Power-vented water heaters -- what say you?

November 4, 2009 12:35 PM

Replacing a water heater... to power-vent or not to power-vent? That is the question.

Old water heater (possibly as old as 18 years) is leaking and will go away soon. It's currently chimney-vented; I'm pretty sure the chimney has a liner, but I don't know much about its size (so it's hard to tell if the current venting is effective at venting the heater's output). The furnace no longer vents to the chimney. This has all been unchanged for the past 7 years and there have been no problems, no carbon monoxide alarms aboveground, etc. The house is old and the basement windows (most windows, actually) are far from airtight, so there should be sufficient drafts for convection.

Plumber is recommending a power-vented heater instead of ventung the new one throughy the chimney too. His main argument is that as houses get tightened up and more airtight, chimney convection gets much less effective.

We're probably moving out of the house in the next 5-10 years and don't currently plan on doing an energy audit / making the house more airtight / replacing the basement windows etc in the meantime.

Plumber's quote is $800 for straight replacement with a new chimney-vented heater); $1500 for installing a power-vented one, setting up the venting, etc.

What experiences do you all have with power-vented heaters? Pros and cons? Do you think it's worth doing in this case? And is the cost differential (and the actual amount quoted) reasonable?

Thanks, hive mind!

posted by sesquipedalia to home & garden (15 comments total)

Going with a power vent water heater will let you get rid of that chimmney should it ever be a practical thing to do. Will you need to re-roof your house before you sell? If the chimmney was no longer in use it would be a relatively simple thing to take the top off and seal the old roof opening (something that I recently did when I switched to a direct vent tankless water heater)

I would say that you can't really make the wrong decision here, I don't see how either choice could be a negative for you. The power vent model might be slightly more attractive to a future buyer, but I don't know if it'd be $700 more attractive.
posted by davey_darling at 1:02 PM on November 4

Is going with an electric water heater and eliminating the venting altogether not an option?

As far as what you should do...if the old heater was venting properly up the flue, the new one should do just fine. Since the new heater is probably far more fuel-efficient, you'll probably be venting less anyway.
posted by Thorzdad at 1:03 PM on November 4

That's ridiculous. Get a different plumber. Actually, his "regular" price sounds reasonable, but the "power vent" in your situation is the equivalent to an extended warranty.
posted by notsnot at 1:04 PM on November 4

$800 sounds high for a water heater replacement. $1500 should get you a demand water heater. I'd get another estimate.
posted by electroboy at 1:07 PM on November 4

Power vent! It is more efficient and you may be eligible for energy company rebates etc. The price for the power vent sounds about right to me. We just had one installed for $1,400. We also ditched the chimney and gained an extra four feet of counter space in our kitchen.
posted by caddis at 1:24 PM on November 4

f the old heater was venting properly up the flue, the new one should do just fine. Since the new heater is probably far more fuel-efficient, you'll probably be venting less anyway.

The more fuel efficient the worse the venting up the chimney. Efficiency essentially means making the exhaust colder (taking out more energy for water heating) thus making it less buoyant.
posted by caddis at 1:27 PM on November 4

Thanks for all the responses so far!

No plans to remove the chimney... it wouldn't gain us anything in the house, and there's a fireplace in the living room we'd like to keep.

The current heater has an energy rating (whatever the number actually means) of .61. I think current nodels are only a little better, and current power-vented ones all seem to cluster around .67. So better (and there's a small rebate from focusonenergy here in WI)... so not much more efficient.

One possible element of the $1500 is that all the venting has to be put in, going through the basement wall etc... I'd assume that would take a few hours to do right.

Tankless is an option too but not one we're too seriously considering -- owing to the basement's layout, it would mean running a gas line along the side of the house, putting the heater in a room we might semi-finish in a year or two, and as I understand it the technology is not quite as reliable yet. (I'm generally a late adopter. All of that work was quoted at $2300 (but the tax incentives take 30 percent off that, apparently).

Does power-venting mean that you don't have hot water when / if the power is out? How much of an issue is snowdrifts mounding up to / over over the vent? What's the noise level like on new models?
posted by sesquipedalia at 1:46 PM on November 4

It cost me $600 to have a water heater moved from a closet inside the house to an outdoor location, which freed up the closet for other use and makes venting a non-issue (the outdoor enclosure is vented.) You might want to consider that.
posted by davejay at 2:00 PM on November 4

Oh, I should note I'm in Southern California. You're in Wisconsin, and my idea would be painfully stupid there. Ignore me.
posted by davejay at 2:00 PM on November 4

Does power-venting mean that you don't have hot water when / if the power is out?

Yes, but there will be some hot water stored in the tank.

How much of an issue is snowdrifts mounding up to / over over the vent?

Not good. I would imagine there is a safety cut-off if the vent if blocked, but it couldn't hurt to ask.

What's the noise level like on new models?
They are pretty quiet but you can hear the fan kick on. It has never annoyed me, and I am easy to annoy in this fashion.
posted by caddis at 2:03 PM on November 4

I live in Madison, too, and have a power vented water heater that we are angling to replace in the next year or two.

If the power goes out, you will have whatever hot water is in the tank - but if the power goes out so does the water heater. The solenoid for the gas line and thermostat doesn't run on magic. ;-)

As for the snow mounds blocking the exhaust, they could theoretically pile up that high. They do at my house since the snow from the driveway gets piled up alongside the house. So, we have to make sure to keep them clear. That said, it's a good 2.5 -3 feet up off the ground so it's not that big a concern unless we get lots of snow - it's not going to happen overnight. Frankly it takes more far more effort to walk the garbage to the curb.

We looked at getting an on demand heater. As hard as the water is in Madison, it's best to avoid them for the time being, I think. They calcify pretty quickly from what people who have them tell me.

The prices you have been quoted for the work don't seem out of line to me (kinda low actually), given what we've gotten for quotes.

You'll want to put some effort into isulating the basement more, you'll see big heat cost savings there. But don't make it airtight. The former owner of my house did and had to replace the blower motor 4 times in 9 years because they kept overheating and burning out.
posted by Pogo_Fuzzybutt at 2:39 PM on November 4

$600 for 60 gallon gas fired hot water installed here, near Philadelphia. Chimney vented. My understanding was that once the chimney was lined, you were OK. My gas fired heater also vents into the chimney, which I guess creates sufficient draft. I thought one of the main reasons for lining was to prevent the mortar from degrading. If there is not suffieint heat/draft, it creates too much moisture? Condensation inside the chimney? If the current heater is not vented through the chimney (high efficiency? it vents using PVC pipe?) why not vent the water heater the same way?
posted by fixedgear at 2:59 PM on November 4

I've heard the power vented water heater don't last as long. You'll notice at the 'Depot, they'll have a variety of regular water heaters rated for various life spans, and a single power vent model rated for 5-8 years. So you'll pay more initially, and have to replace it sooner. Maybe the fans burn out? If you've got a working chimney vent, I'd use it.
posted by Bron at 5:30 PM on November 4

Don't forget to account for gas savings on the power vented one.

I would go for the power vented one, for the following reasons:

1- You don't know the condition of the chimney liner. After three months of the colder, wetter exhaust, it might turn to mush. The more efficient the WH, the cooler the exhaust, which means the more likely it is to lose draft and/or condense inside the chimney.

2- It saves energy.

3- It is cool, fancy space age technology.

4- It *may* have various modes of operation like the newer furnaces do- running on half-duty when it can, and full blast when it has to.

5- I can't think of a reason why a power vented WH wouldn't last as long, but I have no experience with them.

The price difference seems a little steep, maybe you can DIY some of the work to cut the price down.
posted by gjc at 8:18 PM on November 4

With regards to snow and side venting, in Western Massachusetts the snow piles up a couple feet per year. The side vents have enough heat in the air to melt everything away around it. It's never been an issue.
posted by plinth at 6:16 AM on November 5