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Commercial Solar Water Heaters ? - Page 2

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Posted by Rob Dekker on September 1, 2005, 11:19 pm

Having lived both in Northern Europe and in the US for 20 years each,
I have some ideas about that. There are many, many factors that play a role,
but the most important ones I think are the low cost of fossil fuel
(low taxation of energy) in the US, and a business attitude towards solving
recognized problems, rather than the more longer-term visions and of Europeans.

One thing that is important for this subject is that in the US, if there is
a business opportunity, someone will jump on it. Usually big-time.

So, where do you buy this ? At the local do-it-yourself home centers, or
at specialty stores ? And how much does a typical collector cost (per m^2) ?
How many choices do you have (are there many companies building these panels ?)

Does the German covernment issue rebates for solar systems to end-users ?
Or do they subsidize the manufacturers directly ?
How much (as a %) does the government subsidize solar heating systems ?

Isn't this just a good standard water heater ? (I think they are called 'boiler'
in Europe).
What does the tank use as backup ? Gas-burner ? oil burner ? or electric heater
element ?

Do you need a building permit before you can install your system on the roof ?
Does an inspector need to sign-off on the installation ?

10-15 years for return on investment is probably too long for US customers.

Most Americans don't live in the same house for more than 7 years, and
real-estate assessors do not yet recognize any value for a solar system on the
There is much more value in adding a bathroom (that's why US homes have
so many bathrooms..:o) or an updated kitchen, or nice landscaping.

How many homes in Germany use solar water-heating ?
In the face of this long investment period, it should not be that many...
This might the difference in consumer attitude that I described above.

Posted by Christian Kaiser on September 2, 2005, 10:19 am

Special stores and/or internet, usually around 140 EUR/m^2 or more. We get
subventioned by about EUR105/m^2, though, so collector area is very cheap
here. There are many companies building collectors, but I don't know how
often they are just rebranded ones. Austria is very experienced in
collectors, they offer several companies that exist longer than 10 years,
which is a good thing to know. ;-) They guarantee a life-time of 10 years,
some more.

I bought Austrian ones, at 360EUR for 2.6 m^2, they are "landscape"
oriented, a little bit more expensive than the "portrait" ones.

Yes, by gross collector area. By the above amount (changed recently from 110
to 105 EUR). As I have 11 m^2, it was (at 110 EUR/m^2) about 1210 EUR! That
is, if you have collectors of a certain quality (which they of course all
fulfill), that need to be able to get a minimum of 525 W by each m^2.

Well it is a tank that has two heat exchangers. In the tank there's water
from the oil heating, so not exchanged (thus no problem with lime.

The lower heat exchange is used for heating by the solar system, the upper
one to heat the water for the household.

For smaller systems, the tank is filled with the water you use, and the
upper heat exchange is used for the backup heating.

The heating itself (oil in my case, but could be anything that gets more
than 40 C into the tank) heats up the upper 30% or so of the tank, if

There are a lot of different tank systems, with "heat level" separation and
such, different forms of heat exchangers, ... you choose :) - they all try
to minimize convection.

Depends. Usually not, but might be for historic city centers that it is not
allowed to install one as it would destroy the nice roofs.

Actually I installed it at the front of the house, just on the wall. Best to
check with the local authorities whether the area the house resides has some
limitations. Usually not.

No. To get the money from the government, you have to sign that it works,
that's all, and to agree to let them check if needed.

Unfortunately, yes. Well look at the oil price, it becomes less time to ROI

I don't know numbers, but they are not very rarely to be seen.

For Austria, a study claims that there had been 1.7 million m^2 in 1997
(thus this country is leader!), which is about 4% of the homes. They expect
4 million m^2 in 2010.

Planned number for the whole European Union is 100 million m^2 up to 2010
(but I don't know if they succeed)! See
(in German).


Posted by Rob Dekker on September 7, 2005, 12:07 am
 Thank you Christian, for all this good info.

After some more (web) checking, it seems that commercial collectors are not more
here in the US than they are in Germany. $00 - $00 / m^2.

There are a couple of things changing here too :

  - rebates for solar energy systems starting to be a bit more common (and
hopefully will hold)
  - increasing natural gas prices (not to mention increasing electric prices for
those dumb enough to buy electric water heaters)
  - long-term financing for consumer products is very popular here, and could
work well for solar equipment

Now all we need is more businesses that jump onto this opportunity..

But to show you what we are up against (info from my own gas/electric bill) :
The base rate for (small) residential natural gas, here in California is about
$ / therm.

$ / therm :
1 therm == 100,000 BTU == 100 ft^3 == 2830 liter == 2.83 m^3
So nat gas cost $.35 / m^3   (28 EURct / m^3).

Electric :  $.11/kWh.

And California is one of the most expensive states.
Most other people probably pay only $.09/kWh or so.
Many 'bigger' users are paying (much) lower rates.


Posted by Christian Kaiser on September 7, 2005, 7:13 pm
 Sorry, the price here is 300-400 EUR for my collector, which has 2.6 m^2. I
wrote "around 140 EUR/m^2", so the US is still very expensive.

I know that all these systems are not saving very much - but ecology is also
an aim! If one has economy in mind, it might not be worth it, especially in
the US.

Petrol is up to 1.30 EUR/liter here, which is about 5 EUR/gallon. Oil for
the heating is about 70 Cts/liter. I don't know about gas - but as 1 m^3 has
about the same energy as 1 liter of oil, I would expect the same, more than
2 times than the US.

One good thing to say about the New Orleans oil shock: it seems that more
and more people think twice before using the car, and alternative energies
become more popular...


Posted by Paul on September 8, 2005, 3:39 am

  They just announced on the network news that the price for natural gas
for home heating in the U.S. will be up as much as 71% this winter and
the price of heating  oil will be up about 30%.
Maybe it is time for that solar thermal space heating...

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