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solahart solar hot water system-australia-doesn't seem to save much money.....

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Posted by laz on August 18, 2004, 11:01 am
We bought a solahart black chrome 12  BCXII system about 2  1/2 years ago
and it doesn't seem to have reduced our electricity bills by very much
it has 2 black solar thermal panels, and a 300L tank
with an thermostat controlled electric booster
(we can also enable or disable the booster,ie disable booster means it can't
turn on the booster,
enable booster, means it will turn on or off depending on the water temp in
the tank)

in winter, with the booster thermostat on, our bills are only about
$0-30/bill lower than before
(with 1 bill every 2 months)
in winter with the booster off, we save more, but run out off hot water at
times....so no good

in summer with the booster on, the electricity savings are not that
(eg saving are about $0/2 month bill, and the savings with the booster off
are  $00/2 month bill)

have others had better savings ?

we have between 3-5 people in the house-varies
and it's a large house.


Posted by Gary on August 18, 2004, 2:05 pm
laz wrote:

Hi Laz,

You might try downloading and running the SolaHart SCF software from
the SolaHart website.  Based on which unit you have, where you live,
the orientation of the collectors, and several other factors the
software will tell you what SolaHart thinks you should be saving.  The
software is very easy to use, and appears to be well done.

By varying the inputs, you might also get some idea what might be


Posted by Bert Menkveld on August 18, 2004, 7:30 pm
 Hello laz,

Well, you haven't told us where you live, how big the panels are, and what
the price of your electricity is.  However, saving $00 off your bill every
2 months during the summer sounds like very good savings to me.

If you can supply the above mentioned details, you'll likely get some more
useful responses.



Bert Menkveld

Posted by laz on August 19, 2004, 2:40 pm

"Bert Menkveld" <bertATreentronicsDOTcom> wrote in message

i have this model
i have a 300L tank with two panels
(it uses heat exchanger with two systems-one liquid going through the two
and using this to heat the water)
i have the 302BCXII

electricity is about 14c (AUD) /kwhr
i live in perth, western australia

the system cost about $000 AUD


Posted by Bert Menkveld on August 27, 2004, 1:13 pm
 Well, let's work through your numbers.  You're saving $00 over two months
of summer weather, with electricity priced at $.14/kWh.  That means your
solar energy contribution over those two months is:

E = $00 / $.14/kWh = 714kWh.

Assuming 60 days, that's about 12kWh per day.

The Solahart web site doesn't seem to provide the size of each collector,
but it looks like it might be about 2 m^2 (2 square metres) per collector.
Since your system has two collectors, let's use a total collector area of 4
m^2.  Dividing energy collected by collector area:

12kWh per day / 4m^2 = 3kWh / m^2 per day

Assuming a system efficiency of 50% (a reasonable number for a solar hot
water system), your average insolation (amount of sunlight falling on the
panels) would be:

3 / 50% = 6kWh / m^2 per day

That's roughly the equivalent of 6 hours of full sunlight shining directly
on the panel (ie. at right angles to the surface of the panel).  Since the
sun doesn't normally stay still in the sky, the panels actually only receive
a fraction of the maximum possible energy, depending on the angle of the
sun's rays with respect to the panel.

I guess you have lots of sun in Australia (I live in not-so-sunny Ontario,
Canada), but the equivalent of 6 hours of full sun per day sounds pretty
good.  If you want more than that, you need more collector area.

Of course, you can also approach this cost issue from the demand side.  My
family of 5 uses substantially less than 12kWh per day of hot water energy.
You may be able to reduce your electricity bill by reducing your hot water
consumption.  Also, you might consider an extra insulation "blanket" around
your hot water tank(s) to reduce heat losses from the storage tank(s).


Bert Menkveld


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