces a year,
should have descaling filter installed
they don't recomend having galvinized pipe
these water heaters are sensative
tk jr might be more resonable .....
your only going to run one shower at a time, also do uyou use hot or warm water. or mostly cold? Id go with the jr.

Did you try http://betterwaterheaters.reachlocal.net/?

They service the bay area CA.

I'd recommend getting multiple bids (3)

The main things to ask about are
1. Length of gas line to be installed. Typically, installers in the SF bay area will use CSST (stainless steel flex pipe).
2. Electrical - plug in socket or hard wiring?
3. Is the flue line long enough that a condensate drain is required.