Tankless water heaters-large capacity/least expensive?

[iibgdi]

I im looking for a tankless water heater that has large capacity for a house with the ability to serve anywhere from 5 to 10 people comfortably.

the square footage Of the home isn't particularly large but it has 5 bedrooms and will generally house anywhere from 5 to 10 people at a time.

Ideally I'm looking for the least expensive options out there .

 

[tomshep]

I've looked into this some. The units I was looking at were to support 3 bathrooms. The biggest issue was additional electric usage. It required 2 75W breakers or 4 40W breakers. Go into the project knowing you will have some wiring needed.

 

[Jmatlock88]

I have a Bosch 2700ES Natural Gas. It's plenty big for 3500sqft 3 bath house, but probably not big enough for you.

Here's what I want you to know about these heaters in general...
Anytime someone else in the house cracks a water faucet while you're in the shower, the temp will go cold, then overshoot too hot, then return back to normal. This happens over a 10 to 15 second period. It's the most annoying part of having this hot water heater.

If I lived with 5 people, I don't think I would use one. The temperature will always be disturbed and hunting for steady state.

The wait times to get hot water are a little longer too. This problem can be solved in various ways, by the way, but the solution will probably waste some energy.

Don't get me wrong....there are lots of things I love about my hot water heater. YMMV.

 

[ADSR]

Natural Gas or electric?

 

[Hmrhead]

Again, gas or electric? For that many people look at units with a high btu, high gpm out put, and a quick rise. Keep in mind that you are also limited by the gpm into the unit. Are you on city water or a well? Doubt that a single unit can provide enough hot water at temp you want for that much demand. You may need two units, but still depends on high gpm. Unless you are doing your own installation of the tankless units I would look at 2 50 gallon or a 50 and a 75 gallon conventional water heaters with quick recovery rates for your demand.

Also, if gas, you may need to up grade your gas meter in order to get enough gas supplied to run a pair of tankless units.

 

[volleyball]

You can cascade tankless so that they come on as need arises. It will have to be gas unless the OP has industrial power available.
Going to low flow shower heads will help.
There are other options but not knowing the weather where this is located, makes it not worth listing.

 

[Jmatlock88]

You can cascade tankless so that they come on as need arises.

My model and others specifically prohibit this arrangement. This would be a great way to increase capacity, he'll just have to review the datasheets to make sure this is allowed on the model(s) he chooses.

 

[mygarageone]

Tankless heaters go by the GPM it can heat at a given inlet temp .
They are not based on the number of people but again GPM. Gas or elec.
So you have to determine how many GPM you will be using at the highest usage.
In other wards will you have 2 showers going at once or a shower and a kit dishwasher , etc.
The best unit out there at a very reasonable price is Takagi , do an internet search on them and they'll have all the info you need to make a decision.
By the way stay away from the box store units , yes they are the brand name units but they are not the same as what's sold at a plumbing supply house.

This is a fact , if you properly size the unit and install it correctly , it WILL give you all the hot water you need.
The complaints you get about them that they run out of hot water , comes from improper sizing and install.
I have installed several of these units as far back as 10yrs ago and not one problem yet.
But then non of them are box store units.

 

[theoldwizard1]

Run the half-baths and kitchen off of an undersink unit. Don't worry about the dishwasher. It will heat its own water.

If you plan to be using more than two showers/tubs simultaneously, I would seriously consider a second unit in parallel.

 

[mygarageone]

My model and others specifically prohibit this arrangement. This would be a great way to increase capacity, he'll just have to review the datasheets to make sure this is allowed on the model(s) he chooses.

Takagi , has a whole design system for this type of application.
They show from 2 to 10 units in series.

 

[79firebird]

Cheapest way is get 1-2 tanks. as for that meany people a on demand is going to be like 3-5 grand

 

[mygarageone]

Run the half-baths and kitchen off of an undersink unit. Don't worry about the dishwasher. It will heat its own water.



If you plan to be using more than two showers/tubs simultaneously, I would seriously consider a second unit in parallel.

Note true , why do you think they have a hot water connection to them ?
The DW has to be taken into consideration !

 

[mygarageone]

Cheapest way is get 1-2 tanks. as for that meany people a on demand is going to be like 3-5 grand

You do not design the units by people but by GPM . It matters not how many people there are.

 

[mygarageone]

They make single units that can put out lots of hot water.
Please don't make a decision based on the number of people but on GPM usage.

A Takagi T-M50 will give you almost 9gpm at a70 degree. Rise. So if you water comming in is at let's say 35 degrees ,with a 70 degree temp rise that's. 105 degrees. Out at 8.7 GPM , drop the GPM to 5 and watch the outlet temp rise. A bunch.

Or install a storage type unit and run 9 GPM and you'll be out of hot water in 30 min.

 

[mygarageone]

The modern shower heads are aprox 2gpm and not all of that is hot but there is the cold water in that 2gpm .

 

[iibgdi]

Natural Gas or electric?

I would prefer gas. House currently has 100 amp service as furnace, dryer, stove, water heater are all gas.

I am likely going to upgrade the electrical service in a month or 2 to 200 amp.

So again, I'd say probably gas.

Also, I'm in the midwest if that matters. It's a rental house for college age kids. Mostly girls!


Maybe I'm asking too much to take try to keep up with the water demands of girls.

BTW, the tenants will be responsible for the utilities

 

[iibgdi]

Again, gas or electric? For that many people look at units with a high btu, high gpm out put, and a quick rise. Keep in mind that you are also limited by the gpm into the unit. Are you on city water or a well? Doubt that a single unit can provide enough hot water at temp you want for that much demand. You may need two units, but still depends on high gpm. Unless you are doing your own installation of the tankless units I would look at 2 50 gallon or a 50 and a 75 gallon conventional water heaters with quick recovery rates for your demand.

Also, if gas, you may need to up grade your gas meter in order to get enough gas supplied to run a pair of tankless units.

Thanks. Actually, at the inspection, the plumber suggested adding a water heater to the current one so we would have 2 conventional gas water heaters. The current one is pretty old and it's only 40 gallons

I was just wondering if the tank less option would be a better more economical option over time.

Again, it's a rental house and they are paying the utilities so maybe a conventional will be the best option for ME.

 

[iibgdi]

You can cascade tankless so that they come on as need arises. It will have to be gas unless the OP has industrial power available.
Going to low flow shower heads will help.
There are other options but not knowing the weather where this is located, makes it not worth listing.

located in the upper midwest. it gets cold!

I have order 1.75 gpm shower heads (for my house too) Niagra brand.

Gas.

 

[iibgdi]

Tankless heaters go by the GPM it can heat at a given inlet temp .
They are not based on the number of people but again GPM. Gas or elec.
So you have to determine how many GPM you will be using at the highest usage.
In other wards will you have 2 showers going at once or a shower and a kit dishwasher , etc.
The best unit out there at a very reasonable price is Takagi , do an internet search on them and they'll have all the info you need to make a decision.
By the way stay away from the box store units , yes they are the brand name units but they are not the same as what's sold at a plumbing supply house.

This is a fact , if you properly size the unit and install it correctly , it WILL give you all the hot water you need.
The complaints you get about them that they run out of hot water , comes from improper sizing and install.
I have installed several of these units as far back as 10yrs ago and not one problem yet.
But then non of them are box store units.

Awesome! I will start researching. Thank you!

 

[iibgdi]

Some complaints.

We do have hard water in the area. Sounds like it's an issue with them.

 

[iibgdi]

Info on sizing

http://www.takagi.com/?p=sizing.php&page_id=67

It appears to me that I would want the TM-32. Colder climate-3 showers

 

[iibgdi]

Some complaints.

We do have hard water in the area. Sounds like it's an issue with them.

I'm curious how big of a concern this really is. The city the rental house is in is known for having very hard water. This is a bit concerning for me.

 

[79firebird]

Could allways put a water softner in front of it. Looking at the price of that unit its about close to 3 grand. I my self would just get anouther reg tank as if that on demand fails you have no hot water. But if you get anouther tank and one fails you still do tell you can replace the outher one.

 

[yeldogt]

First - anyone thinking about a tankless should do some research before they install one - They are great for some applications not so great in other applications. They can be a problem for those on a well in a cold climate: Wintertime incoming water temps can be cold enough to drop the output of the unit enough to cause problems. High mineral content water can cause problems with maintenance on the units. Many people don't like the wait for hot water when one unit supplies the hot water to far flung bath/ kitchens.

I used them twice effectively: Both at shore houses that were built on slabs. We added a new kitchen and installed a unit just for the kitchen and another time we added a master bath and had a unit just for that. Both of these houses had the WH in the garage and the placement of the new additions made plumbing an issue... plus the rooms were far from the WH. Also, since it was a seasonal house not having more than one tank of standing hot water was positive. We still had to wait a bit for the water to get hot ... so if you pay a lot for water or have a marginal septic system -- this can be an issue.

I would never put on in a rental unit -- and even with 200 amp the big electric ones with make the lights flicker.

I'm just starting a complete rehab and replacing all the HVAC/ plumbing ... for me I'm going with a indirect.

 

[iibgdi]

Just talked to a contractor friend of mine. He said that if there is hard water, there is no way he would recommend tankless. In fact, he said the local guy that does them, will not even put them in in certain towns.

He recommended a 80 gallon conventional along side the current 40 gal and go from there.

Thanks all for the help.

 

[finn]

In addition to the hard water problem, I'm not sure where the savings would be in a rental situation. College students are going to be taking showers at all time of the day, and if you are in a cold climate, the heat loss of a tank isn.t truly wasted anyway, as it is going into the basement and floors.

It seems that tankless shines in low usage situations, like a home with one or two occupants that both work outside the home, a cabin, or spot usage.

 

[mygarageone]

In addition to the hard water problem, I'm not sure where the savings would be in a rental situation. College students are going to be taking showers at all time of the day, and if you are in a cold climate, the heat loss of a tank isn.t truly wasted anyway, as it is going into the basement and floors.

It seems that tankless shines in low usage situations, like a home with one or two occupants that both work outside the home, a cabin, or spot usage.

The new tank type water htrs are well insulated now days , most now use foam insulation.

 

[volleyball]

For a rental, in a hard water situation, I would think a quick recovery 80 gallon tank type would be the way to go if you don't have a boiler for heat.
They will adjust their water usage accordingly.
You can split the hot water piping and add a second if they take showers like those "movies"

 

[Charles (in GA)]

Spend the money on a Marathon tank type, you will never buy another one. All plastic with foam insulation.

Charles

 

[Highbeam]

Spend the money on a Marathon tank type, you will never buy another one. All plastic with foam insulation.

Charles

I see no real benefit to a tankless heater other than space savings and if you are on NG you can actually have cheaper operation.

A nice big marathon tank or tanks is a long term, low maintenance, lower cost, option. You want a dependable system for a situation like this.

 

[anthony666]

I see no real benefit to a tankless heater other than space savings

the benefit is you're not keeping 80 gallons of water at near boiling temperatures for long periods of time .. is it beneficial to let you car idle all the time so you can just jump in it and go ???

the trade off is minimum gpm to operate the system and the ensuing lag time

 

[Jackfre]

If you go tankless you will want one of the 180-199kbtu units. IN your area the 199, 95% units at a 70* temp increase will make 5.5 gpm...all day long. The 199 82% unit will make 4.8 gpm. If you pay attention to the shower heads you can run three showers simultaneously, again, all day long. My 2.5 gpm shower head will use 2.1 gal of 120* water mixing with .4 gpm of cold to reach my comfortable shower temp. A couple years ago we had 18 people in our house. We had only two showers but all 18 people got as long a shower as they wanted and there was no delay for recovery. I'm not sure how many showered together.

You can easily cascade multiple units as the manuf make the controls to do so. I have done a lot of those in commercial systems and in some residential applications. I once had a guy with a 25 gpm shower. It took five tankless water heaters.

The water should be tested and compared to the manuf specifications before using tankless.

 

[Highbeam]

the benefit is you're not keeping 80 gallons of water at near boiling temperatures for long periods of time .. is it beneficial to let you car idle all the time so you can just jump in it and go ???

That's just plain false. 120 degrees is what we set our water heaters for. Boiling is much higher dontchaknow?

Nothing wrong with keeping a reservoir of hot water ready to use. It is absolutely not the same as idling a car all the time. The stand by losses of a tank water heater are extremely small and insignificant. With 10 people in this home there won't be much "idling" anyway.

 

[mygarageone]

Tank verses tankless has been an on going argument for yrs . It's not about to change any time soon.
The newer tankless units in good water areas are pretty much trouble free , I have a few that are at the 10 yr mark and no issues yet. City water and Nat gas

 

[mygarageone]

That's just plain false. 120 degrees is what we set our water heaters for. Boiling is much higher dontchaknow?

Nothing wrong with keeping a reservoir of hot water ready to use. It is absolutely not the same as idling a car all the time. The stand by losses of a tank water heater are extremely small and insignificant. With 10 people in this home there won't be much "idling" anyway.

True and anymore I refuse to set the water htr temp higher than 120 do to law suits should someone scald them selves.
Fact is the inspectors actually take temps from the hot water faucets and it higher than 120 , we hear about it .

 

[Charles (in GA)]

The Marathon heater will go somewhere around 24 hrs without cycling on if you don't draw any water from it. Being all plastic, there are no corrosion problems.

Charles

 

[2Big2Ride]

Originally wanted an electric tankless water heater in the shop - going to have a full bath and a kitchen style sink if I ever get off my **** and finish the thing - after researching what happens with slightly hard water conditions, needed maintenance for electric tankless, and heavy power supply requirements I have changed my mind. Plan on going with a small Marathon now.

 

[anthony666]

True and anymore I refuse to set the water htr temp higher than 120 do to law suits should someone scald them selves.
Fact is the inspectors actually take temps from the hot water faucets and it higher than 120 , we hear about it .

code here is 160 in the tank to kill ecoli, mixed down 118 delivery

 

[BadgerBoilerMN]

Your local plumber should be able to help you. We specialize in high efficiency domestic hot water heaters and boilers including Bosch, Rennai, Tekagi and Eternal.

If the tenant if paying the fuel bill this is clearly a case for a tank-type water heater; two 40's should do nicely, but make them 50's if you don't mind the up-charge.

 

[Jackfre]

I have a Bosch 2700ES Natural Gas. It's plenty big for 3500sqft 3 bath house, but probably not big enough for you.

Here's what I want you to know about these heaters in general...
Anytime someone else in the house cracks a water faucet while you're in the shower, the temp will go cold, then overshoot too hot, then return back to normal. This happens over a 10 to 15 second period. It's the most annoying part of having this hot water heater.

If I lived with 5 people, I don't think I would use one. The temperature will always be disturbed and hunting for steady state.

The wait times to get hot water are a little longer too. This problem can be solved in various ways, by the way, but the solution will probably waste some energy.

Don't get me wrong....there are lots of things I love about my hot water heater. YMMV.

You have the problems you describe because you have the Bosch. In my experienced opinion the only good Bosch unit they have is the one Noritz let's them private label.