Tankless water heaters

[ERD50]

I'm not sure I really understand that assumption (of not needing to heat the cold output). These systems always use indoor air (and don't draw from outside), right? So, in the winter, clearly, you will have to somehow heat the air that then gets used by the water heater heat pump. Or are we assuming that there is actually an added benefit in the Summer in that the system actually provides extra air conditioning. And somehow the winter/Summer situations are a wash?

As JoeWras replied, it's totally dependent on your particular situation. *if* you have to heat that output, it's a hit on the payback. It *might* get offset by cooling season. It just depends on lots of things, your climate, and where the 'cold' is being dumped.

-ERD50

 

[rodi]

A possible concern

We’re told - that the water here is hard, and a tankless needs to have a water softener.

Don’t know the veracity. Have not checked options, yet - and whether water is so hard that needs softener regardless

We have very hard water. The maintenance on our tankless is that once a year we need to flush it with vinegar. It's a pretty easy process. We have to do the same on our coffee maker. Lol

 

[rodi]

One of the driving factors for me was the possibility of moving the water heater from one side of the house to the other. The previous location was dictated by the flue, which was far from the runs to hot water usage. I moved the tankless heater to the other side of the house, which is right near the hot water outlets.

This was our driver for moving to tankless. Our tanked water heater was in the garage and the uninsulated hot water pipes went into the cold concrete slab, then up through the walls to the attic, dropping down to hit both upstairs bathrooms, then the downstairs powder, and finally the kitchen sink. It took 5 minutes to get hot water to the kitchen sink. Not exaggerating.

Now our tankless is on the outside of the kitchen wall, and does shorter runs, not through the slab. I can get hot water in the upstairs baths in less than 30 seconds.

Saves water... bonus.

 

[bobandsherry]

We have very hard water. The maintenance on our tankless is that once a year we need to flush it with vinegar. It's a pretty easy process. We have to do the same on our coffee maker. Lol

For those curious, here's video on how to flush the tankless. Not quite as simple as coffee maker, or even a regular water heater.

https://youtu.be/M3WzxW0hv9s?si=mwgOr5JyswbnnnxB

 

[Music Lover]

We have very hard water. The maintenance on our tankless is that once a year we need to flush it with vinegar. It's a pretty easy process. We have to do the same on our coffee maker. Lol

Most people don't drain their regular HW tanks, I doubt they will suddenly step up for a tankless.

IMO, with tankless you get the same hot water but it costs more and requires more maintenance.

Of all the places to save money, tankless is very low on my list.

 

[ShokWaveRider]

IMO, with tankless you get the same hot water but it costs more and requires more maintenance.

Of all the places to save money, tankless is very low on my list.

What Total Rubbish!

We moved to a Tankless Gas Water heater from as Gas Tank heater 12 Years ago, it is still running and has paid for itself as least thrice.

Typical uninformed or misinformed statement. That is the problem, people believe anything these days.

Now electric, would probably be a different story.

 

[bobandsherry]

I understand your other points, I was just pointing them out for the general case.



And the "may" offset is the question (and I don't know the answer).



-ERD50

FWIW, I asked Chat GPT and got this answer...

One source estimates that hybrid water heaters can reduce CO2 emissions by 62% compared to traditional tanked water heaters3.*Another source claims that hybrid water heaters can save up to 3,000 pounds of CO2 per year compared to electric heaters and 1,200 pounds of CO2 per year compared to gas heaters4.

Over a lifetime of 10 to 15 years, this can amount to a significant reduction in the carbon footprint of a household.

In addition to reducing greenhouse gas emissions, hybrid water heaters may also have other environmental benefits, such as:

Reducing water waste, as they provide hot water on demand and do not require long waits for the water to heat up2.

Reducing landfill waste, as they have a longer lifespan and require less maintenance than traditional water heaters2.

Therefore, hybrid water heaters can offer many environmental benefits over their lifetime, making them a more sustainable and eco-friendly option for water heating.

 

[Music Lover]

What Total Rubbish!

We moved to a Tankless Gas Water heater from as Gas Tank heater 12 Years ago, it is still running and has paid for itself as least thrice.

Typical uninformed or misinformed statement. That is the problem, people believe anything these days.

Now electric, would probably be a different story.

Not rubbish. My parents have a regular gas HW tank. In summer when it's the only appliance using gas they use less than $20 a month to both heat and store hot water. Those are real numbers, I've seen their utility bills.

I don't know what a tankless would cost, but at $20 for a regular tank I can't see it paying itself back even once, never mind 3 times over.

 

[ERD50]

Not rubbish. My parents have a regular gas HW tank. In summer when it's the only appliance using gas they use less than $20 a month to both heat and store hot water. Those are real numbers, I've seen their utility bills.

I don't know what a tankless would cost, but at $20 for a regular tank I can't see it paying itself back even once, never mind 3 times over.

And that $20 would usually include some fixed fees.

Our summer bill is $33, including gas stove. Most of that is a fixed $22.14 charge. Just $6,.56 for the gas, plus taxes, etc, but be generous and say $33.23-$22.14 = $11.09/month to heat water (and gas stove/oven). A quick search on Home Depot shows popular gas tankless about $900 more than tank. So ~ 6~7 year payback, and 9 years adding 4% lost opportunity cost.

Not bad, but nothing too exciting, unless there are other factors involved as some have mentioned (like moving the water heater closer to where water is used).

I like simple, so when our water heater died, I just replaced it with another tank unit.

-ERD50

 

[JackJester]

Wow. Surprised how emotional this topic is. Everyone's case is different based on where they live, cost of electricity, concern about the environment, etc. We have Tankless (a.k.a., "On Demand") powered from propane here in our house in the WA Cascade foothills. I would NEVER go back to a tank water heater. The negative environmental impacts of a tank are well documented, which is important to us. But I also prefer the reduced space footprint in our utility room and the lack of concern of a tank blow out. We also have a condo up in BC Canada and there have been soo many problems of tanks going bad and causing flood damage that residents are now required to replace their tanks every 10 years. Unfortunately we can't go tankless in the BC condo. I am going 15 years no problem on the tankless at the WA home. And if we have guests, there is never a case of 'not enough hot water'.... nothing worse than taking a cold shower.

 

[COcheesehead]

Most people don't drain their regular HW tanks, I doubt they will suddenly step up for a tankless.

IMO, with tankless you get the same hot water but it costs more and requires more maintenance.

Of all the places to save money, tankless is very low on my list.

The Rinnai tankless we have will give you a service code when you need to flush. Flushing also maintains our warranty so its worth the $90/ a year plus the energy savings.

 

[SecondAttempt]

You are receiving completely incorrect information. Most 30, 40, or 50 gallon electric water heaters require (1) 30amp dual pole circuit breaker. No residential water heaters require (2) breakers - ever (unless you actually have 2 different physical water heaters in a very large home). The size of the breaker and the size of the electrical wire are determined by the watts drawn by the heater elements. The size of the tank is irrelevant in determining breaker and wire size. 100amp rated panels are completely fine for feeding water heaters up to 50 gallons. 99% of the heaters I've installed or seen, operate on 30amp breakers and 10-2 Romex wiring. Consider the information in the following for detailed explanations or PM me. Happy to help you make sense of this:

I'm interested in hearing more. The small water heater I'd be looking at says it requires two 40 amp double pole breakers. I'm an engineer but not electrical. To me that means it might draw 80 amps from the main. Maybe it's 40 amps per phase with the main at 100 amps per phase. Is that what you are getting at?

 

[JoeWras]

Wow. Surprised how emotional this topic is. Everyone's case is different based on where they live, cost of electricity, concern about the environment, etc.

It's interesting, isn't it?

I wish people would just live and let live. I see advantages and disadvantages to the many different types of systems. Just let me choose.

You mentioned one of the items that causes emotion. Judging by how it went with EVs, we can expect some serious emotions building up regarding appliances as time goes on.

 

[ncbill]

And that $20 would usually include some fixed fees.

Our summer bill is $33, including gas stove. Most of that is a fixed $22.14 charge. Just $6,.56 for the gas, plus taxes, etc, but be generous and say $33.23-$22.14 = $11.09/month to heat water (and gas stove/oven). A quick search on Home Depot shows popular gas tankless about $900 more than tank. So ~ 6~7 year payback, and 9 years adding 4% lost opportunity cost.

Not bad, but nothing too exciting, unless there are other factors involved as some have mentioned (like moving the water heater closer to where water is used).

I like simple, so when our water heater died, I just replaced it with another tank unit.

-ERD50

Same $6-$7/month here just to heat water.

But that's natural gas.

Some places propane could be so expensive the tankless beats tank on operating cost with propane instead of natural gas.

But tankless remains significantly more expensive to purchase & maintain, at least when you don't DIY.

 

[Affinity4Investing]

I'm interested in hearing more. The small water heater I'd be looking at says it requires two 40 amp double pole breakers. I'm an engineer but not electrical. To me that means it might draw 80 amps from the main. Maybe it's 40 amps per phase with the main at 100 amps per phase. Is that what you are getting at?

Exactly what make/model are you looking at? You must be speaking of a "tankless" model or a tank model in the 80gal range that pulls some serious wattage for the heating elements? I have been speaking to you WRT electric water heaters only - nothing gas related and nothing "tankless".

Whatever you are talking about will not draw 80A from (2) 40a DP breakers. If it did, you would constantly trip the breakers. By NEC code, breakers for specific needs are 'oversized' so as to provide the required max load but also provide some overhead to mitigate breaker tripping and circuit overheating. By code, breakers must be sized at ~125% of the intended max load. So that is to say, at full load on the circuit, the breaker will handle ~25% more electrical load than the water heater requires. So if you are being told you need (2) 40a DP breakers, at max load, the heater will pull ~60a. Codes vary - but this is the general rule.

If you are maxed ~ 100a on your panel, I'd discourage you from installing this device into your mix. Remember, your panel @100a is also intended to provide that same ~25% overhead window - meaning that you really should have no more than ~75a total in-use in your home at any one time. If you drop this 60a max load device into your house, that gives you ~15a for everything else. That's not gonna happen and in actuality, invites IMO, an electrical fire at some point.

All of the info posted is based on my experience & understanding of the NEC circa 2008 - with some changes thru the latest edition. I have read/studied the majority of the ~3" binder. I also spent most of my life in a small town with homes ~ 70-150yrs old where multiple homes burned every Winter because of overloading their 100a (and smaller) panels. Hope this helps.

 

[MichaelB]

<mod note> A reminder that we can disagree without being disagreeable. Let’s please keep a civil and respectful tone.

 

[Breedlove]

We have a tankless water heater , about the size of a thick phone book . We have a 60 amp double pole breaker . Never have we had a problem , of course it is on a separate circuit. Hot tub has a 40 amp double pole breaker .

 

[Breedlove]

I looked on Amazon at my Ruud water heater . All it requires is one 50 Amp breaker . You can do two showers and wash dishes at the same time 248.00. It was real simple to install.

 

[meleana]

We have one and we live in New Hampshire and the only issue we have with it is in colder months it takes longer for the hot water to come out of the hot water faucet so you end up wasting more water waiting for it to get hot.

The rest of the year it’s great.

 

[ShokWaveRider]

We have one and we live in New Hampshire and the only issue we have with it is in colder months it takes longer for the hot water to come out of the hot water faucet so you end up wasting more water waiting for it to get hot.

The rest of the year it’s great.

Recirc pump fixes that. Just put it at the end of the run. We have used one for the last 10 years. It is on demand not on all the time.

https://chilipeppersales.com/

 

[scrinch]

Since there's no hot water tank on a tankless WH, where is the hot water coming from for the recirculation pump? Is the tankless WH constantly on at a low level to feed the recirculation pump?

 

[Koolau]

It's interesting, isn't it?

I wish people would just live and let live. I see advantages and disadvantages to the many different types of systems. Just let me choose.

You mentioned one of the items that causes emotion. Judging by how it went with EVs, we can expect some serious emotions building up regarding appliances as time goes on.

Yeah, when I see pounds of CO2 thrown into the argument, it tends to get even more emotional. I try to limit my affect on the planet, but I don't typically count pounds of CO2. If I did, I'd never fly again. I just flew home from the frozen tundra of the mid west. I was "credited" with over a ton of CO2 for my 9 hours in the air. Now, that's still Prius type "gas mileage" per seat, so not that bad, but jeepers! Over a ton in 9 hours. That compares to hot water for a year, so again, I just can't get too excited about all the CO2 we're generating - or not generating. Our overall (USA wide) energy efficiency has dramatically improved over the past 30 years. I'm good with that and have tried to do my "share" - whatever that is. In any case, YMMV.

 

[68bucks]

We're on a well so no power, no water. No earthquakes worries here. My pressure tank will deliver a few gallons of water without power. He have a standby generator so not concerned about supply. At least until the propane runs out. We will go tankless when we replace the old one soon.

 

[Music Lover]

Yeah, when I see pounds of CO2 thrown into the argument, it tends to get even more emotional. I try to limit my affect on the planet, but I don't typically count pounds of CO2. If I did, I'd never fly again. I just flew home from the frozen tundra of the mid west. I was "credited" with over a ton of CO2 for my 9 hours in the air. Now, that's still Prius type "gas mileage" per seat, so not that bad, but jeepers! Over a ton in 9 hours. That compares to hot water for a year, so again, I just can't get too excited about all the CO2 we're generating - or not generating. Our overall (USA wide) energy efficiency has dramatically improved over the past 30 years. I'm good with that and have tried to do my "share" - whatever that is. In any case, YMMV.

I'll start caring about CO2 when the climate "experts" take it seriously enough to have their annual meeting with a Zoom call instead of flying to an exotic location with 200 private jets.

 

[bl1289]

make sure to follow all install rules

I looked into this some years back to replace a gas tank hot water system for a 3 bedroom home. I much liked the idea of freeing up space in the garage as my cars are big and space is tight.


what I found is that to install a unit big enough for a 3 bedroom home would need a bigger gas service, a bigger exhaust gas flu, and other substantial changes. I was told that many people either buy too-small units so they don't have to get a bigger gas line, or they get the bigger unit but don't resize the gas line, and neither of these work out well.


Also the size you need varies a lot by the temp of the intake water. In a northern state with colder ground water you need a significantly bigger unit for a 3 bedroom home.