That article is bogus. In doing the cost comparison, the author
assumes that the tankless gas water heater always uses gas at its peak
rate, which is false. A tankless gas water heater has a modulating
gas valve, and it will only use enough gas to provide the required
temperature rise. It is incontrovertible that all other things being
the same, a tankless heater without any standby losses will use less
energy than a tank heater with standby losses.
The author also complains that tankless water heaters provide a
constant temperature rise, so that the hot water is hotter in the
summer when the incoming cold water is hotter. While I believe some
older models do this, most current models will modulate the gas usage
to provide a constant output temperature as the input temperature
In other words, the article's two chief complaints are invalid.
Right Wayne, The modulating burners go from something like
18,000-190,000 Btu for the Takagi, My little Bosch does something like
The Energy Factor is a True rating nobody making a tank wants to
discuss, and few consumers are smart enough to ever check, that is your
true rating. Plus rated unit Efficiency. The true tank standby loss is
excessive and pipe heat loss im sure not included as very few people are
smart enough to install thermal couplings on there water heaters.
Now consider tankless 30 year life, no tank to rust out, its all copper
Now consider tanks scale. Rated efficiency is downhill from year one, I
just removed a 20 yr old tank with 12" of hard scale, now that lowers
efficiency alot, tankless do not build heavy scale, but should be
delimed every few years.
The article does note that tankless water heaters don't run full blast
whenever they're used. I guess you missed that part.
The author does his calculations based on peak use, which is valid as
long as he compares the cost of the conventional water heater on the
The author's addendum to the original article notes this, but he
doesn't redo his calculations.
The author compares the measured monthly usage on a tank water heater
with an estimate of the tankless usage. The tankless usage estimate
is incorrectly computed assuming the peak firing rate whenever any hot
water tap is open.
In summer with 70f incomming I an turn my bosch at its lowest setting
apx 30000 btu and the water is still to warm for me to take a hot water
only shower. Now the Rinnai - Takagi have lower Btu modulating valves,
so Btu to operate can be very low, that is why I have a total 6 dollar
Ng bill in summer.
I have the Bosch 125 natural gas water heater and I am happy with it.
I have had it for 4-5 years and have had no problems.
The Bosch 250 might be the one for people who want to run 2 things at the
A 125 at each end of a large house would probably be better.
Ours has a regular 5" flue but you can get the one with the power vent that
uses 3"-4" pipe and doesn't have to be pitched toward a chimney.
"Scott Townsend" <scott-i@.-N0-SPAMplease.enm.com> wrote in message
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