Tankless Hot Water Heaters (specifically gas)

[beelzerob]

I found an old old thread by Squintz looking into going tankless, but he was talking retrofitting old construction, and going electric.

I'm coming to the end of new construction on our house, and having now talked to the propane guy, of course he sang the merits of a tankless propane water heater. I had investigated this before, but the high initial cost put me off. Now, I'm considering it once again, and just wondering if anyone had any input one way or the other on a tankless hot water heater, but specifically a gas one, since I wouldn't bother with an electric.

The advantages I see besides monthly savings are also that it would be trivial to add to our generator subpanel, which means we'd have hot water for an extended blackout.

Can anyone give me anecdotal evidence of conclusive energy cost savings?

'Tanks!

 

[brotsten]

I found an old old thread by Squintz looking into going tankless, but he was talking retrofitting old construction, and going electric.

I'm coming to the end of new construction on our house, and having now talked to the propane guy, of course he sang the merits of a tankless propane water heater. I had investigated this before, but the high initial cost put me off. Now, I'm considering it once again, and just wondering if anyone had any input one way or the other on a tankless hot water heater, but specifically a gas one, since I wouldn't bother with an electric.

The advantages I see besides monthly savings are also that it would be trivial to add to our generator subpanel, which means we'd have hot water for an extended blackout.

Can anyone give me anecdotal evidence of conclusive energy cost savings?

'Tanks!

I installed both a tankless propane unit and an electric hot water tank. I have a semi-detached garage, with living space + bath above. The upper floor is connected to the main house via a breezeway.

In our situation, the water is rarely used in the garage/above living space. I installed the tankless unit in the garage.

We wanted hot water circulation in the main house, so we installed the electric storage tank.

My wife builds custom homes, whenever I brought up the tankless issue she replied that most of her customers who installed them were not happy with them. Typically flow issues. Washington state has fairly cheap electricity, when I did the cost comparison of the tankless propane vs the electric storage unit in operating costs only, electric storage was cheaper for us (not accounting for the recirculation).

I had the plumbers setup a crossover between the tankless and storage tank. In the case of a power outage, I twist two valves in the main house and the tankless units provides hot water for both sides.

Armed with the correct information, you can decide for yourself here.

As far as luxury goes, I had a hot/cold mixer spigot installed on the garage, man is that nice in the winter.

Brian

 

[politics123]

Why are you doing this? Energy savings is only one of the reasons to buy a tankless system. The other two (frankly, more compelling) reasons: (1) unlimited hot water without any recovery time (2) space savings -- there's no tank to eat up closet space. The first is nice if you like baths, or have a jacuzzi, etc. The second is hard to measure actual savings. 9sqft is about $1k of savings (@$133/sqft), but you'd only really see that if you were able to dramatically reduce the size of the house.

Assume you need XYZ gallons of hot water per day. You're going to pay to heat that up with or without a tank. The only real difference is that a tank system burns gas to keep the water at 120 degrees, even when you aren't using it. Modern tanks are pretty good insulators.... and you could approximate the cost savings by just using a plain-old-vanilla water heater, shutting if off when you aren't using hot water, and turning it on a few minutes before you need it.

If you want to explore "cheap" hot-water (cheap being ongoing operational costs), If you can afford it, the ground source heat pump option (with a desuperheater for H/W) is about as low-cost to operate as exists. High up-front costs, very low operating costs for life.

My story? I decided I wanted to save money and help the environment. I built in 2006, considered tankless, and instead installed Solar. $3800 after the tax credit, system is sized to cover about 85% of my hot-water needs.

 

[RobWalker]

We considered tankless, but ditched the idea. The only people I could find that were really happy with them were the sales people ...

For us the main drawbacks were:
1. flow rates
2. start up time

Here the (well) water in the middle of January is not very far above freezing (or at least doesn't feel it!). Most of the literature I saw talked about a delta-T increase. The colder you start the colder the output is going to be for a given flow rate.

I also didn't like the idea that the unit won't turn on until it hits a minimum flow. This can only increase the time it takes to get hot water out of the tap.

I think there are uses for these units, but providing whole house hotwater to a reasonably sized house isn't one of them (especially in cold climates).

We went with an indirect storage tank since we have a boiler for heating purposes. So far this has worked out really well ... except for the code mandated mixing valve which reduces out 'hot' water to 'tepid' for our own safety!

It a second heat exchanger for solar which we might add in the future ... but again in the frigid north I'm not sure of the benefit - we use most of our hot water before and after dark for too much of the year!

 

[beelzerob]

good input, all...and thanks!

Operating costs are a concern. PA electricity isn't very cheap, and from what I understand, they're about to deregulate it, and so far it seems to have the air of an electric bill horror story.

Space isn't a concern...we've got an 1800 sq ft basement, and any tank water heater won't fill up the alloted "mechanical" room space.

Hot water abundance is a concern. We're only a family of 4 (so far...), but there exists the possibility of my folks coming to stay with us for some unspecified amount of time within a year of movein. Also, my wife and I do love our long showers. In fact, our shower room has 2 shower heads, a his and a her's. So as it is, I was planning to install an 80 gal water heater, just to make sure we had enough.

Emergency use (as I mentioned) is also a concern. We'll have a generator subpanel and we'll buy a small, portable generator big enough to run essentials....which probably wouldn't include a tanked hot water heater, but a tankless wouldn't be a problem at all.

I haven't heard any complaints about the hot water being slow to come on with a tankless. We're farther north than some, and the ground water is definitely cold, but not near freezing. I also haven't heard of that being a problem with getting hot enough water out of it.

Geothermal, though it's the greatest thing since sliced bread, just isn't going to happen for us at this time. Probably same with solar...too much unknown there.

 

[123]

FWIW, three years ago I into our current home and immediately had to replace the gas-fired water heater (storage tank). After examining tankless units I opted for another gas-fired, storage-tank heater. The water-flow issue plus lousy ROI axed the tankless option. 40 gallon unit for $300 and I installed it myself.

 

[Ranger Digital]

I dont get the cost issues. Tankless can be had under 500 bucks. Tankless increases "X" degrees so it only makes sense the colder the input the less hot the output. as opposed to heating a tank to X degrees.

Beez, i too have not heard of all these issues. All the higher end homes here in texas get tankless. Never heard one complaint. Opposite actually about how fast and abundant hot water is and how the electric bill DOES reduce. Many put small tankless under a very used sink or in a bathroom for even more instant.

Go figure.

 

[brotsten]

Beez, i too have not heard of all these issues. All the higher end homes here in texas get tankless. Never heard one complaint. Opposite actually about how fast and abundant hot water is and how the electric bill DOES reduce.

Assuming they replace an electric storage tank with a gas tankless, I'm sure the bill goes down.

Brian

 

[beelzerob]

That's the 2nd time I've heard of a lousy return on investment for a tankless water heater, and I'm not sure what you mean by that. Are you specifically meaning as far as house resale value? Or are you talking quality of hot water? Or do you mean that where you live, the operating cost savings are insignificant enough that it'd take much too long to pay off the difference?

 

[rwdozier]

I found an old old thread by Squintz looking into going tankless, but he was talking retrofitting old construction, and going electric.

I'm coming to the end of new construction on our house, and having now talked to the propane guy, of course he sang the merits of a tankless propane water heater. I had investigated this before, but the high initial cost put me off. Now, I'm considering it once again, and just wondering if anyone had any input one way or the other on a tankless hot water heater, but specifically a gas one, since I wouldn't bother with an electric.

The advantages I see besides monthly savings are also that it would be trivial to add to our generator subpanel, which means we'd have hot water for an extended blackout.

Can anyone give me anecdotal evidence of conclusive energy cost savings?

'Tanks!

I am a builder in West Texas and have installed gas tankless water heaters in almost all of our homes. No customer call backs or complaints. I just think everyone should have one. I've been in our new 2500 sqft home (4 bdrm, 3.5 bath on slab) for over 2 years and absolutely love our unit. There is no circulating loop and it takes only about 3 minutes to get hot water to the master shower (heater about 35' away) - about the same as a tanked unit. When we have a family gathering with all the kids and grandkids, we always have hot water! The unit for this house is the Noritx 0751 series. (http://www.noritz.com/homeowners/products/view/0751_series/) For larger homes that I build (3000 sqft or more), I install the same unit with an insulated circulating loop with UPB smart switches in each bathroom to turn on a UPB smart receptacle at the water heater to turn on the circulating pump. An Aqustat turns the pump off when returning water in the loop reaches a set point of 100 degrees. The smart receptacle only stays on for a set time of say 20 minutes. The setup prevents running water down the drain until it heats up the point of use if it on the opposite side of the house. Should you ever need more demand, these heaters will work in multiple setups all linked together. I know this does not address any specific energy cost savings - all I know is that when the hot water faucet is turned on in my house, I have hot water, then and only then. When I leave my house, there is not a tank of hot water just sitting there being kept hot. Bottom line I say is this: if you can afford the upfront cost, just do it. You'll be glad you did. ...Bob

PS. Be sure to follow the manufacturers specifications for gas or propane supply. Plumbers will attempt to install a 1/2" flex line to the unit. You need a 3/4" supply line (gas or propane) all the way to the unit for proper operation.

 

[Steve]

There is no circulating loop and it takes only about 3 minutes to get hot water to the master shower (heater about 35' away) - about the same as a tanked unit.

And that is acceptable? So you have to wait in the shower with water running for 3 minutes before the water gets hot? Mine currently takes like 45 seconds and that is too long. During the bathroom remodel either going to put in a small 6 gal tank or a recirc system because even that 45 sec is too long.

 

[beelzerob]

There is no circulating loop and it takes only about 3 minutes to get hot water to the master shower (heater about 35' away) - about the same as a tanked unit.

And that is acceptable? So you have to wait in the shower with water running for 3 minutes before the water gets hot? Mine currently takes like 45 seconds and that is too long. During the bathroom remodel either going to put in a small 6 gal tank or a recirc system because even that 45 sec is too long.

I think that might have been an estimate or something...I also was astounded at 3 minutes, as 3 minutes is a long time, longer than I've ever had a shower take, no matter how far from the hot water heater it is. The key in what he said, I think, is that it takes about the same as a tank unit.

From everything I've seen and read, the time from water on to hot water coming out of the tankless unit is very fast...pseudo instantaneous.

 

[DavidL]

I put an electric tankless water heater in my barn. The unit was very reasonably priced, and so small I can't believe that it will actually work. I haven't tried it yet so I remain skeptical. It does take like 60 amps 220volts. The one I got has a flow sensor so that it won't turn on if no water is running. Probably to prevent a unit meltdown. My barn does have a shower, but I will be suprised if I ever use it with this heater. I did plumb the means to hook up a more traditional or gas fired heater, but for the current hardly ever need hot water for the barn, and mostly for washing hands, it will probably do just fine.

 

[rwdozier]

There is no circulating loop and it takes only about 3 minutes to get hot water to the master shower (heater about 35' away) - about the same as a tanked unit.

And that is acceptable? So you have to wait in the shower with water running for 3 minutes before the water gets hot? Mine currently takes like 45 seconds and that is too long. During the bathroom remodel either going to put in a small 6 gal tank or a recirc system because even that 45 sec is too long.

I think that might have been an estimate or something...I also was astounded at 3 minutes, as 3 minutes is a long time, longer than I've ever had a shower take, no matter how far from the hot water heater it is. The key in what he said, I think, is that it takes about the same as a tank unit.

From everything I've seen and read, the time from water on to hot water coming out of the tankless unit is very fast...pseudo instantaneous.

Yes, that was an estimate. Sorry, it just seems to take a very long time when you are waiting on it. I just tested it, all cold, heater not fired for several hours - 40 seconds for warm water, 50 for very warm, 55 I had to move my hand. And yes, if it were a tank heater, it would be about the same. Yet, a sink on the opposite wall from the heater, it gets very hot in just a few seconds. Regardless, endless hot water.

 

[DavidL]

My current electric 80 gallon tank has gotta take 3 min for a shower due to the long run. It's not really a big deal, just turn on the water, brush the teeth and jump in the shower. It's on a diagonal across and up the house so it's a very long run.