[aprssig] Solar Payback

Bob Bruninga bruninga at usna.edu
Mon May 23 12:25:24 EDT 2011

We need to move this to SolarDIY at yahoogroups.com

> I have tried playing with that PV Watts website.
> But for my location with a 1kW setup it says I will 
> only make about $100 worth of energy per year.

Yep, I just confirmed only about $95 in Maryland..  BUT.. PVwatts uses a
2004 data base for state rates.  When I use the present 15 cents for my area
I get $187 per year.  Remember, this INCLUDES the "10 cent" nominal rate
from my utility PLUS the 5 cents of "distribution" charges per KWH.

> That means it would take about 20 years 
> for a 1kW grid tie to pay for itself.  
> Not very economical.

Ah ha!  You are overlooking many things (that I also overlooked... and that
is why I am trying to tell everyone to get rid of old ideas and start FRESH
with the new grid-tie economics)...

Here goes.  1) Do not be mislead in using the "price to compare" that the
utilities are quoting these days.  That leaves out the distribution charges
that also apply to every KWH used.

DIY Cost is $2000 for 1 kW of panels (4) at $2/watt
DIY Cost of grid-tie inverters is about $300 (two 500W models on Ebay)
Add $100 for misc
Total is about $2400.  
Less 50% in credits and rebates. -$1200
Total NET cost is $1200

You get $300/kw SREC payments per year    + $300/yr
You get the $187 per year in electricity  + $187/Yr
Total per year payback (first few years)  + $487/yr

So the system will pay for itself in under 3 years... Far from the 20 years
we all thought a few years ago.  But the above is unrealistic, because it
left out the Master Electrician to make it legal!

Also do not bank on the SREC payments for long, because those are INCENTIVE
payments only.  And with everyone jumping into solar as fast as they can be
built, you can be sure those payments will decay to zero quickly.  A guy at
Dayton said he is getting $600 per KW in New Jersey this year!!!  In
Maryland it is $300...  But SREC's are political money...  Don't bank on it.
At least you can count on $187 per year forever (that will only go up as
rates go up)..

And you are getting $187 per year for the rest of your life.  For a $1200
initial investment, that is like getting 15% interest on your investment..
(minus the oldest daughter you had to sacrifice to the Master

CAVEAT EMPTOR:  HOWEVER... The above prices are based on a small 1kW DIY
system.  Overhead and miscellaneous costs would make such a small system
impractical at contractor rates.  You would never find a contractor to do
such a small job for anywhere near that price.  But, as the system gets
larger, the overall amortized cost for the contractor gets smaller.

I'm going to start a thread on the SolarDIY group subject "Small Solar
Estimates"? Because the way I would do my system if I was starting all over
is :

1) Get a contactor to do a small system.
2) It would be installed with all the Building Permits, licenses and
grid-tie agreements.
3) See how it goes.
4) Add UL approved solar panels and Approved grid-tie inverters as the
system grows.

Bob, Wb4APR

-----Original Message----- 
From: Bob Bruninga
Sent: Monday, May 23, 2011 10:02 AM
To: ve3nec at sympatico.ca ; 'TAPR APRS Mailing List'
Subject: Re: [aprssig] TAPR Dayton Solar Talk

> I'd love to try... cells on my roof.. or preheat... hot water...
> (Is there another list somewhere where we should be posting this ?)

Yes, SolarDIY at yahoogroups.com for Ham radio solar ideas...

> is there an electrical "one way" valve for the electricity?

Yes, all grid-tie systems have that fundamentl characteristic.  They can
only push current against an existing waveform.  If the 60 Hz waveform goes
away, they shut down in a few milliseconds.

> How well P.V. cells would work in S. Ontario
> is anybody's guess. Anyone with experience ?

That is VERY EASY to answer and everyone should do it.  Just google for
PVwatts, the on-line solar power calculator.  It takes only a few seconds to
get a calculation for ANY size array, facing any direction ant any angle at
any location.  AND the calculations includes a 10 year weather model for
exactly your area.  It is the industry standard and is used by EVERYONE...
and it is so much fun to play with ideas and see the results.

Remember, the only thing that matters with solar grid-tie is the total
annual production.


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