About to pull the trigger on a tankless water heater.

[teacherman]

Hi everyone,

If this topic has been beaten to death somewhere, I apologize. Please direct me if so...

I am replacing my old fuel oil furnace and electric water heater with a natural gas. My HVAC guy quoted me $1800 for a direct-vent HE tank water heater or $2200 for a Navien tankless unit. I am pretty handy and have done research on this site and others and about to pull the trigger for the Rheem RTGH-95DVLN (using MMM promo code at GPconservation.com--thanks Mr. Money Mustache!) and will install it myself.

Any advice or experience anyone want to share before I purchase?

Thanks!

[Spork]

This is based solely on my experience and I have no real data to support me at all.  There: caveat in place.

I have a tankless.  I actually like it.  ...but I'm just not convinced it saves money (or if it does, it is going to take me many years to recoup it).  They can be quite the luxury item -- never running out of hot water ever -- but if you're lingering in that hot shower, you're burning up gas.   

It's "more efficient" because you don't run it much and because you run it at a much lower temperature than a tank heater.  (Remember: you have infinite hot water.  Tank heaters are kept hotter because they're constantly being diluted by cold water.)  But if you're running it at 140 degrees or running it off and on all day long (as the last MMM article suggested) I am skeptical that there will be any savings at all.  The first month we had our tankless set up we ran it at 140 degrees (dumb) and only used it for showers, dish washing, etc.  We used 250 gallons of propane that month.  Turning the dial back to 120 makes 250 gallons last > 6 months.

I know nothing good or bad about the Navien you were quoted... but $1800 sounds like a whole lot for a tank heater.  Is there a lot of work that needs to be done to bring it up to code?  (The last time I had someone put in a tank -- AND bring it up to code -- I paid $800 for the whole thing.)

[Greg]

Don't get more on-demand than you need.  Smaller units for 1-2 bathrooms are more efficient than the larger ones that are sized for larger houses. 

There are two reasons tankless heaters can be more efficient.  One is they don't heat water unless you're using hot water from a faucet or appliance.  The other is that they only heat the water as much as you set it for, meaning it's a variable output burner.  This heater is 199K BTU max input so make sure you pipe it for that possible demand.

For comparison, my Rinnai is 185K BTU and it supplies 2 baths, a kitchen, our radiant heat.  One nice side effect is you can fill a hot tub, that's the endless hot water thing working in your favor.

[Sparky]

I feel there might be more going on than just a tank heater if its 1800 bucks.

Hot water tanks are really easy to install if you've already got the gas line and water lines in place. Did my last one in about an hour….

[NinetyFour]

I have a NG one and I love it (it's a Bosch Aquastar).  I do not linger in the shower.  I use hot water only for showers and doing dishes in the cold months.  Also, I do not shower at home on workdays.  So I really don't use much hot water at all.  It would be silly to be keeping a whole tank full of water hot 24/7 when I use so little of it.

Good luck with the installation!

[TravelerMSY]

I'm interested in replacing two aging tank hot water heaters in an upcoming renovation, but I'm stuck on the fact that the gas models don't work when the power is off, unlike a gas tanked heater. And it comes up pretty often in my neighborhood of New Orleans.

On the other hand, the water comes out almost warm enough to shower in unheated during summer hurricane season.

[Spork]

I'm interested in replacing two aging tank hot water heaters in an upcoming renovation, but I'm stuck on the fact that the gas models don't work when the power is off, unlike a gas tanked heater. And it comes up pretty often in my neighborhood of New Orleans.

On the other hand, the water comes out almost warm enough to shower in unheated during summer hurricane season.

*IF* that is your only concern... *AND* you have a freezer... consider a small generator.  The power required is minimal.  It just has to spark the gas jet and open the solenoids.  You could probably even run the water heater off a very small UPS if you really wanted to.

[southern granny]

I have never had one, but I talked to a plumber once who told me that he wouldn't have one and that most of his customers who did, went back to a regular hot water heater when it had to be replaced.  He said he had never installed a second one for a customer.

[Greg]

I'm interested in replacing two aging tank hot water heaters in an upcoming renovation, but I'm stuck on the fact that the gas models don't work when the power is off, unlike a gas tanked heater. And it comes up pretty often in my neighborhood of New Orleans.

There are models with battery-powered ignition and no A/C needed.  Bosch AquaStar was one 10 years ago, I'm sure they still make them for use in remote locations.  Might not meet code in your area.

[TomTX]

I'm interested in replacing two aging tank hot water heaters in an upcoming renovation, but I'm stuck on the fact that the gas models don't work when the power is off, unlike a gas tanked heater. And it comes up pretty often in my neighborhood of New Orleans.

There are models with battery-powered ignition and no A/C needed.  Bosch AquaStar was one 10 years ago, I'm sure they still make them for use in remote locations.  Might not meet code in your area.

Wasn't battery, there was a Bosch which had a microturbine in the water, so water flow generated the electricity for the spark. Really quite a nice concept.

[Greg]

My AquaStar does have a battery ignition, so maybe there were a few different versions.   :)

2 D cells, that last about a year.  There's a slight delay as the safety pilot lights, then the burner, but it's not a huge difference compared to the Rinnai we also have.  Our AquaStar is in the garage.  It's kind of the best of both worlds, no standing pilot (using a fair bit of fuel) but also works when the power is out.  As long as the water pressure lasts.

[Spork]

My AquaStar does have a battery ignition, so maybe there were a few different versions.   :)

2 D cells, that last about a year.  There's a slight delay as the safety pilot lights, then the burner, but it's not a huge difference compared to the Rinnai we also have.  Our AquaStar is in the garage.  It's kind of the best of both worlds, no standing pilot (using a fair bit of fuel) but also works when the power is out.  As long as the water pressure lasts.

Holy moly.  When I said "small UPS" ... I had no idea how small.   I knew they didn't pull much.  Ours runs off a 15a dedicated circuit -- but I think that was done more for generator breakout than because it requires 15a.

[TravelerMSY]

Battery backup would solve my problems completely. Thanks! Didn't know they even existed.

[Greg]

A quick google search shows the battery ignition model isn't in production anymore but the hydro-ignition one is.
http://www.tanklesswaterheatersdirect.com/shop/bosch/bosch-tankless-water-heater-520-hn-gas.asp

[DollarBill]

The one thing I've been warned about is the flow rate. If you have a high flow rate then you will have a cooler temp at the shower head. So if you have multiple people in the house you will notice the temp change.

[teacherman]

Well I decided to buy the Rheem RTGH-95DVLN Natural gas tankless water heater. I will be installing it myself when it arrives next week. I will update if anyone has questions about how the install went and if it seems to be useful. Thanks for the responses!

[Cromacster]

Just had a question about the install.

Do people here suggest doing the NG plumbing yourself?  Is NG plumbing a DIY project?

[Spork]

The one thing I've been warned about is the flow rate. If you have a high flow rate then you will have a cooler temp at the shower head. So if you have multiple people in the house you will notice the temp change.

sort of.  The important thing is to match the flow rate you want with the flow rate of the water heater.  Higher flow rate heaters equate to more expensive heaters.  Most folks that complain about it not heating enough just didn't buy enough rate (or they have too high a flow rate on their shower heads). 

[Greg]

Do people here suggest doing the NG plumbing yourself?  Is NG plumbing a DIY project?

If you can apply pipe dope and turn a wrench, you can probably do it.  You must test for leaks with soapy water.  Find a leak, backtrack and fix it.  It's not rocket science but if you don't test for leaks and fix them things can blow up just like in rocket science.

[teacherman]

FYI, I'll be having my HVAC guy do the NG plumbing. He is installing my furnace and running a gas line to the outside hookup anyway.

[bacchi]

What's the going price for a tankless install? I received a bid for $3500, which includes $1300 in "additional materials." That's a lot of padding.

[Greg]

What's the going price for a tankless install? I received a bid for $3500, which includes $1300 in "additional materials." That's a lot of padding.

Maybe... there's the water heater which maybe isn't in your quote.  But the quote has to include the coaxial flue pipe, the valve kit, and any adaptations that need to be made.  If it does include the water heater it's much more reasonable.