Just curious, will be looking to replace my unit and was wondering what the
consensus was here. We have two showers, not used at the same time, washer,
one outdoor hot water spigot, and a dishwasher. Both the shower units and
laundry are on the second floor. Any input is greatly appreciated.
I have researched this and the one to go with seems like the Bosch (or
Tagaki sp? made by bosch). But make sure to get the bigger unit. It seems
that people are very happy with that one, but most research I have says they
are unhappy with the smaller unit. BTW you can vent those out the side of a
Ihave a Bosch 117000btu gas it is great for one shower. for 2 you will
need the larger 180000 Btu units . Bosch, Talagi and Rinnai. Rinnai is
the highest efficency made. You will need a larger gas line for all that
BTU. My payback is 4 yrs from switching from electric tank, but my
electric costs are 3x that of gas. You dont say if you are Ng or
electric or propane. Costs vary over the US. so run your numbers on Btu
costs. Im very happy with the Bosch Ng unit
I have two homes - one in PA and one in FL.
The PA home has an oil furnace that is tankless for hot water. When you
turn on a faucet - the furnace goes on and makes hot water for you on
demand. It is a bullet proof system and very efficient. It also makes
hot water on demand when the baseboard radiators call or heat. the unit
is about 2 x 2 x 3 feet.
The FL home has a heat pump and two electric water heaters. The pipe
runs are long and you wait forever for the hot water to get to the
What is your KWH cost and gas per them. Most of the US has much cheaper
Ng. My electric costs are 3x that of gas in the midwest.
If you will run 2 showers at any time or have a family the smaller
117000 btu Bosch will not be enough, the 180000 btu Takagi or Rinnai
will handle it. Takagi heats to water temp rise so as your water temps
get colder in the winter so will output. Rinnai heats to water temp and
is 88% efficient vs 83% for Takagi [Takagi makes Bosches large unit]
Both have remote thermotats which are a good option, you can put the
thermostat in the bathroom. Rinnai I believe has the best warranty. You
will need to upsize your gas supply big time , so figure that in first.
With electric tankless for a small one shower unit Bosch you need a
dedicated 120A circuit-alot of power, Not many have that extra capacity
for even a one shower unit.
I have the small Bosch 117000 BTU unit and am completely satisfied. My
payback switching from electric is 4 yrs. In summer with gas dryer and
cooking all food-Ng my gas bill is 6-7$ a month , Electric was reduced
25-30 a month. Yes the initial cost is high but tanks get reduced
efficency every year from Scale-sediment where Tankless remain the same.
Also Tanlkess coils should last 3x as long as tanks. It is a worthwhile
The Extra 5% efficency of Rinnai vs Takagi and the way it heats to
temp, not temp rise as others would make it my choise.
On Wed, 2 Mar 2005 06:54:35 -0600, email@example.com (m Ransley)
The Rinnai 2532FFU is the one I am leaning towards, but if you
really want to pump out the hot water I noticed yesterday that
Noritz is now offering their Model N-132M, which they say puts out a
maximum 380,000 BTU for 13.2 gal a minute at a 45-degree rise in
Of course at a $4,000 US sticker price it's a little steep for my
Also, the following was passed along to me by a sales person and you
might want to consider it when you look at brands:
Paloma is manufacturer for Rheem and Ruud.
Rinnai is manufacturer for Bradford White.
Noritz is manufacturer for A.O. Smith/State.
Well, if your service can handle it (the tankless units require as much gas when
operating as a furnace), I'd go with a tankless gas. Takagi, Bosch, and Rinnai
are all good units. If you live up north, be sure to check the flow curves to
make sure the unit will put out enough hot water for your worst-case cold water
temperature -- most won't put out full flow when input water temperature is
below 50F or so.
Personally, I have a Takagi TK-2. It's been a nice unit, and I've never had to
worry about "too many loads" -- I've had the washer, dishwasher, and 3-head
shower (each head 2.5 gal/min) all going at the same time, and didn't lose any
noticeable pressure. Only real downside is that it takes a number of seconds
longer to get hot water for a small load (say, a faucet) compared the old tank.
Upside, of course, is I can fill the whirlpool tub (or take a l-o-o-o-o-n-g
shower), and never run out of hot water.
Tankless heaters are the least efficient of all water heating option
and the most costly to operate.
They are inefficient because when heated by combustion, far more energ
is required to heat the same amount of water as a conventional heate
and much of that energy is wasted as excess heat sent up the chimney.
Tankless heaters must always cold water to hot water quickly and canno
do it uniformly or cheaply. Tankless heaters, because they do not stor
water, must always take cold water and raise it it use poin
temperature quickly. This takes a LOT of energy and a lot more energ
than maintaining 40-50 gallons at point of use. Since you can in winte
need to chrionically heat 32 degrees or colder water that enters you
home from outside, because they cannot store water that has alread
been warmed, require far more energy than conventional tanks.
Even though electric tankless heaters would be most efficient becaus
they do not waste any energy up a chimney, you are still forced to hea
extremely cold water and have no way to store water already warmed.
Finally, tankless heaters have a difficult time provide water at
constant temperature and one of their greatest drawbacks is not bein
able to provide a good steady stream of even temperatured water.
Bottom line is, unless the tankless heater will be for point of use fo
a single appliance or used to pre-warm conventional heated water after
long distance, they will not help with the bills if you wish to use the
for a whole house and with a large family.
Coventional electric water heaters remain the cheapest and mos
efficient form of water heating.
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manhatten42 what you wrote is the biggest bunch of bullshit ive seen
here in awhile, Yes I own a tankless gas Bosch , that has reduced my
bills so much I have a 4 yr payback from switching. Your standard water
heater is no more efficient than a tankless. Rinnai tankless are more
efficient than most tanks.......
2 other things you forgot, gas tanks do not maintain rated efficiency
as tankless do and tankless coils last 3 times longer. Learn about what
you write before posting more bad advise
Your analysis is wrong. Tankless is the most efficient way to heat
water for domestic use and saves money.
The tankless have very efficient heat transfer units which imparts the
kiinetic energy from the ignition source (Ng, propane or electric) to
the water. It takes less energy to raise the temperature of a small
quantity of water (heat exchanger) than a larger quantity (storage
tank) because of the prinicple of specific latent heat of
vaporization. The wasted heat (energy not directly imparted to the
water) is minimized and efficiencies of 80-92% are achieved with the
Oulet water temperature is monitored and regulated. If the output
temperature falls below a preset or the temperature differential
between the inlet water and output water temperatures exceed the
design limits of the unit, the water flow is restricted. This allows
more time for the kinetic energy from the ignition source to be
imparted to the water, maintaining the water temperature.
Storage tank systems heat the water continuously 24x7. Energy is
wasted as heat loss to the surrounding atmosphere because the
insulation on the storage tank is not 100% efficient. When the demand
on the water is great enough to depleat the hot water in the tank, the
water temperature drops. It takes an enormous amount of energy to
reheat the water after the demand is removed. The large mass of water
has a constant heat absorbtion rate and a temperature differential.
mass of water x specific heat capacity x temperature change
is the formula to calculate how much energy must be imparted to the
water to raise it temperature from start to boiling. A large quantity
and large differential will require a large input of energy. Very
expensive in term of Ng or electricity prices.
Other things to think about. If you are the type not to repair leaky
valves, then you waste water AND energy if you have a storage tank
system because you discard hot water. If you have a tankless system,
you only waste water because the flow rate of a leak is not enough to
trigger the heating process.
On Tue, 1 Mar 2005 11:40:58 -0600, manhattan42
I recently switched my 28 year old storage tank water heater for a
tankless Rinnai unit. A replacement tank would have cost $1500; the
Rinnai cost twice that. Installation costs would have been the same.
The savings I can't say exactly but I suspect that they will be
significant. I estimate that I will pay back my costs within three
years through Ng savings.
What I looked for was efficiency (energy in to energy out ratio) of
around 90% or better. The Rinnai gives me 92% I believe. I also
looked for reliability of mechanics. Rinnai is tops here as well. The
third factor I looked at was the installer. I regarded three
installers and picked one that had a history of good customer
relationships and dependable service history.
I evaluated one other feature that swayed my choice to a Rinnai. The
Rinnai I bought is a combo unit which means I can use it to heat the
house as well as serving my domestic hot water needs. The installer
will replace the Ng burner in my furnace with a heat exchanger unit
attached to the Rinnai, leaving the air filter and blower unit intact.
The Rinnai will heat the water to 180 degrees F and circulate that
through the heat exchanger in a closed loop. My furnace is 78%
efficient, the Rinnai 92%. I will save additional money through
reduced Ng consumption. I'm not sure the efficiencies of the heat
exchanger in the furnace core but I suspect it is very high.
When I researched I found a few articles helpful on the web:
Incorrect. It takes 1 BTU to raise 1 pound of water by 1 degree F
regardless of what heater is doing it. Simple physics. But tank heaters
send more heat up the chimney.
That guy used bad math. He assumed that the tankless heater would use
168,000 BTU/hr regardless of how much water was being drawn through it.
He has no basis for that assumption and he certainly did not measure
it. His bad calculations are outof line with others' direct experience.
One caution here, it is important to distinguish between a tankless
water heater which is specialized for domestic hot water vs. a tankless
water heating coil which is an add-on for the home heating system
boiler. The latter is cheap but not particularly efficient.
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