[clug] Exercise and pay the bills!

steve jenkin sjenkin at canb.auug.org.au
Sun Feb 8 04:12:01 GMT 2009

Simon Fowler wrote on 8/2/09 1:02 PM:

> What are the prices and rebates on solar panel systems? I've had a
> quick look into them (out of curiosity more than anything, since
> we're renting at the moment), but all I've seen are quite broad
> numbers.
> Also, what are the numbers on paying for itself, and the expected
> lifespan?
> Simon

Apologies in advance for repeating stuff already posted.

ACTEW has a page, minus the new gross production tariffs:

The FedGov offers $8/W rebate to households with <$100,000 taxable
income (min 450W, max rebate @ 1KW)

With the 'stimulus package' news reports are that the income limit will
go and the rebate drop.

There is a $1,600 grant for uninsulated homes starting 1-Jul-09 (part of
stim-pkg) but a 3-Feb eligibility date:

There is a Solar Hot Water rebate of $1,600 for home-owners who haven't
claimed the insulation grant:

Wikipedia has an intro article:

As for costs and durability. this random company (no relationship to me,
never used them) has pricing (assume includes rebate):

1Kw Home Solar Power System: $4,990 - $5,490 inc. GST
2Kw Home Solar Power System: $14,990 - $15,490 inc. GST

"Supply and installation of six/twelve (6/12) Poly-Crystalline 170
Watt Solar Panels, TUV Certified featuring Suntech PV Cells and 25 Year
Performance Warranty"

Implies to me a 25 year 'useful life' - PV output does decline over
time. What's the end-of-life derating? Didn't see.

Solar PV cells do derate with operational temp. This link says "-0.5%
per degree C" (above 25C). With the hot weather we're having, I'm
/guessing/ 70-90C op temps, so around 30% derating..

Fixed systems need to be properly angled (tilt and orientation) - you
can significantly derate total output just lying them on your roof.

"For best year-round performance a fixed PV array would be mounted
facing true north (± 5°) at an inclination equal to the latitude angle".

There's another 'gotcha' - derating from leaves and shade.

Panels are made up of columns of cells in series to get the output
voltage up to something reasonable (15-20V for 12V nominal), then these
columns are wired in parallel.

Any shading within a column will reduce it's voltage below the system
level and it contributes nothing. These days diodes prevent power being
pushed back into the column & destroying cells.

For off-grid use, I know from the small system I installed in 1989 that
batteries/storage are the biggest problem. Lead-acid have a finite life
- even on 'float' (as those of you with small UPS's know). And
"deep-cycling" - what you really want if off-grid - should be limited to
50% of capacity and requires special (== costly) cells.

Steve Jenkin, Info Tech, Systems and Design Specialist.
0412 786 915 (+61 412 786 915)
PO Box 48, Kippax ACT 2615, AUSTRALIA

sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin

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