# When does purchasing a solar water heater make sense?



## Boris (Nov 18, 2010)

I hope my calculation will be useful for the members of this forum.


Calculation of payback period for Integrated Tank Solar Collectors/Thermosyphon Solar Hot Water Systems in comparison with propane and natural gas 

Initial data:
- The annual average performances for one collector with 30 tubes is roughly 11,242,000 BTUs in warm climate and 8,760,000 BTUs in cold climate.
- One gallon of propane can produce approximately 91,600 BTUs.
- One cubic foot of natural gas can produce approximately 1000 BTUs.
- One cubic meter/metre of natural gas can produce approximately 36000 BTUs.
- One cubic meter/metre is equivalent to 35.3 cubic feet.
- August 2011 price of propane/LPG (for my area):$3.25/per gallon. Updated Propane prices are here- 2010 USA national annual average residential natural gas price was $12 per thousand cubic feet (Mcf).
- 2010 Canada national annual average residential natural gas price was 25 cents for one cubic meter.

So, 123 gallons of propane (11,242,000 BTUs/91,600 BTUs per gallon) could be offset in warm climate and 96 gallons of propane (8,760,000 BTUs/91,600 BTUs per gallon) could be offset in cold climate. 
That leads to savings of about $399.75 (123 gal. x $3,25) in warm climate and $312(96 gal. x $3,25) in cold climate respectively. 

Or 11,242 cubic feet of natural gas (11,242,000 BTUs/1000 BTUs per cubic foot) could be offset in warm climate and 8,760 cubic feet of natural gas (8,760,000 BTUs/1000 BTUs per cubic feet) could be offset in cold climate. 
That leads to annual savings of about $135 (11,242/1000 x $12) in warm climateand respectively leads to savings of about $105 (8,760/1000 x $12) in cold climate.

To summarize, for areas where natural gas is used for water heating, and if you will spend around $4,000 for the simplest solar hot water system, the payback period (investment return period) is more than 17 years EVEN with application of federal tax credit and other state (province)/utility rebates in the warm climate and more than 20 years in the cold climate.

In Canada the natural gas is less expansive. 
Therefore the real savings are less attractiveIn real life, we should further reduce these numbers because of the losses that occur in solar storage tanks and transfer pipes.The result will be even worse for solar collectors with 25 or 20 tubes.

I posted new photos here:
http://www.beebehavior.com/solar_water_heaters.php

Boris Romanov


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## SolarGary (Sep 8, 2005)

Hi,
Thanks Boris.

One thing that your analysis assumes is that all the heat output from the system can always be used. A couple of people using 40 gallons total a day of hot water have a demand of about 20K BTU/day or 7.3 million BTU per year --so, they would not be able to make use of all the heat your sample system makes. Output in the winter and summer would be different, with the excesses being greater in the summer.
You don't allow for fuel price increases, which could be very substantial over those long payback periods you show.
It looks to me like your calculation assumes that the gas water heater is 100% efficient -- most of them are only about 60% efficient. In other words, the propane offset should be more like (123 gal)/(0.6 efic) = 205 gallons. That is, you would have to burn 205 gallons of propane in the water heater to make the 11.2 million BTU.


You can, of course, build your own system for about $1000, which cuts the payback period by a factor of 4, but takes some work.

http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm

Some examples:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm#Example1KSystems

The payback analysis I do for the $1K system shows about 3 years depending on fuel:
http://www.builditsolar.com/Experimental/PEXColDHW/Cost.htm
This is with no rebates and and no allowance for increasing fuel prices.

Gary


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## Boris (Nov 18, 2010)

Gary, 

Firstly,
- the &#8220;unused BTUs &#8220; were mentioned in &#8220;Maine disadvantages of Solar Collectors&#8221; of my web page. And my post was linked to this page.
- &#8220;Solar water heating systems require a conventional water heater as a backup water heating source to ensure hot water is available when solar energy is not. 
Expected Energy Savings Over Equipment Lifetime (20 Years) for the Solar (water heater) with Electric Back-Up&#8221; is up to $2,200 ONLY in the Mild-Hot climate or up to $110 ONLY annually ($2,200/20)
From: http://www.energystar.gov/ia/new_homes/features/WaterHtrs_062906.pdf

Secondly, I don&#8217;t believe in your opinion, because for many years you misinform people with your false calculations and statements similar to these:
&#8220;&#8230;Each day, the 500 gallon tank has started at around 85F, and ended the day at about 125F. So, the stored heat by per day is: 
Heat Stored = (500 gal)(8.3 lb/gal)(124F - 85F) (1 BTU/lb-F) = 162,000 BTU&#8230;
&#8230;I did make an estimate for the Mother Earth News article based on the performance up to the time I wrote the article that the system is saving me about 330 gallons of propane a year. I've not seen anything that would make me change that estimate. &#8230;&#8221;
From: http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Performance.htm

You stated &#8220;Each day&#8230;&#8221; But why you didn't say correctly: Each SUNNY day or Each Clear Day (in terms of SRCC classification)? 
Do you live in area without cloudy days or snow days? &#8230; 
Therefore, in my opinion you cannon store 162,000 BTU &#8220;Each day&#8230;&#8221;

According to your data your solar collector can produce 27, 000 BTUs per 40 sqft each day (162,000 BTU /6). But even modern glazed flat-plate solar collectors do not reach such characteristics.
And according to the SRCC the technical characteristics of ALL Glazed Flat-Plate collectors are very low during the cloudy days, especially in the cold climate.

You also stated: &#8220;&#8230;I will assume that the solar water heating will provide 75% of this, or 8.25 million BTU/year or 2400 KWH per year. I think that the system is likely to actually do better than this.&#8221;
http://www.builditsolar.com/Experimental/PEXColDHW/Cost.htm

In real life the annual average performances for the one modern TitanPowerPlus-SU2 Flat-Plate Solar Collector is about 5,986,000 BTUs in warm climate and about 3,522,250 BTUs in cold climate.



In addition you stated:&#8220;&#8230; The resulting collectors cost about 1/4 what commercial collectors cost -- a $5500 saving&#8230;&#8221;
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/collectors.htm

But you did not mention a labor cost and federal tax credit and other state (province)/utility rebates for the factory made certified collectors.

Boris Romanov


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## mightybooboo (Feb 10, 2004)

I think Garys' big advantage has been in designing and using systems,I myself put a lot of stock in his expertise.


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## bignugly (Jul 13, 2011)

I think too much stress is being placed on payback on investment. How about the reduction of your carbon footprint? How about reducing your dependency on companies you could at their desire, bankrupt you? We all have been living at the whim of the stock market speculators. I for one would like to have at least some control of what I do with my life. 
I really love it when people spout numbers trying to impress others with their intelligence. If you don't want to use solar,don't. If i want to, I will no matter what the so called payback time is.


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## SolarGary (Sep 8, 2005)

Hi Boris,

What I had in mind by responding to your calculation for solar water heater payback was that (in my opinion) it did not account for at least two very important things -- the actual efficiency of gas water heaters and the potential for significant increases in fuel costs over the long payback periods you show. Your calculation in effect assumes that gas water heaters produce heat with 100% efficiency when it fact its more like 60% -- this is an important difference and leads to a significantly longer payback period.

But, I want to answer the points you raise about some of the performance estimates from my systems just so there is no confusion.

You say: 
&#8220;&#8230;Each day, the 500 gallon tank has started at around 85F, and ended the day at about 125F. So, the stored heat by per day is: 
Heat Stored = (500 gal)(8.3 lb/gal)(124F - 85F) (1 BTU/lb-F) = 162,000 BTU&#8230;
&#8230;I did make an estimate for the Mother Earth News article based on the performance up to the time I wrote the article that the system is saving me about 330 gallons of propane a year. I've not seen anything that would make me change that estimate. &#8230;&#8221;
From: http://www.builditsolar.com/Projects...erformance.htm

The actual quote from the Mother Earth article is:
"Here is performance data for two sample
days from last winter.
Jan. 12, 2007: A very cold sunny day. At
10 a.m. when the collector started gathering
heat, the outside temperature was 20
below zero! The collector warmed the storage
tank water from a morning low temperature
of 85 degrees to 125 degrees in
the afternoon. This heat energy stored in
the water is the equivalent of 2 gallons of
propane burned in a furnace of typical (85
percent) efficiency.
Jan. 27, 2007: A typical sunny winter
day with a high of 30 degrees. The tank
warmed from a morning low of 85 degrees
to an afternoon high of 132 degrees. This
is the energy equivalent of 21&#8260;2 gallons of
propane burned in a typical furnace."


It seems to me that this makes it abundantly clear that these temperature rises are for sunny days -- it gives the actual dates and weather conditions on those days -- I don't know how I could have been more clear.

The web page you reference makes if very clear if you read the full page that the examples are for sunny days -- just read the "Update Feb 21" entry -- it starts with "Today was a sunny day."


You Say:
"I did make an estimate for the Mother Earth News article based on the performance up to the time I wrote the article that the system is saving me about 330 gallons of propane a year. I've not seen anything that would make me change that estimate. &#8230;&#8221;
From: http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Performance.htm

You stated &#8220;Each day&#8230;&#8221; But why you didn't say correctly: Each SUNNY day or Each Clear Day (in terms of SRCC classification)? 
Do you live in area without cloudy days or snow days? &#8230; 
Therefore, in my opinion you cannon store 162,000 BTU &#8220;Each day&#8230;&#8221;

The 330 gallons of propane yearly saving is most definitely not based on every day being sunny -- it is based on a reasonable fraction of days being sunny, part sunny, and cloudy (no output). It is also based on our actual space heating propane usage, which has dropped from 1650 gallons for the first year in our location down 780 gallons for 2009 and 850 gallons for 2010. These are actual usage which is very easy to record in our case as we have a big tank and only fill once a year since installing the system. Part of this saving is due to the solar heating system and part to insulation projects.
At some point, I would like to install better logging on the system and record its actual heat output for a full season, but until I do that I think the 330 gallons is a good estimate of the system savings, and is most certainly not based on 100% sunny days.

On a sunny day, the saving is about 160K btu, which is equivalent to burning about 2 gallons of propane in an 85% efficient furnace. Our heating season here is 8 months long -- if I had figured that every day was sunny, the yearly propane saving would have been (243 days)(2 gal/day) = 486 gallons.

You Say:
"According to your data your solar collector can produce 27, 000 BTUs per 40 sqft each day (162,000 BTU /6). But even modern glazed flat-plate solar collectors do not reach such characteristics.
And according to the SRCC the technical characteristics of ALL Glazed Flat-Plate collectors are very low during the cloudy days, especially in the cold climate."

This is just not correct. This is the SRCC report for the Heliodyne Gobi 40 sqft flat plate collector:
http://securedb.fsec.ucf.edu/srcc/coll_detail?srcc_id=2010115A
This collector is a typical, good quality flat plate collector. 

This is what the SRCC report shows for daily heat gains sunny through cloudy:
For class C it shows: 44.7K BTU sunny, 30.9K BTU mildly cldy, 17.2K cloudy
For class D it shows: 30.7K BTU sunny, 17.7K BTU mildly cldy, 5.7K cloudy

Solar space heating in SW MT is probably between class C and D -- and, by the way I would characterize SW MT as having pretty sunny winters -- that's why we moved here from Seattle 

This Heliodyne collector uses selectively coated fins and single glazing.
My Solar Shed collector uses a selectively coated commercial absorber plate with twinwall (double) glazing. Which do you think might be more efficient?

You Say:
"You also stated: &#8220;&#8230;I will assume that the solar water heating will provide 75% of this, or 8.25 million BTU/year or 2400 KWH per year. I think that the system is likely to actually do better than this.&#8221;
http://www.builditsolar.com/Experimental/PEXColDHW/Cost.htm

In real life the annual average performances for the one modern TitanPowerPlus-SU2 Flat-Plate Solar Collector is about 5,986,000 BTUs in warm climate and about 3,522,250 BTUs in cold climate."

The only TitanPowerPlus collector I could find in the SRCC ratings only has an area of 26 sqft. The analysis I did for a family of three clearly states and the cost includes a collector of 48 sqft. So, I don't see that the fact that a collector half the size only produces about half as much heat output as too surprising?

At any rate, the cost and economics page gives an analysis for a family of 3 as I thought this would be more typical than our system for just the two of us:
http://www.builditsolar.com/Experimental/PEXColDHW/Cost.htm
The cost analysis system uses a collector area of 48 sqft, which is a bit more than 15 sqft per person that is widely used by the industry. The cost analysis includes all the costs associated with the full 48 sqft. 

This is somewhat bigger than the $1K system we actually built because there are only two of us and our hot water needs are modest. Our system was carefully logged over a full year and produced a full year solar fraction that was well above 75% -- you can see the actual day by day plots of tank temperature for the full year here: http://www.builditsolar.com/Experimental/PEXColDHW/Performance.htm


You Say:
"In addition you stated:&#8220;&#8230; The resulting collectors cost about 1/4 what commercial collectors cost -- a $5500 saving&#8230;&#8221;
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/collectors.htm

But you did not mention a labor cost and federal tax credit and other state (province)/utility rebates for the factory made certified collectors."

Well, clearly the labor cost for a DIY system is zero -- and you get all the fun of building the system 

You keep mixing up the two systems I have there is a Solar Shed space heating system: http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm
And there is a $1K domestic water heating system:
http://www.builditsolar.com/Projects/SpaceHeating/DHWplusSpace/Main.htm

They are different, and have different cost savings.

For the solar water heating system, I think the savings is greater. While the price of commercially installed solar water heating systems varies with location and system size and complexity, $8000 is a very commonly quoted number. You can (and many people have) build a $1K for (surprise) $1000. So, the cost saving before rebates is more like $7000.
Why commercial system are so bloody expensive is (to me) one of life's mysteries, but they are.

On the rebates front, a DIY system does not qualify for federal rebates, so on a federal only basis, the commercial system that knocks about $2400 off the $7000 saving for doing the system yourself.

But, some states offer rebates that DIY systems do qualify for. We get a $500 rebate in MT on our system. This is half what it cost us!
I don't know what other states offer, but the http://www.dsireusa.org/index.cfm site can be used to check.

It is also possible to get the federal rebate on DIY systems by buying a collector that is SRCC certified -- the collector is the only part of the system that needs certification in order to get the 30% federal rebate on the full system cost. If you go through the numbers on this, it ends up costing a bit more than building everything yourself, but it saves the effort of building the collector.

I'm sure no one has gotten down this far, and I apologize for going on. I just wanted to make it clear that the numbers shown on my site and in the articles I've written are as honest and accurate as I can make them -- they are based almost all based on real measured performance, and where I can't provide actual performance I make it clear how I got the numbers.


Gary

Edit 7:17pm -- took out some repeated text.


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## Wisconsin Ann (Feb 27, 2007)

Gary, I got down to the end, and thank you for your very clear response  I particularly like it when someone can specify actual usage data instead of theoretical Makes it more "real". 

Interesting thread. Differences in style and thinking are always good. Some people prefer using readymade or conventional mechanics...others prefer working on a custom system that they can refine themselves. I know my partner really prefers building his own because that's what makes him happy  (the fact that he's a working mechanical engineer with a few decades of hands on experience in a prototyping research lab is helpful, too  )


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## Wisconsin Ann (Feb 27, 2007)

Boris,
I read your site. Well done reviews. very helpful explanations. Thank you. I've always thought you had some interesting things going in the regular Bee part of your site. Was unaware that you had branched out further. (I must have missed the "my energy efficient house" the last time I was on the site. )


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## artificer (Feb 26, 2007)

Gary:

Nice posts. (as always) I'm still confused about the OP's statements... is he for or against solar heating?

I don't understand how your observed data can be called mistaken. Bad data gathering? Mathmatical error? I think its a stretch to say that since you didn't use his wording, its wrong.

I want to build something like your systems for our off grid shed. Those 20 used 12'x4' doublewall polycarb pannels I have stored in the shed are calling me...

Michael


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## Boris (Nov 18, 2010)

bignugly, 

you stated: &#8220;&#8230;If you don't want to use solar, don&#8217;t&#8230;&#8221;
But as you can see here: http://www.beebehavior.com/solar_collector.php 
I&#8217;m not against solar. 

Gary,
The title of my current tread is &#8220;When does purchasing a solar water heater make sense?&#8221;, 
and the subtitle of my web page related to this tread is &#8220;Solar water heaters versus modern conventional water heaters&#8221;, but not versus DIY projects. 
Therefore I think your links, posted in my tread are nonsense.

In addition, I would like to once again stress - the technical characteristics of ALL Flat-Plate collectors are very low during the cloudy days, especially in the cold climate.

Gary - For me it&#8217;s very clear why you still did not post your two solar systems performances during cloudy (in SRCC definition) days.
Your data is a good confirmation of my statement. 
I think it&#8217;s very clear for everyone - 5,7K is very low compare to the 30,7K.
Therefore the further conversation with you about this matter is useless to me&#8230;

Wisconsin Ann, 
Thank you for your comments.


Here are some typical recommendations from manufacturers of solar collectors:
&#8220; - Flat Plate Solar Collectors typically cost less from the outset than Evacuated Tubes. However, the lower performance ratings in many climates, and increased maintenance and replacement costs mean that they are generally less cost-effective than Evacuated Tube Collectors.
-We recommend Flat Plate Solar Collectors to our clients who live in southern climates where freezing is unlikely, and where solar angles, and the amount of 
sunlight does not justify the increased investment of an Evacuated Tube Solar Collector.
-We recommend Evacuated Tube Solar Collectors for our clients anywhere where cold weather, and possible freezing is a significant factor in the weather.&#8221;
More details are here: http://solarhotwater.siliconsolar.com/pdfs/flat-plates-vs-evac-tubes.pdf

I will add more details related to my thread soon.

Boris Romanov


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## bignugly (Jul 13, 2011)

So Boris, what you are trying to do is sell a product. I totally misunderstood. Rather than cite facts and figures, why not just say your product works better for whatever reason.


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## Boris (Nov 18, 2010)

bignugly said:


> So Boris, what you are trying to do is sell a product. ...


Typical question from &#8220;brave&#8221; anonymous&#8230;

What product? There are many &#8220;products&#8221; on my web pages&#8230;
I do not sell anything.

I just would like to show how to avoid typical mistakes before purchasing any solar system, based on my knowledge and practical experience.


No more answers for the questions not related to this tread.

Boris Romanov


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## Wisconsin Ann (Feb 27, 2007)

> The title of my current tread is &#8220;When does purchasing a solar water heater make sense?&#8221;,
> and the subtitle of my web page related to this tread is &#8220;Solar water heaters versus modern conventional water heaters&#8221;, but not versus DIY projects.
> Therefore I think your links, posted in my tread are nonsense.


But Boris, don't you see..Gary was trying to point out some things in your analysis that are just flat out wrong. (he was trying to be tactful about it). You DO assume 100% efficiency..which isn't possible. And running your numbers showing that you do assume that makes your whole article lose credibility,and that's a shame because you have some good advice and comparisons. 

He also tried to get you to do some lower volume calculations..which you dismissed. 

In his first post all he tried to do was to show you and anyone reading this thread that there are DIY alternatives for those who don't have $8000 to plunk down for a store bought way to heat water. Always a problem for people on this forum...it's mainly made up of people who are on tight budgets.

Gary has a HUGE reputation (and justifiably so) among the world of Solar and alternative energy people around the country (and for all I know, world). He's on multiple sites, with a LOT of people using his plans and reporting back data.

For you to come on a forum and call him a liar is....not helpful to your cause.

If you don't want a discussion of your pontifications, don't start a thread. A forum is FOR discussion. Particularly a homesteading forum. It's for learning from and with each other.

oh, and you don't have to answer my post. I don't expect you to.

by the way...the snide way you respond to bignugly is totally uncalled for. he's no more anonymous than you are.


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## Boris (Nov 18, 2010)

This Gary's statement is related to my tread and I will comment it.



SolarGary said:


> So , that is a completely false statement for the modern gas water heaters.
> Once again, the title of my tread is âWhen does purchasing a solar water heater make sense?â ( âSolar water heaters versus modern conventional water heatersâ.)
> 
> Just one example to prove my statement.
> ...


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## zant (Dec 1, 2005)

We are putting together pieces for a solar hot water system-living in S.Al,it's silly not to use the sun-Like Gary's systems......word of caution with the naivien(sp)tankless...1.I've never seen a "endless HW system"-maybe if 1 or 2 people are frugally using-not a family with dishwasher,washer,showers going at once-many people bought into "endless"and became disappointed.2.In reading info-2 microprocessors are involved-how long will they last in a non air conditioned enviroment???Had a state of art washer/dryer blow computer boards(at [email protected] thanks)ALL of the appliance repair places I called asked-Are they in a room with AC-NO...well thats the problem...I bought used boards and dumped w/d.Vet near us had a 1200$ LG go bad after 5mnths-not in AC space...


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## mightybooboo (Feb 10, 2004)

98% efficient? Im not even buying into that no matter what they claim.

Boris,do have have factual PROOF from your own testing to back that up?


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## SolarGary (Sep 8, 2005)

Boris said:


> This Gary's statement is related to my tread and I will comment it.
> 
> 
> 
> ...


Hi Boris,
Well, I see what you are saying, but that water heater is a $1600 to $2600 water heater -- its certainly not typical of what people are buying these days.

The $300 to $400 gas water heaters that people typically buy at Home Depot etc and that represent by far the bulk of the sales have efficiencies around 60 to 65%. Wouldn't it make more sense to base your analysis on what people are actually buying/using?

The Navion condensing unit is an impressive water heater, but for the price difference between it and a regular water heater you could do a DIY solar water heating system and have nearly free solar heated water and still have money left over.


http://www.amazon.com/dp/B004PYEASU...e=asn&creative=395093&creativeASIN=B004PYEASU

http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053

Gary


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## Boris (Nov 18, 2010)

mightybooboo said:


> 98% efficient? Im not even buying into that no matter what they claim.
> Boris,do have have factual PROOF from your own testing to back that up?


This is the best proof:
âNavien America is an official Energy Star partner for tankless water heaterâ
From: "Navien America" brochure.

Boris Romanov


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## Boris (Nov 18, 2010)

SolarGary said:


> ...Well, I see what you are saying, but that water heater is a $1600 to $2600 water heater -- its certainly not typical of what people are buying these days.
> ...
> The Navion condensing unit is an impressive water heater, but for the price difference between it and a regular water heater you could do a DIY solar water heating system and have nearly free solar heated water and still have money left over....
> 
> Gary


That means my previous statement and my calculations are correct, while your previous statement and your calculations are false. 

And please stop to misinform people at least here.
Once again, my tread is very specific: &#8220;When does purchasing a solar water heater make sense?&#8221; ( &#8220;Solar water heaters versus modern conventional water heaters&#8221;.)
There are many treads for your DIY projects, but not here&#8230;
The efficiency of almost all DIY solar systems is close to ZERO during cloudy days for the cold climate!!!

My tread is for the homeowners who would like to spend money wisely.

Navien NR-180 Tankless Water Heater, 150K BTU
$1,098 and Up (from BuyPlumbing.net )
Navien Condensing Tankless Water Heater, Natural Gas With Navien Condensing 98 percent, you get the best of both worlds: the Best Value and "Ultra Condensing Efficiency", which offers substantial savings and contributes to a green-friendly environment. 0.96 energy factor 17000 - 199000 BTU/hr Flow rates - At 35 Degree Fahrenheit Rise : 10 GPM, At 45 Degree Fahrenheit 
Rise : 7.7 GPM, At 77 Degree Fahrenheit Rise : 3.8 GPM Easy installation and PVC venting Includes NR-10DU remote control
http://www.buyplumbing.net/?pg=pd&_i=NR180
http://www.buyplumbing.net/index.html?pg=pd&_i=NR210
http://www.buyplumbing.net/index.html?pg=pd&_i=NP240

Qualifies For: Up to $500 Federal Tax Credit. And Up to $300 EnergyStar rebate.

Boris Romanov


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## mightybooboo (Feb 10, 2004)

Boris,take your attacks elsewhere,for sure you arent welcome in my home,on to IGNORE you go.

Ahhhh,MUCH better.


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## artificer (Feb 26, 2007)

So, Borris, your thread title should have been "If you don't have a water heater, have lots of money, and are interested in solar, when does purchasing a solar water heater make sense?" I guess thats just too long of a title.

If you already have a working water heater, go somewhere else, since this thread doesn't apply to you, unless you want to toss it out, and buy a new/expensive heater.

If you think its better to spend $1000 on replacement heater instead of building something to dramatically decrease your fuel cost, this thread isn't for you.

If you think a DIY system is going to work much worse than a commercial system, just because you can't make a good solar heater, this thread isn't for you.

How long has the Navien been around? How many are in homes already? Whats the reliability of the units? A 5 year warranty doesn't give me a good feeling of dependability. Who can service these units? Are they in this area? How much is it going to cost? 

Boris, I have a problem with your whole argument. In your "proof", you average the sunny/cloudy day heat numbers. Is this for your area? You have cloudy days half the time during winter? Does eveyone reading this thread have the same weather conditions? You argue that Navien unit has 98% efficiency, since they say thats the performance they list. You then argue that the listed performace of a solar collector is in error, since your calculations do not support their statements. Why is one companys statements correct, and the other isn't? 

Gary stated the conditions for the data he measured. This is for his location, on those days. The numbers are correct. If you insist that your very narrow possible scenario (new water heater and very expensive solar collectors) is the only possible way to determine if solar heating makes sense, then your thread is probably not applicable to the people on this forum.

Add in your whole _The efficiency of almost all DIY solar systems is close to ZERO during cloudy days for the cold climate!!!
_ is silly. Are you saying that commercial solar collectors are better in cloudy conditions? Are you saying that most people don't know that if the sun isn't out, you will not get solar heating?

I'm still trying to figure out if you're for or against solar water heating. Personally, I plan on building something like Gary's system for our off-grid farm.

Michael


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## Ky-Jeeper (Sep 5, 2010)

Solar Gary, thank you for all that you do.


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## Kevingr (Mar 10, 2006)

Boris is going strictly off of marketing information and not real life like Gary is. When I first read this post, without looking at Boris's site, I thought he was a selling something.

DIY and Commercial products bring different things to the table. Many people won't touch a DIY product/project and others would never touch a commercially made product. It all depends on how much money and what kind of skills a person has. But, to tell someone that has actually done it, and has had real savings, that there information is false is ridiculus. Could a commercial product make the savings more than the DIY project? Maybe, but at a much higher cost.

I'm with Gary when he questions the cost of commercially available products. I don't understand why they are so costly, and I don't know how people can make them be economically viable in the short term. Even the high efficient condensing units as opposed to a standard water heater (a "water heater" isn't a "condensing unit" and a "condensing unit" isn't a "water heater") price difference is ridiculus. It takes many years just to get a payback on the condensing unit.


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## Boris (Nov 18, 2010)

Kevingr said:


> ... But, to tell someone that has actually done it, and has had real savings, that there information is false is ridiculus...


Kevingr,

Please read my post #14 more carefully,
My calculation is based on the efficiency of modern gas water heaters. 
So, Gary&#8217;s 60% (from his Post#2) versus modern 98% is a nonsense!
And his price range for the modern water heaters is false too.
Therefore I asked him to stop misinforming people.

In my opinion, there is no better alternative (cost/efficiency) to the modern Condensing Tankless water heaters for the homeowners who have access to the natural gas and who live in cold climate.
But you to have to shop around to find a best price for a water heater similar to the Navien. And you have to apply for the Federal Tax credit and for the Energy Star rebate.

I hope I will post my calculation of payback period for this scenario next week. 

Boris Romanov


P.S.
Just in case:
PSE&G Offers Navien Tankless Water Heaters to its New Jersey Customers
http://www.pseg.com/home/customer_service/worry_free/replacements/waterheater/tankless/navien.jsp


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## Boris (Nov 18, 2010)

&#8220;The Heat Pump Water Heater is an integrated system that utilizes heat pump technology to provide a more efficient way to heat water with electricity. Similar to your home air conditioner in reverse, the Heat Pump Water Heater extracts heat from the surrounding air and transfers the heat to the water in the tank. This is a very efficient means of heating water, and yields a by-product of cooler, dehumidified air. More storage capacity allows the water heater to operate in the most efficient mode and generate greater savings compared to smaller capacity heat pump models.

2.3 EF: Saves the home owner significant money. Standard electric water heaters are .87 to .95 EF. Less than half the cost to operate compared to a standard electric model (average of $540 versus $201 for the Heat Pump Water Heater).
* Pay back in 3 years, or quicker with state and local rebates.&#8221;*
From: http://www.whirlpoolwaterheaters.com/products/6thsense/heatpump.aspx?category=whp-w789


"Rheem EcoSense 50 gal. Hybrid Electric Water Heater with Heat Pump technology - $1,200.00
&#8220;*The investment return period is less than 1.5 years with application of federal tax credit and other state/utility rebates.*&#8221; By GE

Condensing gas water heaters are most efficient and reliable among gas water heaters. 
Navien has created high capacity condensing tankless water heater models that have an efficiency of 98%. 
Rheem, Rinnai/GE, Bosch, Noritz and Takagi make condensing water heaters that are not too far behind. 

Some brands already have a very good reputation.
For example, &#8220;Rinnai is the 2010 Builders' Brand Leader as chosen by home builders in Builder Magazine. The Alliance to Save Energy awarded Rinnai their prestigious Super Nova Star Award for energy efficiency and Bestcovery.com chose Rinnai as The Best Tankless Whole-House Water Heater.&#8221;
&#8220;*Energy savings with a tankless water heater typically result in a payback within just a few years for a family of four, making a tankless water heater a better long-term investment.*
http://www.rinnai.us/tankless-water-heater/how-much-is-tankless/

To calculate the potential reimbursement period in years you have to divide the cost of your installed heater (after all credits and rebates) by the amount of annual savings. 
For example, roughly the investment return period is about 4 years ($1000 / $250 = 4) years) for natural gas or less that 3 years ($1000 / 400 = 2.5) for LP.
With the &#8220;Tankless Water Heater Energy Savings Calculator&#8221;
you can calculate your individual Savings amount:
http://www.rinnai.us/tankless-water-heater-energy-savings-calculator/

Also I&#8217;ve added more pictures and comments here:
http://www.beebehavior.com/solar_water_heaters.php

Boris Romanov


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## Fat Charlie (Sep 9, 2010)

When does buying a solar hot water system make sense? Not often, when the sun is free, there are many ways to collect its heat and you can build large insulated tanks to hold that heat. When does depending entirely on massive infrastructure to heat your house make sense? To me, never.


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## poorboy (Apr 15, 2006)

330gal of propane supply's hot water and runs the cook stove a whole year!
I don't think it takes that much actually more like 300 gal..


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## Boris (Nov 18, 2010)

Fat Charlie said:


> When does buying a solar hot water system make sense? ... To me, never.


Iâm not so pessimistic.
Recently, the Silicon Solar has become much more reasonable with their new Combi Kitâs pricing.

*HelioMaxx Combi Solar Hot Water and Heating Kits*
"Designed to handle more than 50% of domestic hot water load & approximately 30% space heating.
HelioMaxx Combi kits are designed to make combination domestic hot water and heating system installation a snap. They are one of the most complete kits available on the market today and are available for a wide range of home sizes and climates. The kits utilize evacuate tubes for superior performance and high-quality commercial grade solar tanks for heat storage during the winter months. These are some of the most comprehensive kits on the market and include almost everything you need for turnkey installation.â SunMaxxSolar

In my new thread I will show the payback periods for such systems.

Boris Romanov


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## Ky-Jeeper (Sep 5, 2010)

You know this is more of an DIY forum than a "have someone install it forum." Just my opinion.


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## woodsy (Oct 13, 2008)

> In my new thread I will show the payback periods for such systems.
> 
> Boris Romanov


Maybe you should ask if anyone is interested first, before you waste your valuable time.

BTW folks, my 1K DIY solar hot water system made with plans from Build it Solar has worked flawlessly and will be paid for after only 2/ 1/2 years of operation. 


Don't let the kit vendors tell you that a DIY solar hot water system is not worth the effort and using the sun requires no petroleum products..


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## Fat Charlie (Sep 9, 2010)

Ky-Jeeper said:


> You know this is more of an DIY forum than a "have someone install it forum." Just my opinion.


Ditto. That's why I can't see buying one.


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## frank (Dec 16, 2008)

I built 3 different solar heaters from Gary's inspiration. 2 in Florida, (that work very, very well) and one in Alabama with the tank in-ground(clay). It works very well also. All those numbers...probably could've built a system that works in the time it took to do the research! And it'll work whether the propane truck makes it or not (on sunny days) lol. The sun is our friend...


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