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recent boiler replacement

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Joined: Mar 24 2003

Just saw my heating bill last month and OUCH! I am once again looking at a replacement for my 1971 AO Smith which according to 2 experts is in good shape and could easily see its 40th if not 50th birthday.

Has anyone recently replaced their boiler? I am on the fence regarding tankless water heaters versus boilers although I admit to be more inclined to replace like for like (this isnt meant to solicit pro/con of each so please let us not!). I do not see much value in a tankless system (some claim that they get "free" hot water) for myself since I have domestic water recirc loop (mainly to keep pipes warm in the winter).

Basic research seems to indicate the boilers are around 2200-3500 or so for around 120,000-140,000 btus (various efficiency ratings are 85-93). Can people that have replaced theirs in the past few years comment on total price and brand chosen? Also, do the energy efficiency claims live up? If I could save 200/month, it would probably be worth it...but not if I gotta spend 10k to do it! We have relatively short heating requirements in Walnut Creek so major usage is only 2-3 months per year. A 4 year payback is the longest I'd like to go but I admit to be driven by doing the right thing...I am also considering PV but thats a longer thread!

Lastly, I would not mind compiling heating much do people spend on natural gas per month (better yet, what quantity of gas), location, heated area, year built, insulation improvements, other heating sources, and what is their temp setting? If people wanna keep things private, I will mask the information so just send directly to me.



Joined: Mar 24 2003

Anyone? :)


Joined: Mar 21 2003

We replaced our original 1958 AO Smith boiler with a Munchkin Contender last fall. And the water heater we replaced with a "indirect" unit that is heated off of a loop on the Munchkin.

We don't have a full season to compare yet but the observations so far:

1) The indirect domestic hot water may be costing us a little more than the old conventional gas water heater. On the other hand it is setup so that we can easily add a solar heating loop to it and that should cut gas costs.

2) If I read the climatological data correctly, December 2007 was colder than December 2006 or 2005. Despite that our gas usage as measured in therms was down about 20% from the average of the previous two years. So it appears that the high efficiency boiler does help there.

However the savings cannot be paid by in anything close to four years. Maybe 10 or 15 years. Our goal is/was to reduce our carbon footprint and it turns out that domestic natural gas use is, for us, the single biggest contributor to that.

Joined: Nov 26 2004

you can find reliable guidance on price range for replacement here:

we ended up paying around the mid-point to have our original boiler replaced with an Alliance Super Hot. It works well however the cost to run it seems to be about the same as our "original" boiler.

That being said, my personal observation would be that replacing an operational boiler with a newer boiler (that is supposed to be more energy efficient) in the hopes of lowering your monthly bills isn't all its cracked up to be.

Joined: May 28 2005

Tod wrote:
We replaced our original 1958 AO Smith boiler with a Munchkin Contender last fall. And the water heater we replaced with a "indirect" unit that is heated off of a loop on the Munchkin.

I am in the same neighborhood, with a 1959 AO Smith boiler. My hot water heater just broke, so I am interested in exploring this all-in-one solution. Would you mind sending me a message telling who installed your system? Thanks!

Joined: Jul 6 2003

We replaced our boiler about 5 years ago, the original was from 1960. The old one never kept the house warm, no problem now. Our new one is an instant heater, I think it's a Takagi. I don't think the monthly bills are any smaller but the house is much more comfortable.


Mark Hoy Sunnyvale Eichler Owner

Joined: Jul 20 2008

My architect has something called a Munchkin that serves as his boiler for radiant heat and as his tankless water heater. It is about 95% efficient. He says it is not cheap, but has not had so much as a hiccup in 6+years. I am looking into it.


Joined: Aug 30 2005

We live in San Rafael and need to replace our original boiler ASAP. Can folks in the area who have replaced theirs recently please email me directly with info on what they installed, who installed it, cost and level of satisfaction? THANK YOU! email:

Joined: Mar 16 2005

You seem to be asking several questions.
(1) We are in Sunnyvale so we get more Winter than the East Bay and also have a similiar vintage AO Smith boiler - ours is 1972 for 1600 sf. My gas bill is very high -- $200+/mo average for 4 winter months - operates 120-180 hours/month during those 4 months and we never get it to "toasty" with (mostly) Italian tile floors (18" sq). I have the same issue as you in deciding to replace or not.
Replacing the boiler is like replacing your car (or similiarly replacing tires) -- you need full functionality, but it really depends on how long you're keeping the the appliance. A boiler has a 30+ years (hopefully) lifespan so are you buying it for you or the next owner ??
Using $5,000 for a new, fully installed boiler with decent efficiency, the PV cost is about $250 per year -- strictly as a financial decision, you need to determine whether you'll get $250 of value (lower gas and maybe "fuller" heating) during the 5-10 years of replacing earlier than necessary. An old boiler also has the cost of maintenance (like cleaning the heat exchanger). Like a car, I'll keep it running until I'm emotionally fed up or just want something new or different.

(2) The other question you seemed to have asked is Tankless hot water. Consumer Reports had a short article on Tankless vs. Tank in 2008 -- the payback I think is 10+ years and "unlimited" hot water had some hicupps. The report was unclear to me in a significant way -- an upper end tank can last 10-15 years) compared to a tankless 20 years (?? -- but need mineral cleaning if using unconditioned muni water) - - the comparison considered initial & annual operating costs but did not seem to factor in the lifespan annual cost (like a longer life light bulb vs. standard). In CR's opinion, the choice was not a slam dunk. Also, several years ago, I also read in CR that a larger water tank (e.g., 50 gal. from 40 gal.) does not significantly increase operating cost -- initial cost is higher but keeping 50 gal. hot vs. 40 gal. won't kill you in heating cost.

(3) The 3rd question you may have asked is whether to do tankless for both heating & water or a combo boiler for heat/water. There are several postings on this -- I like them separate just to reduce the concentration risk due to mechanical breakdown or natural disaster -- at least I'll have one of the 2 systems working in most circumstances.

Joined: Jun 12 2005

We recently installed two takagi units, one for heating and one for hot water.
We could go with a combination unit, but two takagi units were significantly cheaper than
one combination unit, and as previous post mentioned,
we didn't want a single mechanical failure to put us out of both hot water and heat.

Installing two units this way has its drawbacks. The installation costs double, which wiped
out our savings on the takagi units, and gas line upgrade is quite expensive as well.

It may be different for your case, but
our water heater and boiler are located indoor in our E-111 house,
so we preferred to have water heater that has direct vent.
This requirement narrowed our choices of water heaters, and
we had to upgrade our gas line anyway, since the existing gas line was not
enough to support even a single takagi.

For radiant heating using flash water heater,
we received most of our information from a radiant company in Vermont.
We had to customize a few components in order to support the required flow rate for our house,
and we are still trying to optimize the system. We decided to do the system design
and customization ourselves since there are many differing opinions
on the subject of using flash water heater for radiant boiler.

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