We have the same size house as yours. 4500 sq/ft cape. Only 3 1/2 baths and no basement. 3 of us. The master bath has a shower set-up with multiple heads, sprays, etc and a large air bath. We decided to use a dedicated tankless just for our bath...we went with the largest capacity Rinnai (LP, exterior mounted on the wall outside of the bath)available. The rest of the house is serviced by a 75-80 gallon Marathon hot water heater. We have had no problems with running out of hot water.

If you go with a tank system, why not use 1- 100 gallon? It takes up less space than 2-75 gallons, but will enable you to have more as a backup? I'm not sure of the energy efficiency of keeping the water hot for the different sizes. You'd have to look at the specs. Definitely check out the Marathon units (purchased or made by Rheem now), they are vastly more energy efficient than most of the junk sold out there.

In our current home, we have a bit of a different scenario. It's just DH and me, and our home is large (6500'). We have 2 full baths with double sinks, large walk-in shower and separate tub in each, and 2 half baths. Kids and grandkids come twice a year for 2-wk visits. During that time there are 11 of us. We have one 75/gal gas hot water heater, and we've never run out of hot water. Lots and lots of showers, dishes, and laundry being done.

In a previous custom home we built, we put in a tankless hot water heater, and I really disliked it. To get really hot water, the water flow was reduced to a trickle. I'm sure they've improved since then, but I'd really check them out. After a few months of use, we ended up taking it out and putting in a regular gas water heater.

You might consider these newer ao smith vertex units units.

http://www.hotwater.com/products/residential/rg-vertex.html

They are tank type, high efficiency, claim to be virtually continuos. The cost is surely higher not unlike tankless. Some have complained about cold spots and other issues when turning on and off a faucet with tankless. I believe they are best for elderly or empty nesters who use less water or are not home as often than large families personally. Then you may want to run a circulation pump on the hot water line to preserve constant hot water in line and not have long waits. Good Luck

We get plenty of hot water, but if I had to do it all over again I would not go with the tankless hot water heaters. We have two bosch units (that are super efficient) that run in tandem for our shower that puts out 12.5 gal/minute.

First of all, it seems to take forever to get hot water (1min in kitchen, 2+ upstairs). I think a large part of the issue relates to the units having to turn on, get going and then send the hot water down the pipe.

The next best option (as i understand it) for energy efficiency would be to do an indirect tank off your boiler, if you are going the hydronic radiant heat route. You can get a 100 gal tank that is very efficient, so long as the boiler, etc. is sized appropriately.

Just my .02- good luck.

As Mdev said the problem with tankless on larger homes is they have long runs often times to get to your location of use. Its difficult to add a circulation pump on these hot water lines because they only run on demand. This causes long delays to anywhere you might be a distance from the WH. Thats why I see them best used for smaller homes tight on space with shorter runs, apartments, condos and empty nesters who may travel or take few showers and wash clothes less often etc. You will love the circulation pump on hot water line for almost instant hot water and it uses very low wattage to run. You also dont pay for running well pump or for water /sewer charges for all the cold water that is run down the drain waiting for hot water.

pps

The most important decision is the location of the hot water source (whatever it is) with respect to the point of use. if you put a tank (or tankless) source far away from the point of use, it will take a long time to get hot water at the source. Look up how much water is stored in a 10 foot length of 3/4 inch or 1 inch pipe which is the typical diameter for the main feeds in the house. My house is over 100 feet long and it turned out to be over 7 gallons of water. When you turn on the hot water at the kitchen sink - that 7 gallons has to be pushed out of the way - and it can take up to 5 minutes depending on the fixture.

I would put a hot water source as close to the master suite as you can get it. I use tankless (but tank would have worked too) and we put the units right under master suite which is on the first floor above. It takes seconds to get hot water - which is nice!

If you are putting a hot water source in the basement and master suite is on second floor - then you might want to plan for a recircultating pump which can be put on a timer. This pump will turn on at pre-selected time and keep hot water in the line so that you don't have to wait forever to get hot water. All that is needed is for a second 1/2 inch return line to be run along side the hot water feeder line running to the second floor. The pump circulates the hot water from the tank through the feeder line and back through the return line to the tank to keep hot water in the loop ready for use. The pumps are low power and and be programmed for time of day.

Focus on the hot water distribution design first (the plumbing) then make the selection of the power plant. I would also insist that all hot water pipes (or at least the main feeder lines) in the house were wrapped with foam insulation since it will keep the water hot after it is turned off - at least for a while.

I have gas powered tankless and like them but they aren't for everybody. Most of the complaints about the long wait times have more to do with a poor plumbing design and not the very short delay for the tankless units to cook the water to the set temp (about 5 to 10 seconds).

I will say that the nice thig about tankless is if you have a bubble tub - you won't run out of hot water after you fill it up. The main reason we went with tankless is that it is just me and DW in a large house with occasional guests. When guests are here we need a lot of hot water. When they aren't here - not so much unless we fil up the bubble tub. So it works nice for us but it does take some getting use to.

We have 2, a 50 upstairs and an 80 on the lower level.

I know it is tied into the geothermal somehow, but I haven't really asked too many questions about the how's & why's to all that yet, but this reminds me that I need to.

I love my long hot baths and don't want to run out. The new steamshower tub has some sort of heat pump thing in it also to keep the water warm, but still we thought we just as well go ahead with the second one.

The old house, it took forever for the hot water to get up to the top floor, but once it did, we always had plenty. So we thought about just going one tank with the pump, but went ahead with two. I am not sure how the cost would have compared. I guess long run, with a pump you wouldnt have to heat two tanks when not in high demand.

And I say it took forever, it really didnt take very long, just seemed like it sometimes :-)

I have to agree with sniffdog. Our 2 story house is also over 100 feet long and we have 2 tankless heaters, one on either side of exterior of the house. One of the heaters is close to two bathrooms and powder room, the other is next to the kitchen, laundry and two bathrooms. We have almost instant, and endless hot water in all locations.

For us the best things about tankless, apart from not heating water unnecessarily, is not having to use up valuable space for tanks and not having additional heat sources in the home (we live in a warm/hot climate). We also have a lot of guests so the flexibility of the tankless supply really works for us.

We are going with two tank units in the basement of a approx 4000 ft2 house with 6 people. The two units are due to using a geothermal heat system. They recommend that you have one tank to take in the wasted heated water and store it, when you use hot water, the main hot water heater sends the water, and the second one refills the original one with preheated water. Less heat is needed to get the water to the right temperature and the heat for the 2nd take is a byproduct of the heat system. The placement in the basement is very customary here, but to eliminate the problem of waiting for water on the 2nd floor we'll run a continuous loop system.

We'll have 2 washer/dryers (but we almost exclusively use cold water for washing clothes), 3 showers, dishwasher etc...

Will a gas fired tankless hot water heater work when the power is out?

You haven't mentioned what you will have for bathroom fixtures, which is vital information when determining potential water usage. Will you have a Jacuzzi-type tub? Will you have shower body sprays? Body sprays use a LOT of water. We have a 75 (I think) gallon Super-stor (technically not a hot water heater, stores water heated by the boiler) and we never run out of water (it's just the two of us). However, I do wish I had used a tankless just for the master due to the distance issue (mine doesn't take 5 minutes, more like 1 minute, which is fine when showering but a PITA when you just want to wash your hands).

If distance isn't an issue for you, I would do the one tank but allow space for adding an additional one. Unless you have high water usage fixtures you won't need two tanks because of your family size. However, for resale purposes (how long will you be in this house? Past the life of the hot water heater?) you might want two due to the number of bathrooms.

It's just the two of us, but we get a housefull occasionally and my 50 gal gas WH has never disappointed. I designed the house to have the WH centrally located...distance in feet to these locations: Sink in powder 4', kitchen sink and dishwasher 6', washer/master sink/master shower 20'. Upstairs bathrooms are somewhat longer runs, but they're not used very often.It's a real pleasure and certainly less wasteful to have quick hot water.

Hi,

Just to chime in, I did build a house and we have a 80 gallon oil fired hot water for heating and hot water.

I'm in New York. If I had to do it again with these high fuel costs I would give serious consideration to solar hot water. The units I would consider are the glass tube units. They come in a panel of maybe 30 glass tubes. Each tube is 5 feet long and about 3 inches in diameter. Inside the double insulated vacum is a copper tube. These systems claim that they will heat hot water down to freezing temps. They work on light and radiated heat. The system is also frost proof (not sure where you are), because the circulation has an anti-freeze type mixture. There are a number of manufacturers, just google for Evacuated-tube solar collectors. The link is from the US goverment Dept. Energy. There is some info there.

The other thing which may interest you is CHP, Combined heat and power from Honda. Yes the same company that makes cars and mowers. If you have propane or natural gas you can use this thing. In a nushell the unit is a small propane engine. The hot water comes from the radiator side. The motive power is used to generate electricity. So if you have Net metering you can sell power back to the grid and lower your power bills. The idea is that for every unit of gas (propane / natural) you burn you use more of the energy. The technology has been used extensively in Japan where electrical power and heating costs have been substantially higher than the U.S. Check out the "FreeWatt" site, or the Honda USA site.

Warmest regards, Mike.

Here is a link that might be useful: US Dept Energy link

ncamy

the gas fired tankless units I have looked at (and the ones I have - Rinnai's) will not work unless they have electricity to operate the digital controllers and the electric igniter. But the amount of electricity required is very small - probably less than a few amps.

I put the outlets that my Rinnai's plug into, as well as my well pump, on my backup generator so that when power is out, i have both hot & cold water.

If you do decide to go with tankless - only consider gas units. The electric whole house tankless units require a lot of current - far in excess of what your typical household backup generator can supply.

On the flip side, tanked systems are much easier to implement a recirculating system. With a tank - all you need is a small pump and the return loop line. With a tankless system, you have to add a small holding tank on the output side of the tankless - and that holding tank will most likey be a small electric tank (mine is a 4 gallon tank). If you don't put that holding tank in, then your tankless units will fire whenever the loop pump is running (could be for hours) since they use water flow to detect when to turn on. And if that happens, you will hate your gas bill.

You can also look at a hybrid system. As an example: if your second floor suite is mostly for occasional guests - use tankless for that suite so that you don't have to continuously cook water with a tank. You could then use a tank for the master suite. You could also look at point of use hot water tanks which could service a kitchen or bathroom sink. Point of use units require an electrical outlet (most require a dedicated circuit) to be installed below the sink. As long as you plan for it ahead of time - this isn't an issue. But adding these outlets after the house is done can be a challenge..

There are many possibilities for the hot water power plant - all of them have strengths and weaknesses. But none of them can overcome a poor plumbing design. You have to look at your house design and determine the best way to plumb it for the hot water - always keeping in mind that the longer the length of the main feeder lines to the source, the longer the delay for the hot water. It is also very hard to get a perfect system because of the way houses are typically layed out and constraints for running the pipes.

Unfortunately, the hot water plumbing design is generally an afterthought. During our build, we did think about placement of the tankless under the master suite but never realized that this selection would cause such long delays in the kitchen which is over 100 feet away. Thankfully we were able to fix this issue witha recirculating system but it isn't an optimal solution. Hopefully you can avoid these pitfalls.

We did two tankless Rheems, 5.3 max gpm each, in our 5,500 sq ft home. We can run two showers at a time before our well gpm hits its max. I wouldn't get Rheem, one broke a month in and it was a fiasco getting it replaced under warranty.

Tank vs Tankless, we chose tankless because we're a big house with few people until family and friends arrive. So we aren't wasting energy while no one is visiting.

Either way, put in a recirculating pump, big houses have long pipe runs. It can take minutes to get hot water at some or our taps.

Thank you everyone for the great advice! My builder has also mentioned long runs to the kitchen and my son's bath. Since we have a wide and shallow house it seems the best thing to do is to put two water heaters at different ends of the house with shorter runs. I think I will put a 50 gallon tank that feeds my son's bathroom, kitchen, powder room and a larger 100 gallon tank to feed the master, washing machine and guest bedroom.

Our master shower has 2 shower heads and we have a claw foot tub that's not too big-55 gallon capacity I believe.

I'm a little nervous about having a tank on the second floor, but my builder assures me there will be a pan/drain. Any thoughts on this?

yes - install a water shut off sensor which you can find at www.smarthome.com. These sensors will detect water on the floor and sound an alarm. They will also shut off the water feeding the tank. The last thing you want is a water issue on the second floor - it can be distasterous. if it is a big leak, the floor drain will most likely not handle the water flow.

http://www.smarthome.com/7115H3/Water-Heater-Shutoff-1-25-Inch-Valve/p.aspx

Just wanted to chime in if you are considering tankless. Like another poster here we have a rather long house (140ft). Because of this we also chose two tankless units, one on each end of the house. They are the correct size for our needs and were wonderful...for as long as they worked.
Our first two units were from a company called SETS which was actually endorsed by NASA and used on the World Trade Center in 'shower-trailers' for the workers. Well, they turned out to be junk. By the time we contacted SETS we found they had gone out of business and were purchased by a company called Hubble. When contacted Hubble said they could not repair the SETS units but sold us two units with their "better technology" at a reduced cost. One of the units seems to be working fine after 3 months. It has instant hot water and the flow and temperature do not vary even during longer showers. On the second unit though one of the three heating elements went out after just 2 months. We were promised a new unit by Hubble and to date still have not received it...though we get promised almost daily that it's "In The Mail".

Please do your homework if you are considering a tankless.

The choice of water heater depends largely on where you live so it's difficult to have a "national" discussion about the possibilities.

Here in New England I prefer to use the NTI Matrix HVAC system which includes a hot water boiler, hot & cold fan-coil, tankless hot water, and optional fresh air ventilation. It's more expensive but well worth it.

Here is a link that might be useful: Matrix system

macv -

We are building in Western Mass - what does the NTI Matrix system typically cost? We are building a 2700 sq foot colonial revival. I have no idea what to look for in a HVAC system, and I don't want to get stuck with a "builder special".

we will have a Gas tankless heater I think with some models you can get a battery backup system (UPS Â Uninterrupted Power Supply) if needed

The matrix system does a lot so it's expensive. Here is one of the best installers of the system and he's just southwest of Worcester, MA:

Don Chaisson
Mark E. Meacham, Inc.
253A Worcester Road, Charlton, MA 01507-1501

800-328-7350
508-248-5551
fax 508-248-3366
Don's cell 1-774-696-5664

Thanks!