We are in the process of designing a new home +/- 3,000 sf. It will run on propane.

Is there a significant advantage to going tankless? Is there a large cost difference?

I know they heat "on demand" but what about the water that is in the pipes? Does it constantly circulate water?


Are there certain go to brands? brands to stay away from?

any other pertinent information?

Moved into a new build with one about a year ago.

My understanding is the biggest advantage is cost of ownership.

I don't know the exact breakdown in terms of energy cost but I've been told the gas cost vs electric cost is about a 30% per unit of heated water, plus then you save a couple grand every 7-8 year on not having to replacing a water heater. So you get heated water for 70% less w/ no long term replacement.

It does not circulate water, you have to let the water run till the hot water gets there. So just like a regular water heater, the further from the source to longer. (which with the way my house is designed is a pain, the master shower and kitchen take forever to get there, but the bathroom closest it's almost right away)

You never run out of hot water, So when you have company, everyone can take long showers at the same time and everyone is happy.

My issue is that I wish I could turn the heat up a tad on mine and it's already set to the highest it will allow. It's just a hair not hot enough for me.

No clue on brands or options because I didn't get to pick that. ( Maybe one that let's you set it a couple degree's above the safety max setting)

You can have a recirculating pump installed for more instantaneous hot water. Some units have a pump built in. Navien is the manufacturer I like best (have owned same unit for 13 years) but Rinnai is another brand I have owned and liked.

Maintenance is relatively easy. No electrodes to corrode/burn out. No tank full of sediment to dispose of when the unit dies. Takes up less space. High efficiency units can be exhaust piped with pvc.

Only uncommon variable I see here is a departure from the typical gas vs. electric argument. NG vs. electric is a no-brainer. Propane is expensive. But, electric tankless sucks bad...

P.H. Dexippus said:

---

Maintenance is relatively easy. No electrodes to corrode/burn out. No tank full of sediment to dispose of when the unit dies. Takes up less space.

---

this can't be stated enough. Maintenance is super easy and don't have to worry about to bottom rusting out...especially if you have a water heater up in the attic!

I switched to a Rinnai tankless probably 7-8 years ago and it's been great!

I'm interested in how much propane the tankless would use vs the traditional.

How much would it use with a recirculation pump?

Navien is awesome because you can program when you want recirculation (i.e morning and evening high use times) and both heat exchangers are stainless steel. Others have 1 copper one, which I didn't want to worry about corrosion.

This is good information. Thanks

Leggo My Elko said:

---

You never run out of hot water, So when you have company, everyone can take long showers at the same time and everyone is happy.

My issue is that I wish I could turn the heat up a tad on mine and it's already set to the highest it will allow. It's just a hair not hot enough for me.

No clue on brands or options because I didn't get to pick that. ( Maybe one that let's you set it a couple degree's above the safety max setting)

---

I had the same issue with my Rheem, and there was a hidden setting that let's you go higher. It wasn't a safety issue - just has to do with how many GPM it can deliver at that higher setpoint. You might Google your model and see if there's a way you can increase it. I think the sequence was called in my manual, just not obvious on the control panel.

The higher the temp setting, though, the less on-demand water you can expect. I do struggle if we run three showers simultaneously. It works, but definitely a reduction in flow-rate. We still have our high-flow 90's fixtures in a couple of bathrooms, so replacing them might help in my case. But with 5 kids in our house, the ability to take shower after shower is very nice and a definite upgrade from our tanked units.

Check my math but pretty sure at $3/gallon for propane vs 15 cents per kWh it's a break even between electric vs propane (propane is pricey). Gallon of propane is 91k btu. 91k btu is 26.7 kwh electric which is about $3.20 electric. Your gas heater will be between 80-95% efficient vs 99% for electric so it's a wash. Unlimited hot water is great - without a circulator or a tank your pipes can get real cold depending on where you live (freeze issues) that a tank might mitigate due to the heat bleed into the pipes (if it's in garage or attic)

The design for new housing SOP, even the tract/spec:

Gas/propane (electric so buggy/etc/etc, some subs will not install them)
Hanging at least two on exterior walls (these do come in Sizes)
Locations as close to the important no-waiting fixtures (CODE limitations are not abusive)
(Yes recirculating pump options galore)
Brand: whatever the locals will service pronto (Consumer Reports has a blind eye to all but Heat Pump types .. UGH)

The only caveat mentioned in past was the Texas Feb'21 super freeze when some bragged about their tank water heaters spoiling them ... even the electricity came on-off enough with some problems reported with the exterior demand ones w/o internal heaters.

I have a Rinnai 98 (I think that's the model). I have it turned up to 140*, which is plenty hot. The whole house is gas, and that bill runs about $20 in the summer and about $100 in the winter. 2 adults and 1 older teen that likes looooong showers. I will never go back to a tank, or electric water heater.


ETA: the unit is in the garage. During snowvid, I just put a small space heater under it and didn't have an issue.

Whatever you do, don't buy a Rheem. They're not very reliable, and it seems like nobody really knows how to work on them.

I was having my hot water heater (tanked) serviced last week. It is 4 years old and had it flushed for the first time. It had been acting up with inconsistent temperatures.

The tech suggested replacing it with a Navian tankless, so I told him to give me a quote. His quote was $12K! I was expecting $4-$7K. If I decide to do it, I'll get better bids. It is currently located in the attic with lots of room to work.

If you have gas plumbing already in place and are decently handy with plumbing, you could DIY a high efficiency Navien install and save yourself about 10g.

Depending on the bathroom setup and design of the house, you might consider two units. Our last house was about 2700 sq ft with one tankless on one end. The bathrooms on the far end took a bit to warm up. Our current house has one on each end. It makes a lot of difference.

I have the Navien 199kbtu.
Got it for about $1300 and got family/friend pricing for labor since I work for a GC. $10k does not seam unreasonable considering my plumber took a good 40 hours

But this is not a DIY job unless you have done a lot of plumbing, also assuming when you remove the tank, you have a lot of rerouting to do (or is this a new build?)

I made a huge mistake and didn't get the one with a recirc pump. Since my house didn't already have one, there was no way to tie in a hot line from upstairs for it to work. Then after install, we found out it took a full 100 seconds to get hot water to kitchen sink. This was not acceptable. Luckily we hadn't finished basement yet (where water heater is), so I then bought a $500 recirc pump to just recirc the kitchen line. Instant hot water.
Sucks cause the tankless with the pump was only like $200 more.

I redid all the plumbing when I purchased and remodeled my house in 2008. I had the gas line run and new plumbing done to use a tankless unit in the attic. This was ideal timing since you need a larger gas line than tank heaters. So it did not add cost to what I needed doing anyway.

The Japanese brands seem to be the most reliable (no surprise) and I bought the Takagi TK-3 then. I replaced it a few years ago with their updated model. I do not have recirculation.

We've been very happy with this direction.

For power outages: Since the unit only need electricity for the ignition and controls, it doesn't use much. I hate cold showers, so I've tried keeping it plugged into a backup power source like used for computers. It works for awhile. If the electricity is out, there is enough power to start/run the heater while the natural gas provides all the heat.

But It seems these UPC units just don't last very long in a hot attic, maybe a year.

mefoghorn said:

---

This was ideal timing since you need a larger gas line than tank heaters. So it did not add cost to what I needed doing anyway.

---

I'd assume this is typical, but while my tank wh only had a 1/2" line, it was just literally about 2 feet up the line that it was reduced to that 1/2" down from 1".. since it was feeding furnace and stove from that point. and it was far from there it was reduced from 1.25" down to 1".

The navien called for 3/4", so where it reduced from 1 to 1/2, that fitting was simply changed. I would guess the reduction of the water heater line isn't very far away from the tank in most houses.

I wanted it all rerouted anyway to open up the space completely where the old tank was, now I have a 5' work bench and tankless on the wall to the left.



I upsized my vent in case I ever want to put another tankless in for whatever reason. two in tandem requires the 3" whereas a solo only requires 2".. Something to think about.

Spring TX. I just got a quote for a Rinnai tankless system for $6,800. You should look around to other shops.