The math of tankless water heaters

[tensile]

I just installed a propane Bosch tankless in place of a 40 gal. Love it. I did have to run a HUGE gas line, the one for your current gas tank water heater will not cut it (that's according to the manual...I didn't have an existing gas line, so I just used the size recommended in the manual). I used the corrugated stainless pipe, very easy for the average DIY as far as gas lines go. My electric bill dropped by 1/3. I had to use the blower-powered horizontal vent, which required some serious fabrication. For DIY, in place of an existing electric unit, my total for the install, including the heater came to about twice the cost of the heater or $1600. For me, this means the payback is 32 months; this includes the increased propane usage, but does not include the sweet rebate from the power co (no inspection required).

[BSS]

For those who are interested, I installed the 7.4GPM Paloma tankless unit on July 20th. My billing period ends on the 5th of the month, so half of the month was with the old tank and half was with the new unit FWIW.

MY PROPANE BILL WAS $12.76.

And that's only a half of a month. Granted it is the middle of summer, but in the five years I've been in my house, the next cheapest bill I've ever had was $38.00. I seriously can't believe it.

[OSECS]

Nice BSS !!



So just how DIY is this little project ?? I've tackled a lot of shit in my day. Messin' with gas skeezes me out a little. We've got a 50 gal. gas fired tank in the laundry room now.

One other question, anyone use a recirculation pump in conjunction with these units ??

[BSS]

Just remember to turn the gas line off before you start and you'll be fine.

I'd say this is about a 6/10 on a scale of mechanical ability. 1 being hanging a picture frame and 10 = building a house. If you can freehand mount a set of ski bindings, you can install a tankless water heater. Plus the directions are very thorough. Run 3/4" id yellow flex gas pipe and Sharkbite water fittings/pipe from your existing metal hot & cold terminations and you'll be stylin in like 2-3 hours. I don't have a recirc pump, but then again I have a small house and it's just two of us so not really necessary. I'd say put in the heater then go from there. You can always add one later if you determine it's necessary.

Don't forget a sediment trap for the LP line
Use a new T&P relief valve on the HW out
ONLY use UL cat III stainless vent pipe
easy

[uglymoney]

For those who are interested, I installed the 7.4GPM Paloma tankless unit on July 20th. My billing period ends on the 5th of the month, so half of the month was with the old tank and half was with the new unit FWIW.

MY PROPANE BILL WAS $12.76.

And that's only a half of a month. Granted it is the middle of summer, but in the five years I've been in my house, the next cheapest bill I've ever had was $38.00. I seriously can't believe it.

That is awesome.

My gas bill last month was $19.26. I have a tank water heater, gas grill, and gas dryer and we grill 3 nights a week at least.

Even if the payoff might be forever for me, I'm still becoming sold. The tank in my basement takes up a tremendous amount of room in addition to being inefficient. Payoff, trade off. Looks good.

[moose pit]

Nice BSS.

[tensile]

...
One other question, anyone use a recirculation pump in conjunction with these units ??

I seem to recall from the manual that recirc pump plumbing can get a little tricky. My igniter is fired by a water-driven generator (no flow, no fire). The manual said that a recirc pump would require a storage tank and checkvalves to prevent back feeding the tankless. For awhile, i used a 2.5 gallon electric located at the shower for instant hot water. By the time that was empty, the hot water had arrived from the tankless. since the water in the 2.5 was already hot, the 2.5 gallon tank only had to keep it warm, which means it didn't use too much electricity. After a few months, i decided i could live with waiting 15 seconds for the water to heat up and ditched the small tank. I also have a small house/short pipe runs, so YMMV.

[MontuckyFried]

Thought I'd bump this since I'll soon be in the market for a new water heater. The house I just bought has the original water heater (10 years old), so it's overdue to break with the water around here. Looks horrible and doesn't work so hot, so I'm assuming it's chock full of minerals like my other 10 year old heater down the road was. Was a nightmare when that pos broke!

I've always wanted tankless but never had a place that could really justify the higher cost until now. Anyhow, the main reason I'm bumping this thread is because I'm wondering have costs come down much over the last few years? Please tell me they have, so I can convince my wife to get on board with it. Haha.

Has the technology changed much too?

[Cruiser]

I'm in the same boat. The water heater here is likely on it's way out and I would really like to go tankless. We had tankless when I was a kid and it was fantastic even back then (>25 years ago). But it's hard to look at the expense of plumbing, ducting, and the unit itself without getting a little concerned that I'd be making a big mistake. I can do a fair amount of the work myself, but I could pop a replacement tank unit into the spot that I pull the old one from in a matter of a couple of hours on a Sunday whereas I'd be spending all day trying to sort out retrofitting a tankless unit.

[1080Rider]

I've been told that the water in my area (eastern, WA) is too cold and that the water will never get really hot, just luke warm in the winter. Does that sound right? I see that a few people have them in areas colder/just as cold as my location. What are your thoughts?

[Moeghoul]

I've been told that the water in my area (eastern, WA) is too cold and that the water will never get really hot, just luke warm in the winter. Does that sound right? I see that a few people have them in areas colder/just as cold as my location. What are your thoughts?

We have one in N.VT, (well) water gets hot, but you need to let it run for a while as in turn the hot water on in the shower and then go brush your teeth or do something else for a few minutes.

[MontuckyFried]

Hmm. I might want to rethink it then. My local water can come in pretty dang cold sometimes. Like 45 out of the tap. Makes for awesome drinking water, but sounds like a tankless water heater might have a tough time catching up. Also don't like that it takes so long to deliver it to your faucet initially.

I might just go with a somewhat higher-end tank, then.

[Moeghoul]

It's a minor annoyance that we didn't realize until after we got the house, but the water runs hot and it doesn't run out. Since we are only up there 1-2 weeks a month, I'll take the savings not heating water 24/7. I think its a function of distance from the heater to the faucet/appliance.

[Arty50]

I think its a function of distance from the heater to the faucet/appliance.

That's definitely the case. The faucets near my unit heat up really quickly while the faucets on the other side of the house take a couple of minutes. Tanked houses aren't that much different. A little faster, but not necessarily.

[plugboots]

I've been told that the water in my area (eastern, WA) is too cold and that the water will never get really hot, just luke warm in the winter. Does that sound right? I see that a few people have them in areas colder/just as cold as my location. What are your thoughts?

This is not true. We live in Eastern WA and our water comes from a well, and you can set the instant on for whatever temp you like within reason. Incoming temp is a non-factor.

[old goat]

We live in Truckee. We have a 199,000 BTU tankless water heater--a Navien. No problems with getting hot enough water, or enough hot water. The unit is much larger than others I've seen. The wait at fixtures near the tank is no problem. Only the kitchen is a problem--when the new heater was added as part of an addition the hot water pipe went to the old system, doubling the already long run. The furnace was in the way of a direct line--when we replce the furnace we'll run a direct line.

I have a question--we have a house in Sacramento that sits empty most of the time with a 25 year old gas tank water heater we need to replace soon. The house was built in the thirties, with galvanized pipe in the original house and copper (with dielectric fittings) in the upstairs addition. I've been told you can't use a tankless heater with galvanized. I assume the water main in the street and the line from the main to the house are galvanized. We could run a copper line from the main valve to the new heater, but there would still be galvanized coming to the house. Is there any kind of filter that could be used to protect the heater from the crud in the galvanized, which I assume is the problem.

[iceman]

What, like particles of zinc? There are sediment filters you can get, I have one and it works like a champ, but it seems odd that that would be a big problem.

[runethechamp]

I've had a tankless water heater for 6 or 7 years with galvanized pipes with no problems. I'm pretty sure there is a simple mesh filter on the intake side of the water heater that will catch most particles coming from the pipes.

[Tuckerman]

Have you looked at heat pumps?

[Danno]

nobody cares about heat pumps

[SB]

Many tankless units are recommended to have a corrosion protection device installed inline to help the longevity. Whole house filters are a good idea also. Navien is the best I have looked at.

Plus the incoming temp of the water makes a big difference, they can only heat the water up so much. More BTU size is of course better fro this.

The small point of use electric water heaters make the most sense for vacation condos or remote locations.

[old goat]

Many tankless units are recommended to have a corrosion protection device installed inline to help the longevity. Whole house filters are a good idea also. Navien is the best I have looked at.

Plus the incoming temp of the water makes a big difference, they can only heat the water up so much. More BTU size is of course better fro this.

The small point of use electric water heaters make the most sense for vacation condos or remote locations.

I don't think incoming water temps get too much colder than we have in Truckee--our Navien 199,000 has had no trouble heating to 130 in the winter. These things probably don't pay for themselves unless they're in a house that is unoccupied a lot, but if we all had one maybe the snow level would come down a couple of feet.

[AdironRider]

My inlaws are way the fuck up in Northern Maine, and just installed a tankless water heater last fall.

They initially had a bit of a warm up issue as well, but also have a woodstove. They ran a waterline through the woodstove to prime the temps prior to hitting the water heater in the winter and solved that problem.

Now they already had the stove setup in the basement, so it was like 20 bucks and an afternoon of DIY to make that work, but could be an option for you as well.

[Rideski]

The question of gas tankless water heaters working without electricity has come up a few times, maybe in the home improvement thread. I was pretty sure mine ran without, but hedged my bet till the power went out to test. My unit for sure heats without electricity, and I don't think it has a battery either. That said, I don't know how that happens. Maybe a mechanical level that moves with water flow and engages a solenoid? There's absolutely no Romex going to my water heater.

With all that in mind, perhaps entirely coincidentally, the power went out last night, and I was using the hot water. And then an hour later it stopped heating. Now the power is back on, and still no heating. The pilot light is on. A little googling mentions a solenoid, but not sure mine would have one considering there's no electricity. Wouldn't be the end of the world to replace it and upgrade, but kinda bad timing for a variety of reasons.

[old goat]

Ours definitely doesn't work without electricity. It plugs into an electrical socket. It has electronic ignition. It's hard for me to understand how one could run without electricity but I'm no expert. If you have a back up battery or generator a gas tankless would certainly use less electricity than an electric WH.

Re the math--our LEED-certified architect friend feels that for a usually-occupied house tankless WHs offer minimal energy savings compared to an up-to-date energy star ranked conventional, with a very long payback period. He feels the money is better off being spent elsewhere. And he is the guy who designed a bathroom addition with tankless water heater for us--at our request.