My solar power experiences
Designing a 10 kW solar power system that was much larger than would
fit on my available roof space at Clare in Mid North South Australia was
not a simple matter.
I've written this page to record what I did and in the hope that it might
help other people with their solar power systems.
(I searched the net and didn't find any record of systems similar to the
sort of thing that I needed.)
My aim was to put some money into a good financial investment and, at the
same time, do a little bit to combat climate change.
The rules for getting a workable price for the electricity that one
feeds into the grid vary greatly from place-to-place and time-to-time,
this page deals with South Australia and Western Australia.
In the end we had to scale down from 10 kW to 1.5 kW because
the South Australian Government changed the rules on its incentive payment
for solar electricity.
This page created 2010/07/18, modified 2016/01/12
Contact: email firstname.lastname@example.org
On February 8th 2006 my wife and I were among the first in Crystal Brook to
put a solar
photovoltaic system on our home (photo at right;
we put the solar water heater up thirty years earlier).
In late June 2010, because of changed solar incentive offers from the
government, reduced prices of solar power systems,
and good electricity feed-in tariffs, we decided to set up a
much larger 10 kW system on a hobby farm at Clare.
The system was to be connected to the power grid (the design considerations
of a stand-alone system are quite different).
|Our other solar power system
A part of the solar setup on our
The PV is only a 1 kW system, not the main subject of this page.
The site available to us was fairly open with few tall trees (a dry climate
has some advantages) and sloped toward the north at a useful 5°.
The only suitably located building available to us had a roof much too small
for the required 54 or so panels (each around 0.8m × 1.6m).
We thought at first to place the panels on frames on the ground, but
were told that the frames would cost something like $10k and that we
might be better off to consider building a simple, large shed so that
the panels could go on the roof and the space inside would be useful
We had been thinking of building a pergola for summer shade near the
barbeque, so I started looking into designing a suitable pergola that
would also serve as a frame for the photovoltaic panels.
The problem here was that such a pergola would be very big and high as
well; it was difficult to imagine something that could be built for a
reasonable price and look acceptable.
Placing panels on a flat, or nearly flat, pergola roof at our latitude
(35° south) would require that they be tilted up on edge and arranged
in a number of rows (see box on the right).
If the rear rows were not to be significantly shaded by the front rows
early in the day, then there would have to be a large gap between the rows;
such a gap would make the pergola unacceptably long from north to south.
The other alternative was to tilt the pergola roof at an angle steep enough
to efficiently collect solar energy.
The best compromise angle seemed to be 20°, but even this lower than
optimal angle led to a roof that
sloped up to an unacceptable height (if the low end was 1.7m the high end
would be about 4m).
- The site must be open to the sunshine for the maximum possible
period of each day and throughout the year;
- With a large system, the front rows must shade the back rows as little
as possible, at all times of the day and year;
- The panels should be aligned as close as possible toward the north
and at the optimal tilt angle for the latitude (the optimal tilt for us
was about 30° at our 35° S latitude).
Panels that are fixed at low angles are likely to collect dirt and dust
and require cleaning, those at steeper angles are largely self-cleaning;
- The optimal angle for a stand-alone power system, in which one needs
the maximum amount of power in winter, when the sun is low in the sky,
is steeper, perhaps 50° for our latitude.
A lesser tilt is better for a grid-connected system because it increases
the amount of power being injected into the grid in summer when days are
long and the sun high overhead;
- They must be close to the point where the power can be fed into
the power service;
- It is important to keep the panels as cool as possible; in practice this
means maximising natural ventilation; see Temperature of panels.
What to do?
The best answer seemed to be to place half the panels on a
smaller pergola and the other half on and near the shack.
There was room for 21 on the roof and I could build a
veranda for the other
But politics were to intervene.
The power from solar panels is low voltage direct current (DC); it must
be converted to higher voltage alternating current (AC) before it can be
fed into a 'normal', 240V AC, power supply.
This is handled by a black box called an inverter.
Surprisingly, two five-kilowatt inverters (or three three-kilowatt
inverters) are cheaper than one ten kilowatt inverter.
This meant that it is quite economically viable to have two (or three)
more-or-less independent smaller solar power systems, rather than one large one.
In order to receive the full Federal Government incentive in Australia,
what they call
Solar Credits, the solar
power system must
be on premises which can be a house, church, school, or are associated with
your business activity (eg. a dairy in the case of a dairy farm, a shearing
shed in the case of a sheep grazing property).
I had to use the last alternative, my premises are used for the storage,
racking, bottling, labelling, and capping of olive oil from my 600-tree
olive orchard; the processes of bottling, labelling and capping were
accepted as processes that occurred on my premises involved in running the
Depending on where your place is, the local power grid may not be
capable of handling the output from a 10 kW 'small embedded generating
I had to contact ETSA (the organisation in SA that runs the poles and wires)
and apply to connect.
Some rural power supplies are not capable of handling as much as 10 kW of
power, especially SWER (single wire earth return) supplies that are a long
way from the main power lines.
I was fortunate in having installed a two-phase connection and being only
100m from a high-voltage three-phase power line, which itself was within
100m of two branch lines.
Solar photo voltaic panels produce less electricity as they get
the difference is very significant.
(I believe that thin film amorphous silicon panels suffer less from this
effect than do crystalline silicon panels.)
Therefore it is very important that panels attached to a roof should have
a goodly space under the panels and above the roof to allow the free flow of
cooling air between roof and panels.
My information suggests that at least 80mm should be provided, 150mm would
be even better.
My panels were installed on a free-standing frame, giving more ventilation
than would be achieved on a roof (see
I chose to use one of two accredited local solar power installers, either
Clewers (of Clare) or Luke O'Dea (with connections to Clare, Crystal Brook,
Clewers would use two CMS 5000 (5000W) inverters and 54 × 185W Enertech
monocrystalline panels having a total nominal capacity of 9990W.
O'Dea would use two Enerdrive GT 5.0 AU (5000W) inverters and
51 × 190W Phono panels having a total nominal capacity of 9690W.
The major hiccough,
referred to elsewhere, changed things, but eventually I went with Luke
(although I'm sure that Clewers would have done the job very well too).
One of the initial quotes included trenching, the other did not; but as
there was only one trench about 25m long involved I felt I could dig it
myself without much difficulty.
It was suggested by one of the installers that the brand of panel used
by the other was of inferior quality.
I could see no way of checking the truth of this, other than asking
that installer, who (as you would expect) held that the panel was of
I expected the whole thing, before the
major hiccough, including building the pergola,
to cost about $50k for 10 kW.
I use only about 2.5 kWh of electricity per day (about 1.3 kWh
during daylight hours).
The 10 kW solar power system should generate about 42 kWh per day,
of which about 41 kWh will go into the grid each day (about
15 000 kWh per year).
The government payment in SA was, at the time I was planning this,
44¢/kWh, electricity retailers pay an
about (depending on retailer) an additional 8¢/kWh.
Income should be near $8000/yr, paying back the cost of the system in
around 7 years and paying about 16% on the money invested.
("The best laid plans of mice and men aft gang aglee.")
It seems that everyone who is making any forecasts in Australia is
predicting steeply rising electricity prices.
This must happen for several reasons:
All of these changes will have to be paid for, and much of the cost will
finish up in the price we pay per kilowatt-hour for our electricity.
- The Australian power system is in dire need of upgrading, and the
upgrading will be very expensive;
- We have to change from fossil-fuelled to renewable power;
- We have to change the flat fee for power to a
varies with supply and demand;
The result of this should be to increase the value of existing solar
power systems in the future.
When figuring how much it is all going to cost you, you should not forget
that you will probably need a new electricity meter; ours cost us $652
(our daughter in WA only had to pay $250 for hers).
In the end my wife and I were not able to install our 10kW solar power
system, due to the
major hiccough discussed elsewhere.
Instead we installed a small (1.5 kW, about $3k after Fed.
handout) solar power system on our own place on 2011/01/18 and paid for a
larger (5.3kW, about $23k) system to be installed on our
daughter and son-in-law's house in Western Australia on 2011/01/25.
In its first full day of operation, the 26th, this installation generated
a promissing 40 kWh.
In return for paying for the WA system we will get half of the money that
our kids save on their power bills.
(I've estimated that from the present roughly $2100 annual total payment
for power they should go to a refund of something like $1500.)
The calculated annual return for us is around
$1800, or 8% on our investment, the kids should save another
$1800 in power bills.
Later we paid for a solar installation, I think it was about 3.4kW, on our
son and daughter-in-law's flat in Adelaide.
Before late August 2010 the South Australian Government payed 44¢/kWh
for solar power fed into the grid (a 'net payment' system).
Following that date they made themselves look good (superficially) by
increasing the payment to 54¢/kWh, but at the same time greatly reduced
the number of people who could qualify for this, and greatly reduced the
maximum size of the solar power system that would qualify.
When the government changed the rules
for people who want to receive the electricity feed-in tariff to
specifically exclude anyone hoping to make a profit and anyone who already
has a solar power system, no
matter how small, they made my proposed 10 kW system unviable.
A carbon tax
What our governments should be doing rather than fiddling with rebates and
payments to owners of solar power systems, is making the greenhouse polluting
pay for the damage they are doing
to the world, so that non-polluting sustainable generating systems
become economically viable in their own right.
As well as greatly reducing greenhouse gas production it would be much
simpler and lead to fewer distortions of the economic system.
Inquiries with the Dept. of The Premier confirmed that our system will not
So, instead of installing a 10 kW solar power system on my own place I'm
arranging to pay for a 5 kW solar power system on
my daughter's place in WA
and have a 1.5 kW system put on my own place.
We will not get the 54¢/kWh feed-in tariff for our little 1.5 kW
any more than we would for our originally proposed 10 kW system, but we
should still get about 8¢/kWh from the electricity retailer, and
feel that we are
doing a bit for the planet.
We were advised not to put anything as large as a 10 kW system up in WA
because of the perceived probability that the WA Government were intending
to change the rules similarly to SA.
In the end, even though I had no expectation of getting more than 8¢
per kilowatt-hour for the power I would be feeding into the electricity
system (because of the
Government's changing of the rules) I ordered a
1.5 kW system (8 × 190 Watt panels) from Luke O'Dea at a
cost, to us, of a bit less than $3000 (the
Federal Government's shonky solar
credits scheme paid $6200).
|Our solar panels at Elysium|
They provide shade to our north-facing wall and have excellent ventelation
We also had to pay $652 for the new (3 phase) electricity meter (a single
phase meter is cheaper, about $400).
Our daughter in WA had to pay only $250 for her new 3 phase solar meter.
I have asked ETSA why the difference, and written a letter to several
newspapers posing the same question.
The 1.5 kW system should generate about 2300 kWh per year.
This was a much smaller system than the 10 kW that my wife and I were
originally planning but at least it was an investment toward reducing our
greenhouse footprint and it was not a huge financial burden.
There were several reasons for placing the panels on the frame on the northern
side of our shack rather than on the roof.
The cost of the steel for the frame was about $500, and $80 for the
(dry-mix) concrete in the post holes.
- The roof had a slope of only 11°, not sufficient for optimal
solar power generation at our latitude; the frame gave a slope of
26° to the panels;
- The shade from the panels would keep the hot summer sun off our northern
passively keep our temperatures down;
- The panels would be able to get the maximum cooling ventilation,
minimising the operating temperature
and maximising their efficiency.
When the photo was taken (2011/01/21) everything but the inverter was in
place, the panels were installed on the 18th.
I had to wait until 2011/02/02 for the inverter to arrive and be installed;
the new meter (capable of measuring feed-in as well as consumption) was
installed the next day.
The installer's figures indicated that I should expect an average energy
generation of about 8.7kWh per day for February.
This was calculated for a tilt angle of 30°
and at Adelaide's latitude – 34.9°S.
The tilt angle of my panels is 25°, which
should very slightly increase the generation in February,
and my latitude is 33.8°S, which also gives a very slight advantage
compared to Adelaide.
Based on data recorded on 4th and 7th Feb. 2011, the power output of our
system fits the multiple linear equation
P = 0.0107 L - 4.71 t; where
P is power in Watts, L is light intensity in Lux, and t is panel temperature
measured by my infra-red thermometer in degrees above 23°C.
This roughly means that it generates 11 Watts for every thousand Lux, but
that this is reduced by 4.7 Watts for every degree C that the panels are above
The first full day of operation, 2011/02/03, the maximum power achieved was
about 1100W (Nominal power of our system was 1520W);
and 5.3kWh was generated.
The maximum ambient temperature was around 38°C and the panels got up to
around 65°C (measured from the back with an infra-red thermometer and
need for maximum
There was cloud cover for more than half of the day.
Three years of operation
In the first three years of operation the system produced:
The capacity factor is the power actually generated as a percentage of what
would be generated if the system operated at full label capacity 24 hours
a day and 365 days a year.
As one would expect, there is a linear relationship between light intensity
and power output; with an increase of about 11W for each thousand Lux.
The power output of silicon solar panels, especially crystalline panels
decreases with increasing temperature, and an analysis that I did on
2011/02/15 indicates that the output of our system decreases by 4.7 Watts
for each one degree increase in temperature.
By 2011/02/22 we were averaging 6.8kWh/day at the inverter, significantly
less than the installer's forecast (see box on the right).
The short-fall would probably be due to there being a lot of cloud cover
for the time of year.
The maximum power that I had recorded to then was 1326 Watts.
The graph on the right has the power (in Watts) generated by the
panels plotted agains the light intensity (in Lux).
As you would expect, in general, the brighter the light, the more power.
But the data do not fall exactly on the trend line.
The scattering is due to the variable temperature of the panels during
The light sensor is facing the same direction as the panels
This graph shows the same data as in the above graph, but with the
temperature factor mathematically removed;
the much closer match between data and trend line is conspicuous.
This strongly suggests that the predominant factors affecting the power
production from our solar panels is light intensitity followed by temperature.
This is roughly what the power output of our system would look like if the
panel temperature could be held to 23°C.
Early data from our solar power system at Clare are shown in the graph on
The blue points represent the power generation as recorded by the
inverter, the pink is the power that we have imported from the grid,
and the yellow is power that we have exported to the grid.
(Import is shown on our ETSA meter as item 03, export item 09.)
It is pleasing that we are exporting three or four times as much power
as we are importing; a good result considering we only have a 1.52kW
It was less pleasing that our system generated an average of 7.04kWh/day
in February; the installer's figures indicated 8.7 as the expected average for
(It generated 5.99kWh/day in March, against the stated 7.7.)
But there was probably more cloud in this February and March than
average, time will tell if it is as good as it should be.
Our average electricity consumption before installation of the solar
system was 2.24kWh/day.
As mentioned elsewhere, the solar power system that we had installed at
Clare was rated at 1520W and the one installed on our daughter's house
at Mandurah in WA was rated at 5280W.
Our unit has eight 190W mono-crystaline Phono panels, a 1.5kW SMA Sony
Boy inverter and was installed by O'Dea Electrical on 2011/02/02.
Our daughter's unit has 48 Kaneka 110W hybrid panels, a Xantrex GT5.0-AU
inverter and was installed by The Solar Shop, Mandurah on 2011/01/25.
To 2011/02/17 the greatest output I have recorded from our unit is 1326W,
that is, 87% of its rated capacity.
My son-in-law recorded an output of 5079W, 96% of the rated capacity of
the Mandurah system.
You'd have to say that, on this measure, the Solar Shop installation is at
present looking better than the O'Dea installation.
On 2006/02/08 my wife and I had six solar panels rated at a total of about
1kW installed on a shed at the back of our house.
At the time a rebate of $3600 was available from the Federal Government;
we had to pay about $12 000 ourselves.
(Compare this with the
new 1.5 kW system – the main subject
of this page – that cost us about $3000.)
|Solar power at Crystal Brook
|A part of two of the six panels on our place at Crystal Brook;
solar water heater in the background
|Electricity record at our home
The graph at the right shows a record of data from our electricity meter.
The blue line records that amount of electricty that we have taken from
the grid on our main circuit.
Our power consumption is greatest in summer due to two things: the
refrigerator and freezer have to work harder to maintain their set
temperatures, and we use a ducted evaporative air conditioner for cooling the
The pink line shows the amount that has come from the grid at off-peak
times for the electric booster of our solar water heater.
The yellow line shows that amount that has been fed into the grid from our
Power from the solar panels is fed into the grid only when its amount is
greater than the power that we are consuming in the house.
Effect of replacing the old freezer
We bought a new, more efficient, freezer on 2010/06/30; previous to this
we had a freezer that was more than 30 years old.
This significantly reduced our electricity consumption and increased the
amount our solar system was able to feed into the grid.
Our average power consumption on the main circuit for the two years before
this was 7.02 kWh/day and dropped to 4.38 kWh/day for the
period 2010/06/30 to 2011/01/16 (a decrease of 38%).
The average amount of power that we fed back into the grid in the two years
before the new freezer was 1.39 kWh/day and this increased to
1.96 kWh/day from 2010/06/30 to 2011/01/16 (an increase of 41%).
I have calculated that the $1100 new freezer will pay for itself in
four years due to the lower power consumption and the greater payments
for the power that we put into the grid.
On 2014/02/18 we had another 5.2kW (20 × 260W panels) installed on the
roof of the shack.
|New solar installation on our shack
|The top of the chimney needs some work!
The angle is not optimal, being only about 14°, although it does face
almost directly north.
This job was done by O'Dea again.
So now, my wife and I have paid for the installation of:
That's a total of about 16kW.
- 2006/02/08; 1kW of panels on our house at Crytal Brook
- 2011/01/24; About 5.3kW on our daughter's house in Mandurah
- 2011/02/02; 1.52kW on our shack at Clare
- 2011/06/29; About 3.4kW on our son's house in Adelaide
- 2014/02/18; Another 5.2kW on our shack at Clare
After the 5.2kW system had been in place for a full year (2014/02/18 to
2015/02/18) our power meter showed that we had exported 19 times as much
power from our shack as we had imported.
Over the year we had exported 10.2MWh.
That would have displaced fossil fuel electricity on the national power grid
and might have reduced greenhouse gas emissions by anything up to about ten
General solar power links
The Rainbow Power Company has a page on Solar Panel FAQs.
Wikipedia, Solar Power in Australia
Solar panel comparison links
Panels seem to be evaluated by giving them a PTC rating.
This is a contraction of "PVUSA TC", and appears to me to be quite
The rating we need
Buyers of solar power systems need to know how many Watt-hours they are
going to get for each dollar that they spend.
Obviously this will depend partly on their site.
Unfortunately rating systems such as the PTC one do not take price into
GoSolarCalifornia has a large page in which PTC ratings are given to
many makes and sizes of solar panels.
WholeSolarPower, a comparison between some 25 panel makes.