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Point-of-Use Electric Tankless Water Heaters

Now that I have installed several of these small, efficient water heaters in my house, I am an evangelical convert to the technology

Posted on Nov 26 2013 by Rick DuRapau

A couple of years ago, I was standing at my kitchen sink, idly waiting the minute or so for hot water, noticing my poor parched backyard. Central Texas was (and still is) in the death grip of a prolonged, severe drought. Our lakes are in really bad shape, and we are under very tight water restrictions.

Then suddenly, I had a mini epiphany: I’m wasting a lot of valuable water while I wait for hot water.

I’m certainly not the first to have this realization, but it just killed me to be wasting all that water. I did a little mental math: 2.5 gallons probably 10 times a day = 25 gallons a day, which = 750 gallons a month. At $4/1000 gallons, that's a minuscule financial hit — but hey, that’s just about a yard watering. It got me to thinking.

We've tried a lot of options

I’ve been tankless for years. My house of 32 years does not have access to natural gas. Consequently, we originally had an electric tank-style water heater. Back then, I didn’t know much about anything, but I knew that this was the worst way to make hot water. So, I did a little research, and bought a whole-house electric tankless water heater. All in all, it was not a great experience.

First, the rumor about whole-house electric tankless being expensive was true. Besides the roughly $2,000 for the unit, we had to do a pretty massive upgrade to the electrical system. I don’t remember how much the work cost, but it was a lot.

Second, the rumor about them not working very well was also true. But, we plowed on. I may have been driven, to some degree, by the fact I was going to inherit the water heater closet for my cramped shop. Not a small thing, indeed.

We went through several models, and performance was always less than stellar. My family grew weary of my standard response to their complaints: “Hey, there are people in the world that don’t have any hot water.” This did not play well with teenagers (or wives). At the time of the incident above, we were actually using a propane-powered tankless system, fed from propane cylinders. True story. That heater provided much better performance, but it was definitely a bummer when the propane tank ran out during a shower! My family was always mad at me, but by now, it was way too late to give my tricked-out closet back to some water heater.

A light bulb goes off

We happen to own a little cottage near the lake that we rent out. It had a small 40-gallon water heater that always smelled like rotten eggs. A while back, when the water heater croaked, I did some research, and replaced it with a small (10”x8”x3”) electric tankless unit from Niagara called a Titan N-120. It’s made in America, got pretty good reviews, and was a piece of cake to install. The renter loves the extra space in the tiny kitchen, loves the instant hot water, and is happy to have the rotten eggs smell gone.

I am an inventor of sorts — at least that’s how I’ve made my living for the last 20 years. My most famous product was the original plastic folding sawhorse called StoreHorse. That was a long time ago, and they are now mostly cheap knockoffs. I don’t mean to cast myself as some prolific genius type, but my point is that, almost by definition, as an inventor, I’ve always had a certain lack of respect for conventional wisdom. You won’t get far in this business doing things the way they’ve always been done.

So now, back to me standing at my kitchen window watching the grass die while perfectly good water goes down the drain. It seems like I decided then and there to go on a campaign to place a POUET — a point-of-use electric tankless water heater — at every location where we need hot water.

The driver was not to save money on my water bill, nor was it to save money on my electric bill; it was to save water. Yes, I am well aware that my 750 gallons a month is the proverbial drop in the bucket (pun intended), but I just thought it would be a good thing, and that’s just the way I am.

Small, medium, and large

Luckily, I am an extreme do-it-yourselfer. I did my own wiring and plumbing. It turns out that the work was really pretty easy.

I bought an assortment of seven POUETs; some from Craigslist, some from Amazon, and some from eBay. The size of the units ran the gamut.

At the small end of the gamut was a simple 110-volt, 2.4-kW, 20-amp Eemax unit that I installed in the downstairs half bath. With very little ability to raise the temperature, but with the included extreme flow restricting aerator, washing hands is all it needs to be: just OK.

In the middle of the gamut was a new Niagra Titan N120 that I bought off of eBay for about $220. At 220 volts, and drawing 54 amps, it took running a new 6/2 cable in a conduit outside the house. I installed the unit over the showerhead in the tub in the kids' bathroom, and I hooked it up to the sink as well. The kids say it’s the best hot water they can remember ever having in this house. I painted the unit, because frankly it was pretty ugly. Maybe it’s still a bit ugly, but I’ve always been a “form follows function” kind of a guy.

At the furthest extreme in the gamut were two Titan units that I installed in series, again over the showerhead in the tub, in the master bathroom. The reason I installed two is that my wife likes to take scalding (and I really mean scalding) baths, while I take showers. Each of the Titans has four settings or buttons. When she takes a bath, she turns on all eight clicks. When I take a shower in the winter, I turn one unit completely off, and the other on about two or three clicks. In the summer, I only use one click, and I wish there was a way to use half of that.

An end to wasted water and wasted energy

Now, I am an evangelical POUET convert.

Currently, my son and I are remodeling his new older house, and we are using POUET water heaters for the house. One of my buddies, who has been in the biz for years, says I’m @#$%&ing crazy. “Have you ever stood outside and watched the meter spin when that thing is on?” he says. Well, I say that’s conventional wisdom talking. I say that it takes the same amount of energy whether you do it fast or slow. Physics is physics.

What’s more, a non-tankless (see, that’s convert talk) system suffers from all the familiar stuff like stand-by losses, cold pipes carrying hot water, hot water being left stranded, etc. But, it’s not just about savings; there is so much more to it, like:

  • Having hot water before you can even fill a glass is a wonderful amenity. It’s like a garage door opener: once you have one, you can’t go back. How many times have you turned on the hot water to wash your hands, and then given up on the wait and just washed them with cold water? Talk about waste — all that hot water summoned, then abandoned. One of the harder habits to break is the routine we all do: turn on the shower, then go do something else while you wait for the hot water. With a POUET heater, the water is hot before I can get around the curtain.
  • Having the ability to adjust the water temperature on the spot is another great feature. On my son’s house, I am working to make all the units as accessible as possible. While he’s a convert, he still is not quite on board with putting the units out in plain sight. But, with what I know now, it seems near criminal to use the energy to heat the water up, then dilute it with cold water. A perfect system allows you to have the hot water you want without using the cold water valve.
  • If a heater goes out (which should seldom happen) you are not left dead in the water (another intended pun). And, replacement is relatively easy.
  • There is, of course, the well-known advantage of endless hot water.
  • If you are installing a POUET heater in a new build, or an extensive remodel, you only have to run a single water line.
  • The units can go just about anywhere: no flues, no fumes, no vents. Some jurisdictions may try to apply “tanked” codes to tankless heaters, but that’s all part of the learning process.
  • They are darn near 100% efficient. This does not address the debate about the inefficiencies of plant-generated electricity, but the fact is that virtually all of the power goes to raising the water temperature.

For utilities, there are time-of-use issues

Now, there is one downside that I cannot address: “peak demand.” Power companies will probably not, um, ... embrace this idea. They will see all those homes, all spiking the system with their morning showers, all at the same time. I don’t know, I’m not smart enough to know how bad that will be. But, I say, maybe it should be weighed against all those homes not wasting 10,000 gallons a year. Here and now, with the acute shortage of water, it might be a worthy tradeoff.

On a recent AIA home tour, I queried several of the designers and builders of touted “green” homes about POUET water heaters. They all wanted to discuss their state-of-the-art recirculation systems. To me, POUET is easier, cheaper, and more efficient.

After all these years of lamenting the lack of gas in my home to heat water, I would now choose POUET over some gas-fired system.

Someday, I think that POUET will be “conventional wisdom.” In the meantime, my yard is still parched.

Rick DuRapau is a regular guy who tends to see things a little differently. He lives in Austin, Texas, with his exceedingly patient wife of 37 years.


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  1. Rick DuRapau

1.
Nov 26, 2013 10:18 AM ET

Thanks for this testimonial.
by j wing

Thanks for this testimonial. I've used POUET in international travel (and loved it), but never in the USA. The ugly factor is huge, I think, but the heaters can be easily hidden in the adjoing closet or in a wall-hung cabinet nearby.


2.
Nov 26, 2013 1:23 PM ET

Don't sweat the time of use peak issues in Austin...
by Dana Dorsett

Austin TX has one of the most forward thinking local utilities anywhere, and the rate at which they are implementing demand response and distributed generation (mostly rooftop PV solar), the distributed storage to manage peaks that exceed the already implemented demand response is bound to come.

Charging electric cars with "dumb" charging systems rather than demand-response smart chargers is already becoming a bigger infrastructure issue than tankless point of use heater ever could be in neighborhoods where the density of electric cars has hit the critical point. Those neighborhoods are pretty few in number at the moment, but will be pretty common in 5 years. But if there is a utility anywhere in the US up to the challenge of managing it, Austin is the place to be!


3.
Nov 26, 2013 5:11 PM ET

another option
by Brent Eubanks

Here's another way to get around the water waste of running the hot line: push-button-activated recirculation pumps
http://www.gothotwater.com/

I'm not affiliated with the company; just a happy customer.


4.
Nov 26, 2013 5:21 PM ET

Thank you!
by Gordon Taylor

If you are really the inventor of the StoreHorse, then this message is long overdue. When I got your product (two of them) from Costco, way back when, I immediately wanted to write to the company and thank you for inventing it. I never got around to doing that, and now here you are. Thank you! You really changed the world, Rick, and for the better. Your design should be enshrined in the Museum of Modern Art. I mean it. It's amazing. I still have my original pair of StoreHorses, one which is slightly narrower than the other after I stupidly lopped it off with a circular saw. I expect I'll have them when I die.


5.
Nov 26, 2013 5:24 PM ET

Edited Nov 26, 2013 5:24 PM ET.

Love my tankless unit
by Kathlene Fleckenstein

I remodeled the owners unit in my duplex a few years ago. Gutted the kitchen and bath. Because the apartment is upstairs, the kitchen doesn't have full wall height. I wanted to get rid of the water tank to free up storage space under the counter, so went to a medium sized electric tankless unit mounted under the kitchen sink. Had to run a second 220 line, but the place was torn apart anyway so it wasn't a big deal. Decided to just go with the single unit as the bathroom is located right next to the kitchen.

I did it only to add storage, but with only myself living in the apartment I got the added advantage of saving $20/mo on my electric bill! I live in the NE where electric rates are high, and have nobody else using hot water, so others will probably not see this savings. But it was a nice bonus for me!


6.
Nov 26, 2013 9:29 PM ET

Heat pump water heaters
by Nick Welch

It seems like the next big thing in water heating is heat pump water heaters. But they're the antithesis of tankless heaters -- they heat slowly, and benefit from not just a tank, but a bigger than average tank. While tankless heaters may save you a few percent on standby losses, and a few bucks in water per month, a HPWH will save you something like 50%.


7.
Nov 27, 2013 2:46 PM ET

HPWH and tankless
by Michael McKinley

As it happens, I am both camps. Living in sunny CA, with mild winters, a HPWH works great for me. Factor in some rooftopPV to make it (the house) near net zero, and since I don't have natural gas alternative, it's a greatr option. With added insulation and air sealing to limit space heat/cool, the hot water is a major part of the total bill.
BUT; I am on a well, with very low output. So, like Rick, watching water run down the drain kills me. With the master bath some 50 feet from the HPWH, I have added in the instant tankless. It eats up juice at first, but saves water. Once the hot water from HPWH arrives, less juice needed at the tankless. CA title 24 really penalizes me for all this (there is no credit for PV, and any electrical use is bad in title 24; propane scores better than electrical, even though propane is way more expensive). The HPWH is near the kitchen, downstairs bath, and 1/2 bath, with runs averaging under 15 feet, so less waste there.


8.
Nov 27, 2013 8:50 PM ET

Don't ignore solar
by Michael Armstrong

I love the solar collector and a large tank, coupled with on-demand circulators. In Florida, at least, it's free, nearly-instant, very hot (160° at the dishwasher) water, and lots of it.


9.
Nov 28, 2013 5:24 AM ET

The downsides...
by Dennis Heidner

There are three times of the day when it is most likely that a shower or bath will be taken. Before work, after getting home from work, or before going to bed. They also happen to correspond with the beginning of the ramp of electrical demand, the beginning of peak electrical demand and the tail of the evening peak demand.

The comment that "Physics is physics" is true... but there is a difference between average and peak demands. Utilities build the generation plants based on peak demand not the average. The electric rates for residential customers are higher than the industrial customers for many reasons - and one is that residential loads are very "peaky". Peaky loads drive the utility schedulers/dispatchers crazy. The ISO's like to use those evening peaks to create artistic graphs of ducks. (google California ISO Duck) / http://www.caiso.com/Documents/Presentation-Mark_Rothleder_CaliforniaISO...

Shifting residential customers to electric resistance heat alone and not moderating it with solar thermal when it is available adds the water resource problems. Nuclear and coal power plants both use water for cooling. If you are lucky the plants may be on the coast and able to draw in some of that warm Gulf salt water to cool the plants. But if not - it means competing with the same critical water resources that could be used for crop irrigation.

The heater costs is lower - but when you add in the larger electric service cabling, ground fault breakers for the heaters in the service panel and new circuit runs - some of that low cost disappears.

In the southern US, you really do want the instant water heating appliance to bring the potable water to a 150F+l and temper it down before taking a shower. Legionella can thrive in water lines - especially if the water stagnates for a few days and the temps in the house are in the range of 70F-100F. That flash heating and remixing before creating the mist that you breath while taking a shower might be a life saver.

I know it sounds like I hate the instant heaters - I don't -- in fact I use one for the coffee and tea hot water. I have a gas tankless heater. The electric instant tankless heaters are great answers for many problems. The DOE Challenge Home presentations I believe also remind the designers that they are good options. But good things can have downsides and if we forget them - we often get burnt later when there is wide spread adoption. Rooftop solarPV and the battles over the value of solar is an example. Utilities didn't care when the quantity was low - but as solarPV penetration into the market increased - they became very concerned and panicky. A wide spread switch to the instant heaters for bath needs is likely to result in larger residential demand peaks -- and rate changes by utilities will be adopted to alter those peaks.

In Texas, I would have thought solar hot water or hot water heat pumps would be the first choices. In hot humid climates the HPHW can also provide some dehumidification. If space is a limitation - the approach taken by Middlebury at this years (2013) SolarDeclathon - makes good sense... combine small storage tank with instant heaters (Middlebury was all electric -- no solar). Their system smooths out the peak demands by heating a smaller quantity that is stored and readily available... it provides the hand wash needs - when exhausted - the instant tankless heaters provides the load - without intervention by the residents. If solar is available -- Texas right? -- then you could pick up some of that base heat from the sun.


10.
Nov 28, 2013 2:04 PM ET

Mixing
by Geoff Briggs

Does mixing in cold water to moderate temperature really increase energy use? Given that the fixture delivers a fixed amount of water, mixing hot and cold means less hot water is used per minute. Or is the problem that the electricity demand of the POUET is the same regardless of flow? I ask because I have a use case where these would be ideal but do not want them in plain sight. Thanks.


11.
Nov 28, 2013 4:49 PM ET

Edited Nov 28, 2013 4:50 PM ET.

RE:Mixing
by Dennis Heidner

Mixing doesn't really make that much difference in the energy use - if the only choice is a fixed output temperature from the tankless heater. In a tankless heater like a Titans there may be some losses - the heating chamber probably losses a little energy via radiation... but the loses would be small.

I believe Rick's comment was more in line with wouldn't it be nice if you wanted 105F water for shower - that the tankless heater only used just enough energy to bring the water temperature to 105F. That would save the need for second cold water pipe at the shower/tub. Assuming you are using a shower with a flow re stricter the volume of water would be the same (as measured entering the house).

The Titans do measure the input and output temperatures of the water. It measures flow rate and the heat added is (based on their brochure) adjusted to match the desired temp. It looks like they have a microprocessor and the heating element is controlled via a TRIAC (think light dimmer).

The peak electrical loads vary with the inlet water temperature and the flow. The Titan 120 can use 11kW when heating cold water (winter) to 120F.


12.
Dec 3, 2013 5:04 PM ET

Gary Klein has figured some of this out already
by Kevin Dickson, MSME

"I’m wasting a lot of valuable water while I wait for hot water." You're also wasting a lot of your valuable time.

Gary Klein, the hot water guru, has a solution that I think is better and cheaper than scattering these appliances all over the house. Basically, you use home run piping with low-water-volume 3/8" PEX: http://greenbuildingindenver.blogspot.com/2012/07/plumbing-efficiency-in...

"“peak demand.” Power companies will probably not, um, ... embrace this idea" -- Gary has convinced me that on demand resistance water heaters are a good option. In reality, the peak load due to morning showering in a given neighborhood is statistically flat enough not to cause problems. Basically, people in a given neighborhood don't actually shower at the same time.


13.
Dec 7, 2013 1:32 PM ET

Edited Dec 8, 2013 9:04 PM ET.

Optimising Point of Use Electric Tankless Water heater install
by JAMES KREYLING

Mentioned in the past, but worth reminding is the incorporation of a Gravity Film Drain water Heat Exchanger (GFX) such as a "PowerPipe" into the DHW flow sequence for tempering the incoming water supply to the water heaters. . As the temperature rise and flow rate capacity of most POUET heaters is fairly limited, designing a layout to make use of balanced flow tempered by the GFX can save up to about 50% of the temperature rise demand and of the electrical consumption for the flow. The greatest opportunity for this is, of course, for showers. Design your home to stack your baths, Install a PowerPipe of at least 5' length (preferably 6' x 3") and plumb your home with cold-only PEX, POUET water heaters, ALSO incorporate an NFPA 13D Multi-Purpose residential sprinkler system, into the PEX cold water layout and you have a nifty and highly satisfactory water system that gives you fire protection and reduces your home insurance premiums as well. Of course it is easy for me to recommend the multiple POUET heaters since I am an electrician and the prospect of running 3 or 4-60 amp 240 volt feeders to the POUET water heaters is not a daunting prospect for me. 200A service recommended.
I am currently working on finalizing my plans for a new SIP "Pretty Good House" to be built on a nice piece of Southern exposure land in coastal Massachusetts in the spring. I plan on using this plumbing method, planning on 3-12KW digital SCR controlled POUET units. Our city water and sewer costs are very high, and such a plumbing plan is hoped to contain the high bills I have seen in the past in the home I am now in. (But then the teenager and his 10 minute showers can be a challenge to the conservation scheme...) I welcome feedback and challenges to my design scheme proposal. Throw them at me and let me see if I can defend the plan...


14.
Apr 13, 2014 4:58 PM ET

Thank you
by Jennifer Hogan

This is exactly what I have been contemplating. I will be living in a 2 person home.

The storage closet for the water heater encroaches into the master bath. There is no option for natural gas. The hot water tank that is currently in the home is not large enough to fill the large spa tub. It is the only bathtub in the house. The master bath doesn't have room for a tub.

But all I keep hearing is the issues with the whole house electric tankless systems. I read comments from people talking about the point of service units that they had in europe and how well those worked in comparison.

I am seriously thinkng that this may be the right answer. Thanks for sharing your experience and confirming that this is a viable alternative solution.


15.
Dec 3, 2014 5:02 PM ET

POUET water heater
by Patricia Thames

I live in Northern California. We go through 6 year drought cycles...darn LA. First of all, for all the water you are watching go down the drain...shame on you. There is this thing called a bucket and you collect all the clean water while you wait and put it out on the plants. My parents used to run the second wash rinse out the window in a hose and onto the grass.
Europe has been using this kind of heating system for years and years. I agree about not worrying about the peak time. The energy companies want us to stay with that tank. My PG&E bill went from $65 to $13 when my hot water heater went out. The tank was just sitting out in the garage perking away during my work time and at night.
When I spoke to a tankless companies they discourage you from going to this system of multi-units. I would like to know how you gauged which unit would do the correct amount of service, without over building. Both of my bathrooms are almost on the other side of the wall from the current water system, however my kitchen is across the other side of the downstairs about 25ft. I was going to put a unit on the outside wall for the kitchen only. I was told it would be too expensive.


16.
Feb 17, 2015 1:15 PM ET

A high performance builder
by David Jones

A high performance builder for 25 years, we specified our first pouet water heater recently in a guest apartment over a garage. I was impressed. It is being used as a booster while the hot water from the main house system arrives.

Now working on specs for a very small, very inexpensive, zero energy home. No basement to put the heat pump water heater. Utility closet space very limited. Don't really want to introduce burning any fossil fuels if I can avoid it.

Had been considering POUET, but ability to get adequate temperature rise was my concern. Live in NW Connecticut where incoming water temps can be very low. Using these devices in series is a great solution! (Wondering if this method would be discouraged by manufacturer)

Love the idea that only one water line is required! Hadn't considered that.


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