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Posted by Eeyore on October 29, 2008, 2:38 am
 


daestrom wrote:


Could be so. Pretty much a waste of time in the UK though. Consider excessive
draughts first and make sure your loft/attic insulation is 10-12" thick.

I had my ~ 2mm thin glass Victorian windows rebuilt with 6 mm laminatated glass.
Cuts noise down a lot too. It's quite difficult to make sliding sash double
glazed windows btw or at least insanely expensive.

Graham


Posted by Ron Rosenfeld on October 27, 2008, 1:28 am
 
wrote:


As I wrote, I think the cost quoted is reasonable when someone else is
providing all the material and doing all the labor.

However, your monthly cost of $09 is irrelevant in figuring the cost
savings.

The important value, in terms of what you are paying, is your cost **per
kWh**, and your cost of money.  The amount of kWh you consume each month is
also important if you should be consuming less than you produce.

In the Sacramento area, according to the PVWATTS calculator at
http://rredc.nrel.gov/solar/codes_algs/PVWATTS/version1/US/California/Sacramento.html

will produce about 10,800 kWh of AC per year.  So you will avoid paying
your supplier for that amount of electricity.

In order to save $30/month on your bill, your new rate would have to be
about $.365 per kWh, during the daylight hours.  That is a pretty high
rate, but some of the published TOU rates for PG&E are that high or higher.
You'll have to look at your electric bill more closely to see if that is
correct.

I don't understand how your installer computes a payback of 6 years.  If
you will be saving $30/month, and you've paid $0,154 for your system,
even if you assume the time cost of money is zero, that still comes out to
30154/330/12 = 7.6 years.

If you assume cost of money to be 5%, (and money has a cost even if you
self-finance, as you could have it invested in bonds or US Treasuries or
something reasonable secure), your payback period will be 9.6 years.

Of course, maybe he is inflating that $30 per month to account for future,
assumed electric rate increases.  Only you can assess the reasonableness of
that if he is doing so.

If he is not including the cost of money in his calculation of pay-back
time, then he is not providing you with proper data, in my opinion.
--ron

Posted by Eeyore on October 27, 2008, 8:46 am
 

Ron Rosenfeld wrote:


He uses a *special* computer called a 'salesman' !

Graham


Posted by Ron Rosenfeld on October 27, 2008, 11:55 am
 On Mon, 27 Oct 2008 08:46:04 +0000, Eeyore



Posted by busdweller on November 2, 2008, 12:57 pm
 wrote:

My home should get a total payback in about 7 or 8 years after rebates
and tax brakes. Make no mistake about it. When considering a PV
investment you must think long term. Amarica is a great place but we
all seem to want it all right now. My moma used to tell me, She'd say
Den, "Good things come in time" My Moma never lie's, at least I don't
think she does }:o)

Peace along the way
Dennis the bus dweller N.Y.

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