Tankless Water Heaters

[96Pirate]

My 10yr old 50 gal tank is on its last legs. For the better part of 5yrs I've had on my mind that I would replace it with a tankless water heater. So I am early in the research process and wanted to see if anyone has opinions. I started briefly looking at the Rheem and Jacuzzi brands from the 2 big box stores this weekend.

Home specs...Family of 4 (2 adults, 2 girls...8&10...so long showers will be coming), 4Br, 2 1/2 bath, 3000SF, Natural Gas

I am a DIY'er so will be planning to do the install myself except for moving the gas line.

Does anyone else have one? Likes/Dislikes? Brands? Indoor/Outdoor Model?

Anything else you can offer will be greatly appreciated.

Thanks

 

[sysinu]

If I read this right, you just want to know about gas tankless heaters.

I am currently thinking about what's going to happen to my 40 gallon tank as well and I have talked with a bunch of people and I am getting really mixed reviews on tankless gas water heaters. Most people swear by them. I think the tipping point would be what kind of water pressure you want to get. Gas tankless get up over 8GPM (but then they get really expensive). You can get a pretty good Rheem electric tankless heater that's 5GPM for a really low price (the ones I have looked into on Amazon are heavily discounted).

I have 3 adults and 3 kids in my house, split between levels and the similar 2.5 bath configuration. Right now, I'm thinking about going electric and putting one to feed each floor. I don't think I need 8GPM worth of water pressure, and 5 should be more than enough. I know it's more $$ to heat the water electric vs gas, but I think between the cost of electric vs gas heater it would take a long time to pay for the difference between the two and for me, splitting the use between the levels makes a great difference when you're talking about having 3 showers running at the same time.

 

[dan144k]

Pay attention to the flue pipe material needed for the tank-less system.

I recently install a commercial unit for work was like 400,000 BTU and it needed to use special flu pipe.

Most of them require specialty flu pipe which can get expensive, and cannot go into chimney
If I were to put one in I would make sure it uses a PVC flue pipe (PVC also means the Higher efficiency unit)

Also pay attention to the efficiency. Several on the market are only 80% or 85% but say HI Efficiency all over the box.

Also note that the capacity is dependent on your incoming water temp.
For example I live in Chicago summer 70 degree water and winter 35 degree water, It makes a difference how many BTU you will need.

Another consideration is how many people shower at the same time, and family water use patterns.

About five years ago I installed a instant water heater/boiler combo. We added a storage tank and small pump, the customer wanted a recirculated loop so he would truly have instant hot water. The tank and loop pump always kept all the pipes hot (we may have put it on a time clock too). And when someone would turn on a faucet then the instant heater would fire up mixing with the storage tank (small electric heater). Worked well and he has been happy. Was very expensive.

Another thing to consider is if you loose power frequently; the basic water heaters will still heat without electric.

 

[jawsf16]

I have two electric tankless water heaters in my house. They are like a three car garage or sprinkler system, once you have them you will wonder how you lived without them.

That is all I know about them. They rock.

 

[Julian]

I have a Renaii (SP?) top of the line tankless water heater. I think it does something like 7.5GPM. We put it in when we had propane as our only gas source and were replacing two 50 gallon hot water heaters (in our crawl space). The first concern I had was the time it would take to get hot water - I'd read there was a delay. I was interested in the electricity and propane savings too. So we went ahead with it. I timed the length of time to get the first feeling of warm water to the tap in our Master bath (as far from the tank as possible). With the standard tanks it took 45 seconds to get hot water to the tap. Once we switch over to tankless it took 1:15, which as a percentage is a HUGE increase in time. So be aware of that.

Then of course, our local natural gas company FINALLY agreed to install NG in our community, so we switched it over to NG (make sure if this you plan to use propane that it is switchable to NG--some aren't). This was great news in general, but it wrecked the ROI calculation on the tankless heater as NG is so much cheaper. I would have been much better off just buying a couple of standard tanked heaters.

 

[Andy S]

@96Pirate one thing my neighbor found out about his tankless heater was that with flow restrictors in shower heads and faucets when he wanted to take a shower he would also have to turn on the faucet to get enough flow for the tankless heater to fire off. Once he removed/drilled out the flow restrictors in the shower heads, he no longer needed to turn on the faucet to get hot water in the shower. This might not be an issue if you are on city water but my neighbor is on well water.

As for those looking to retrofit to an electric tankless, this could be an expensive upgrade. I have an electric whole house tankless heater that I installed during construction (no NG nearby and I didn't want to go with propane because at the installation time propane prices were way to volatile), so all the wiring and load was planned. A tanked water heater typically uses 1 - 40 amp 240VAC circuit whereas my electric tankless has 3 - 40 amp 240 VAC circuits feeding the unit, adding 2 additional 40 amp circuit could be expensive.

 

[txav8r]

I don't think many tankless units can meet the demand of jaccuzi sized tubes or custom shower heads...that are priced reasonable. I know reasonable is subjective, but it has to make sense for you. Also, they are designed to be point of use heaters, so trying to cover a whole house may be an effort if the house isn't designed for it. I know I have two 50 gallon heaters in mine, and it is overkill, but we don't run out of hot water. To replace what we have without a loss was going to require a minimum of 3 pretty large capacity tankless heaters, and one plumber speculated we might need 4 including the laundry room. Since our house is Geothermal HVAC, our compressor sections also have what is known as desuperheaters, and they recover the excess heat from the compressors before dumping that heat in the geothermal loop. Our hot water is essentially free 9 months of the year, so the cost advantage was lost when comparing tankless with standard electric water heaters. Another note, our house is 12 years old, and I am sure what is common today was uncommon 12 years ago. So it may be very easy to convert and gain a cost advantage. But the reason in my mind for tankless, is instant hot water. Without that, the savings is lost pumping hot water all over the house. Again, my findings may be invalid today.

 

[BigN8]

My version of instant hot water:
Wake up! stagger into bathroom.
Turn on shower to hot
Brush teeth at sink with cold
Take a shit
By the time I step into the shower, she's nice and steamy!
Oh, and I shave in the shower.

Pretty much how I can be ready in 10 minutes, and to this day I don't understand how it takes the wife 1 hour and 15 min

 

[txav8r]

ROFLMAO! I do the same, and also shave in the shower, thanks to a heated mirror in there! But I don't have instant, so it takes time...how long? I don't know, but less time that to take a $#!+! lol! I can pretty much turn it on, and brush my teeth, and it is hot. We have a PEX system with MANA BLOCK distribution like a service panel for water. We have two mana blocks and two water heaters. It probably takes less than 40 seconds to get hot water to any faucet. Admittedly, however, I am cheap like some of you...so I have my hot water heaters set to 125F, so my electric doesn't hardly ever run. It is plenty hot for anything we need. We have a Pure Wash system for laundry, so we use only cold water, and NO DETERGENT!

 

[Julian]

Our tankless Rennai 98i handles the whole house with no issue at all. Endless hot water. I had to look it up to check the GPM and it has a 9.8GPM max.

Another thing I've HEARD is that some tankless heaters need to be cleaned depending on your water quality.

At this point though....we are very happy with ours.

 

[txav8r]

So how does your Rennai do at supplying different areas of the house and what kind of delay do you experience @Julian ? I thought you said it took 75 seconds to get hot water? Any delay is a PIA, but some delay is understandable, even with "instant". Having two separate systems, we never worry about the kitchen or laundry running and the bedroom baths competing for the hot water. When I was researching, it seemed like this wasn't something tankless could handle. Has that changed? What would a washer demanding hot water, and the dishwasher or kitchen sink demanding it, along with a family getting ready for bed and hitting the tubs and showers? Again, I don't know because I don't have the tankless, but what I learned back 12 years ago was that a single tankless couldn't handle all of that, and that I needed two minimum. If your experience is better, that is good intel. On a comparative note...you supposed to clean the gas or electric water heaters too...how many do?

 

[96Pirate]

Hey thanks guys! And thanks for the laugh too.

I think they have come a long way in the past 5 years with these and they should be able to easily supply enough hot water for our needs. We have never had issues with our tank not supplying enough hot water. One of the reasons I am seriously considering one is the longevity of the units. At least the claims as I have not seen real numbers. The claims are that most of the better units will outlast a tank by quite a bit. With that plus the energy savings I think in the long run I would come out ahead. But that's a big ? I know one thing I need to consider is the BTU rating on my meter. I have not looked at it yet but if I need to upgrade it that might be expensive. Tankless have a lot higher BTU draw than Tank. I believe the units pushing ~8gpm would be enough for me but I don't want to undercut it so I am thinking I would go with the ~9.8. But still open to something less if I know it can handle our needs.

 

[96Pirate]

Ohh, and yes. I understand there seems to be longer delays in getting hot water with the tankless. I am going to test my tank tomorrow morning to get a real number on the current and then use as a comparison.

 

[Julian]

Ours can handle 3 large items running at the same time....like 3 showers going at once, or 2 showers and a washer etc. Our water pressure is more of a problem than the heaters capacity to warm the water!

My brother just installed a new HW heater in his garage and went with one that air conditions his garage while heating the water. He loves having a cool garage.

There are also hybrid HW heaters than have both a tank and tankless function and less installation requirements.

 

[Andy S]

My electric and my neighbors propane tankless, the only delay comes from the time it take water to flow from the tankless heater to the device. After initially installing my electric I had the wife turn on the shower, I felt the output of the tankless heater and water pipe was instantly hot.

 

[davel501]

As an investment, tankless water heaters are terrible. You could probably buy 3 tank water heaters for the same price. They do not leak heat into the hot water pipes in the house so the water may or may not be warm in the pipe depending on how long it has been since you last used it. You also will not save any money on gas because you never run out of hot water. There is, quite honestly, no good reason to get out of the shower. There are no standing pilots in my house so there is actually a savings when we go on vacation for a week.

Finally, and THIS IS A BIG ONE, the freeze protection on the Rinnai's only goes to -25. Not a big deal in most cases but thanks to the polar vortex I had to drain mine before going to bed about a dozen times last winter.

The trick with tankless is to measure your water temperature at the coldest point of the year. Mine, from my private well, is 53 degrees in late winter and doesn't get a lot warmer during summer. They have charts where you take the maximum increase in temperature and gallons per minute to arrive at the right unit.

Here is the parts list:
http://www.amazon.com/gp/product/B0058DQLPW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B004PYEAXK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B004PYEB9S/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

You will also need to upgrade your gas line (I had to go to 1-1/4") to get the amount of gas you need and that will probably also lead to needing a larger meter.

Total cost was $1500 with me doing all of the copper and gas pipe myself. Double that if you have to pay someone.

Here is the finished product (notice the 1" reducing to 3/4" gas pipe at the bottom left 90 - if you see a flexible connector going to a tankless water heater it is starved for gas):

 

[PEARCE]

Like Julian we have the Renni tankless water heater that runs on natural gas. It was an option that our builder offered when we had our house built in 2002. We love it because we can all take showers and not have to wait for a tank to refill. Our unit is on the outside wall to our master bath and closet so the master gets hot water almost instant. The kids bath is on the opposite end of the house and it can take a minute or two if there hasn't been any hot water usage in the kitchen or laundry room. The kitchen is in the middle of the house so it's about half way to the kids bath. There are circulation pumps that can be to the loop at the time install, but waiting has never been an issue for us. We make it a point to not be running the dishwasher or the clothes washer while people are showering because of water pressure and not the lack of hot water. I don't know what our pressure is coming into the house or the pressure of our unit.

The one thing that I learned about 10 years ago about the electric tankless units is that they weren't very efficient. But that was 10 years ago!

 

[Julian]

When you are comparing the use of 2 Electric 50 Gallon tanked heaters to one NG tankless, the savings are actually very good ($772/year) . Comparing Propane (our other choice) to Tankless Propane reduces this benefit to $415/year, and comparing NG of each drops it to $160/year. Our initial choice was to go from Electric to electric or Propane and tanked or tankless, so the cost comparison of installing the new propane based tankless compared to direct replacement of the electric tanked was:

Propane Tanks replacement $300x2= $600
Propane install - free
Install = $500
Total job $1100

Propane Tankless:
Propane install - free
Rennai tankless heater - $2200
Installation -$1000
Total Job $3200

So to recover the delta (3200-1100) $2100 would take (2100/415) 5 years. This of course uses Rennai's calculator which absolutely is higher than most savings on other sites like Energy Star. They claim an $80/year savings, which changes the ROI to 26 years!!!

Given my choice was to remove the Electic water heaters, I've definitely done much better than an $80 saving/year.....we estimate based on our bills we are around $20-30/month savings, or ~ $300/year. That gave us an ROI of 7 years (the tanked ROI would have been even better- like 2 years). So for us we saved no matter what....

 

[Bruce]

Have you considered a heat pump water heater?

I originally planned to install two electric tankless hot water heaters when I built my house.

I switched to a geothermal heat pump system which produces hot water as a waste product during the summer. We store 50 gallons of 100 degree hot water from the geo system in a turned off cheap 2" insulated hot water heater. Then we have a 50 gallon GE Geospring as our main hot water heater which adds the final 30 degrees before the water flows. The Geospring also acts as a dehumidifier for our basement. When we plan to have guests I turn on the second hot water heater. The Geospring is supposed to save $365 a year in electrical costs.

 

[txav8r]

Have you considered a heat pump water heater?

I originally planned to install two electric tankless hot water heaters when I built my house.

I switched to a geothermal heat pump system which produces hot water as a waste product during the summer. We store 50 gallons of 100 degree hot water from the geo system in a turned off cheap 2" insulated hot water heater. Then we have a 50 gallon GE Geospring as our main hot water heater which adds the final 30 degrees before the water flows. The Geospring also acts as a dehumidifier for our basement. When we plan to have guests I turn on the second hot water heater. The Geospring is supposed to save $365 a year in electrical costs.

Wouldn't you have to have Geothermal HVAC system in order to use a water heater like that Bruce?