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<p>Hi Bob</p>
<p>There is nothing particularly detailed about my figures and there
is not much in the way of calculation! It is all simply an
extension of about fifteen years of work with grey water heat
exchangers. I have a standard Rheem electric storage heater with
its own exclusive kWh and water meters. The heat exchanger works
with a Maddalena heat meter which gives a daily output in kWh and
total water flow. The testing arrangement is not ideal but I do
know <u>exactly</u> what is going on!</p>
<p>I think it is a big mistake to try to plan for "just enough
panels" for your HWS. You are bound to get it wrong, and your wife
will be far from impressed.</p>
<p>The reason why I am looking at 3kW of panels is because that is
all that will fit in a single group on a north-facing roof. That's
real planning for you - architecture and environment, not
numbers. <br>
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<p>The 3kW means I only need about 1.5 hrs of peak power equivalent,
so I can be reasonably confident of getting that regularly,
particularly as the roof is pretty ideally pitched at 45 degrees.
It was actually built to take a (gasp!) solar thermal HWS, but
that never happened. For all that, I don't think the HWS is so
important since, if it was not on solar, it would be getting power
off-peak after 10pm. Far more important is the stuff that has
unavoidable daytime demand - the fridge, the stove, and winter
space heating. If you want to do some serious planning, that is
the place to look. All I have done there is confirm that the
energy label on the back of the fridge was correct on an annual
basis, and all that really meant was that getting a new one is not
such a high priority. Your power bills should tell you all you
need to know.</p>
<p>Nick Pyner</p>
<p>Dee Why Beach NSW<br>
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<div class="moz-cite-prefix">On 23/04/2016 11:48 PM, Jake jakaitis
wrote:<br>
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<p dir="ltr">
Helpful to understand how you arrived at these numbers?</p>
<p dir="ltr">I am interested in starting out my PV system with
just enough panels to power my new energy efficient whirlpool
hot water tank. T<br>
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