I don't have tankless because that is exactly what I read about the electric ones!

I can't see the electric units providing you enough hot water for 5000+ s.f. and 4 baths, especially in the winter months when the water is colder .

Id recommend a home run / manifold system if you're going tankless and locate it so that the runs are approx the same length.

I've never had a failure getting 140°F out of mine in the coldest winter weather but that's upper/central TX coast vs. SC of the OP's question. I can say that 140°F in a couple of those cases hit the maximum output capacity for the one usage task (washing machine).

Majority of usage tasks don't call for 140°F. Typical setpoint for a tank unit is 120°F. And it's doubtful that anyone stands under a 120°F flow for showering. My showering temp is 102°F. Some low-flow showers and faucets may run as low as 1.1 to 1.5 GPM at full-on.

Even if a given tankless can't reach the full setpoint, say 125°F, under a multiple-task, high-flow output and/or extra-cold-temp input situation, that doesn't mean there won't be *any* heated water .... it just won't be the full 125°F.

A 5,800 sq ft house with 4.5 baths needs to have more than one water heater due to the (presumed) layout distances, whether tank or tankless.

http://www.greenbuildingadvisor.com/community/forum/general-questions/39254/should-i-install-electric-tankless-hot-water-heat-pump-water

Look for the discussion of heat pump hot water heaters.

Unfortunately ATI is no longer producing.

http://hvac-talk.com/vbb/showthread.php?1714901-RIP-Air-Generate-Water-Heaters

http://www.stiebel-eltron-usa.com/pdf/brochure_accelera.pdf

https://www.gpconservation.com/ge-geospring-geh80dfejsr.html

Thanks to all for the in depth analysis. After reading the article posted by dan, I'm now leaning towards the heat pump water heater (the accelera noted above) -- I didn't even know that was an option until I saw noted above! Seems to satisfy my desire to stay with electric, but also avoid the issue of capacity given my large house.

My question now is whether the Stiebel Accelera is the way to go or whether there are other brands I should consider. Some more background on our house might be helpful. My wife and I are retiring soon, so it will be just us two in the main floor, which has 1 master bedroom (with jacuzzi tub), powder room, laundry facility and kitchen. The basement (walk out) is the only other floor and will have 3 bedrooms with full baths. My daughter will be living with us in the lower floor for a few years, but then will likely move out when she gets married. So the lower floor will then be primarily used for guests, of which we expect to have fairly often.

Because of the low use (at times) of the lower floor, it is tempting to consider the tankless, but I don't think a tankless would keep up with three showers, if they happen to be used at same time. So now I'm thinking about potentially two of the heat pump varieties. Perhaps the 80 gallon Accelera for the main floor and the 50 gallon for the lower floor? Or because I might have 3 showers going at same time on lower floor, would I need to consider two 80 gallon tanks? They are fairly expensive, so don't want to overdo it if I can help it.

Thanks for the advice! This forum is very helpful!!!

dd - I think you may be suffering from analysis paralysis.

Two heatpump are going to cost you a fortune. Then have you considered all the heat that they put off ? Even if you mount them in the garage all the heat they put off is going to suck in the Upstate from about April to Late Oct.

Then there's all that hot water sitting around when you're not using it. Why wouldn't you go with a gas tankless or two??? Propane is relatively cheap, especially if you fill your tank in the off season and they can be buried .

Soemthing like rinnai's largest unit is 98% efficient and will easily produce enough hot water for three showers at the same time. Make provision in your mechanical room for a second one, and you'll have unlimited hot water for four showers and the DW and laundry. I doubt youll need the second one.

Ive got a place I the upstate similar to what you describe and have gone with a tankless. Have not had an issue needing hot water for a house of 6-8 usually. Four showers, three of which are multifeatured, a 110 gallon tub, commercial washer, two dishwashers, and hosebibs that are plumbed for hot.

Now, the unit won't supply all of those running at the same time but we've never had a complaint that anyone doesn't have hot water for a shower or bath even when everyone is getting ready to go out at the same time. I am prepared to add a second unit if habits change and someone's shower gets starved for hot water with a full house.

I think you have dreams of off the grid livin, and that's not really practical with a 5000sf house with a swimming pool tub , four showers and 400 amp service . I doubt an afforadable solar array is going to supply enough juice for your heatpumps, and other needs too and even then itll prob. be the size of of a small farm.

Spend your money on foam insulation, LED lighting, and roofing that combats the SC sun and you'll see low monthly energy bills without looking like a science project . I'll likely cost less capital too.

You might also want to cross post this in the plumbing forum:

http://ths.gardenweb.com/forums/plumbing

GE also has two heat pump water heaters.

You are dedicating a lot of roof or outboard space to solar panels. If anything is left you have the option of using solar water heating panels as another source for hot water. Cutting out the middle man old school solar.

I still stand by my comment that the house is too big to make solar practical for anything but a conversation piece.

Just do some "simple math"! Take your average electric bill for a year, multiply it by 20, and compare this to the cost of the solar.

At retirement age, you will NEVER get your money back from the cost of solar, even younger folks won't. By the time the lease is up in 20 years the solar will need to be replaced.

As Xedos posted, spend your money on LED Lights, Induction cooking, efficient windows and doors, and you will be far ahead. Now how do I know that?

I have a new neighbor that moved in two houses north of me. The house was equipped with solar. Being the curious type, when they had an "Open House Party", I asked him about his electric bill. He says "good news/bad news" Electric bill from Electric company was $13, buttttttt the electric bill from the solar company was $403 (they charge per kw/hr) to pay for the lease. My typical electric bill is $60, and that's for warm sunny Calif, in the summer.

Whilst on the subject of tankless water heaters, my next door neighbor has had 2 in the last ten years now. He was at first quoted $6400.00 to replace the first one, but shopped around and found one for $2400.00, so BE CAREFUL, there are a lotta ripoff artists out there selling tankless water heaters.

We still have the tank water heater, replaced it after 12 years or so and it cost us less than a grand, couple this with the fact that there are Many and I mean many compliants about cold showers with tankless, couple that with the fact that when I was in the bank and told the teller I was thinking "tankless", the person behind me spoke up, Oh don't do that, My sister did and hates it.

Well, that and reviews cured me of any tankless thoughts. I can set my water heater anywhere I want, and I always have hot water---Love that Freedom!

Gary

"I can set my water heater anywhere I want, and I always have hot water ..."

Same here. :-)

Well, that's true as long as we don't forgets about our "delicate Miele dishwashers", and the intake valves, ya thinks? Mine is connected to the hot water side, but I've never had a problem, alto the DW is rarely used.

Gary

It all depends on if you have propane or natural gas. If you have natural gas then it will be cheaper to operate, if you have propane then the heat pump will be cheaper. I also would advise to skip the solar if you are doing it to save money; insulation, energy efficient appliances/lighting,and efficient HVAC will be your best bet. In fact skipping solar all together and installing a geothermal HVAC and hot water system will save you more money in the long run

Good advice, Malba.

I decided to "bone up" again on Solar, since I haven't studied it for a couple of years. I highly suggest the OP does the same. These "Leases" are a complete ripoff, they even get to keep what ever incentives various govt agencies may give you. They use the cheapest and oldest technology, and they DO NOT Want to sell you one as the leases are soooo lucrative. If you convince them to sell you one, they typically mark it up at least double the price of what the current market value is. And "current market value" is not that easy to determine, for example, google the price of a 10Kw system and see how many "actual dollar amounts" you get, (I got none).

There are articles that state Solar will drop dramatically in price in the next 2 years, also much more efficient ones are being developed, along with better storage batteries, (lithium Ion, instead of the old style car lead acid batteries).

So I do hope our posts here, and least encourage the OP to really do the homework on both Solar energy, as well as the best way to heat water, in their own particular area.

Gary

My 3,000 square foot single story house has three water heaters. A 50 Gallon gas unit in each end of the house for high demand areas and a 10 gallon electric for the kitchen. Since modern dishwashers run on cold water, the electric just runs the kitchen sink.

The natural gas bill to run two 50 gallon water heaters is $13-$15 per month. How long would it pay to recover the money on gas tankless? Forever, because the money saved won't even cover the additional maintenance and shorter life of tankless.

Check the costs of utilities in your area and don't discount the money saved by buying a high quality tank unit with good insulation.

I have a tankless water heater. I was initially scared off tankless because of statements like Dodges about cold water sandwiches and never having hot water. The tankless replaced a 40gal 25year old tank heater that was installed in a doorway. I replaced it with a Rinnai tankless water heater rated at 9.8gal/min at a 30degree rise. I have three full bathrooms with three adults who work and go to school all around the same time. I also always have guess who stay for a month at a time. I replaced my master shower valve because it stopped working a week before my tankless was installed. The new valve is a thermostatic valve. I set the temperature in my shower, step in within 10secs of starting the shower and never have a problem or even a small change in temperature. The unit comes with a built in recirculation unit that can be programmed. My shower heads have a max flow rate of 2.5gpm and a tub with a flow rate of 6gpm. The tankless is set to 120F and I have a Miele DW. Just replaced a 13yr old machine with a newer lumens. I had no issue with my intake valve. I write all this to say based on my experience, I would be hard pressed to go back to a tanked unit. The other bathrooms still have older pressure balanced valves and have no issue with the tankless either. This will be my first winter with the unit, so I will see the impact of going down to 5.5gpm at a 50degree rise. I am thinking I can now turn the water temp down to 105 degrees. My dishwasher and three washers heat their own water so incoming water temp is not a big deal just longer washer times which is preferred for the profile washes in the washers.

I agree that for a house this size, solar may not add value or efficiency. Consider R50 insulation in your roof, R32 in your walls, Led lighting, water saving shower options, a properly sized HVAC configuration, high quality triple paned high solar heat gain windows in the appropriate location, energy recovery ventilation system, etc

Good luck!

When I did my calcs for the upstate house propane was not more than electricity. Should be noted that we have 2500 or 4000 gallon tank and fill it in the summer when rates are silly low. Part of the infrastructure cost was spread out because I was already doing propane for cooking, fireplaces, and generators. If you were only getting it for hot water , prob won't make sense.

A blanket statement like Malbas isn't very useful because everyone's energy cost and energy consumption is so widely variable to be useless. If you are buying electricity in the Northeast you're getting raped compared to the cheap hydro power I have access to in the southeast.

I set my tankless heaters at 120 and never run out of hot water either. And my crowd takes 30 min. showers as a routine many days and some are two or more heads running at once.

Garys tank satisfies him I'm sure , but at my place it would be a disaster. My shower uses 15+ gpm - that'd be a ten minute shower with an 80 gallon tank and then there is basically no hot water for an hour. If someone took a shower before me, I'm down to five or less . If I take a tub at over 100 gallons, no one gets a shower of any length for an hour.

Now , I realize not everyone has a small swimming pool for a tub or car wash showers , or spends 30 mins. in them - but that's my point. Everyone's needs and demands are different. So, figure out what those are and have someone design systems to meet those objectives.

A 40 gallon electric tank heater that costs $500 installed is good enough for much of America. Prob. doesn't fit the bill for most of the houzz/GW crowd.

Shorter life???

you let me know Greg when your tank rusts out and I'll let you know if my tankless has been replaced.

You also need maintence on your tank heater too ! You should be draining the sludge out of the bottom periodically and if you have an electric, replacing the anode rod. That could be frequent , depending on how good or crappy your water is. So let's not mislead people that tank heaters are maintence free.

Payback is a fairly simple calculation based on your local energy rates and the capital cost of equipment and install.

Pro - did I read correctly ? You have three washing machines ?

Yes Xedos. Stuff happens. Stop judging me:-(. It was all Craigslist fault!!!

xedos,

One is 25 years old at the end of this year in another house, the two in my home are 17.5 years old. Bradford White high end units. And yes, I do drain them once a year. Two friends that replaced theirs with tankless at about the same time have had to replace them although I think they both lasted more than 10 years. Their maintenance is way higher with one needing a controller and fan and both needing descaling at least once a year. That is a bit more complicated than just draining a water heater, which just about any homeowner can do.

I did use a tankless in a vacation house where it made sense with intermittent high demand and then no use for a month or two at a time.

To be clear, I'm not saying tankless never make sense. I'm just saying don't assume they are always the right choice. You have to investigate each situation individually.

Not judging you pro, just found it curious as that's an appliance that people rarely have multiples of.

Greg, I agree that it's a case by case basis.

A homeowner that can drain their tank can de scale too. Sometimes less work because the drains are right under the units in many cases. The rest is just two hoses and two levers.

I know Xedos. Just great deals on two Miele washers and one extra dryer. So I have three washers and two dryers. Everyone one in the household has rheir own washer:-)

Iagree that the descaling is much easier for a tankless than draining a 40gal tank especially since my tank was in a doorway.

@xedos, yes my statement was somewhat of a generalization. However South Carolina is known to have pretty cheap electricity therefore it is highly improbable that propane will be cheaper than electricity for hot water, heat or anything else. Especially once oil prices start to rise, and electric prices are less related to oil than propane. The cheap electricity also makes solar a difficult proposition from an economic standpoint.

My recommendation to the OP would stand...if only propane is available use a heat pump water heater, and a geothermal or high efficiency (i.e. greenspeed) heat pump for heat/ac.

There's also the noise factor that no one has touched on . The heatpumps aren't near as quiet as a tankless , but wouldn't consider them loud either.

It is something to factor , but the largest decision point is volume. If you need more than 50-80 gallon in a hour - tankless is the way to go. It's as much about convenience or more than saving a few bucks.

"Only prob with the heatpump water heater is the latent heat it puts into the house."

???

Some heat is generated by operation of the compressor but isn't the intent of the process to remove heat from the immediate surrounding area and put it into the water inside of the tank?

Duh, massive brain f@rt.. I've had fridges on the brain this week as we're doing a remote compressor install for a fridges and wine unit .

Those produce heat into the room , not heatpumps as dadoes correctly points out.

heat pump water heaters cool the surrounding area as they operate.

Wow, thanks for all the good input. I didn't intend it to become a debate about solar, but found that interesting as well. I'm not familiar with the lease program that is mentioned. I'm looking to have an array installed that will be owned completely by me. I can get a 20kw system installed for about $60,000. There is a new Duke Energy program offering $1 rebate for each kw installed, so subtract $20,000. Then there are 55% state and federal tax credits, reducing the investment further to $18,000. The system should generate about $2,500 in energy per year (assuming 9 cents per kwh), resulting in about a 7 year payback. There is also potentially a benefit I can derive from depreciating the asset, but am not sure that is allowed, so need to check with my tax expert. I think the main different between now and before is the $1 Duke rebate. Without that, I agree the payback period would be too long (about 11 years), but a 7 year payback seems reasonable to me. There is always the possibility of repair costs in the first 7 years which could lengthen the period a bit, but the warranties on the panels at least are much longer than that. In any case, I think it is a worth a try.

With regard to the water heater question, I agree that two heat pump units might be too many, as the one in the basement might be idle for long times, so am not considering doing 1 heat pump (for the upstairs which will get used daily, but shouldn't use more than 80 gallons per hour as there is only 1 shower), and then a gas powered tankless for the basement. We have natural gas that will be already piped to the house for the stove/grille.

Any other thoughts or suggestions are welcome, thanks for the lively debate!