Brock,

Help me out with wattage per square footage. I think in terms of commercial applications, but residential limitations may restrict the ability to get ample wattage on the roof as well. So as much as wattage per hour is a concern, I think wattage per square foot is also an issue for me. I have the ability, in El Paso, to do a lot of flat roof installations visiually protected by parapets, so I can max out square footage in ways those limited to pitched roofs cannot and not worry about unsightly PV panels being seen from the street.

A lot of the more "decorative" panels, the ones that look like shingles have a lower wattage per square foot, they also cost the most, typically about $8-10 a watt. Then you have the panels that looks dark blue or purple in color and look like smeared out crystals, they are more efficient per foot and cost the least, right now in the $3-5 range. And finally you have the panels that have the purple/blue circles on them, cut silicon wafers, they will get you the most wattage per square foot, but also cost a bit more, in the $4-6 range. The last two come in all sizes and are typically mounted in an aluminum frame. Both of these last two typically last 25 years or are guaranteed to 80% of their rating after 25 years. Both have been beating that performance wise. The thin film or flexible or decorative panels are usually rated for 10 years and don't hold up as well, those are typically the ones you see at places like Harbor Freight or on eBay a lot.

Thanks Brock, that helps a lot. Do you have any ballpark figures for what a 625 watt panel might actually generate over the couse of a sunny summer day in Green Bay and over the course of a typical year taking into account weather. I'm guessing something on the order of 3.5 to 4.5 kwh over the course of a sunny Green Bay Summer day and maybe 650 to 800 kwh per year but am probably way off.

My max this summer has been 3.8 kw/day. With our last system, 4 KC 125's or 500w I typically saw 2.6-3.0 in summer in winter on a good sunny day I saw 1 and ranged everywhere between. For the previous two years it made just about 500kw each year. I think this location has a better southern exposure; our last one got no sun until about 10am so I had them tilted south west. Now I am pretty much straight south.

But your guess is probably close, conservatively I would say the wattage of the array in kw for the year, hopefully more, but I haven’t seen less yet.

I hadn't thought about it in year terms in a while, since we have time of use that off set $.21 / kw power so I generated a whopping $210 in the last two years, at that rate 10 years would be just about on, for the solar panels alone.

Then again my intention was grid backup, not generation. It was either spend the money on a battery backup with solar or a nice whole house genset. The genset would never payback and is noisy, consumes fuel that I would have to store (and rotate) and isn't as automatic or instantaneous.

That info is very helpful. We have low utility rates here (4.6 cents per kwh) so even $1/watt panels don't make sense yet. But our electric rates will no doubt rise to the point where $1/watt panels do make sense. I hope that's a long time from now but I know that it isn't.

I wonder how soon these panels could be available for home use? Bigger fish to fry for them right now but a more economical panel for residential use would be nice. We hope to start contruction on a house in 2011, maybe sooner if the market rebounds, and I'd love to have a grid-tie system in place at a cost that pays back sooner than 20-30 years.

Here's to hoping!

Straight grid tie systems (no battery backup) typically have paybacks of about 10 years, less if your further south and more if your further north.

So your payback in Antarctica should be almost instantaneous, cant get any more south than that.

wow, hi again everyone, i've been away from this forum for a while as work has been ramping up but I'm so glad to see how active and informative this thread has become!

Will any of you on the west coast be attending the West Coast Green event?

Dang you almost made me shoot Pepsi out of my nose!  LOL 

I stand corrected.  The closer you are to the equator the quicker the payback  ;)

Oddly enough, he's actually right. Antartica during it's summer would run continuously and has a thinner than normal Ozone (the magnetic poles make the spots more vulnerable to atmospheric changes of the last century). You probably could get pretty good figures out of it, but what would you send it to? Not many penguins seem interest in buying air conditioners and refrigerators.

I think the mark up thought is a misunderstanding. The $1 / watt figure includes markups for making a profit, not simply the cost of materials. Even if retailer markup was then 100%, you're still looking at $2 / watt, which makes a very fast break even point.

AWESOME!!!!!

Really?  Which oil company?

Which Oil Company?

 Here is a hint:  Google NiMH battery Chevron

Here is a great link for Pricing on solar panels - the lowest cost last I checked was $1.20 - but $2/w was more realistic.

http://www.ecobusinesslinks.com/solar_panels.htm

Posted By Alton on 17 Feb 2009 07:10 AM

Which Oil Company?

 Here is a hint:  Google NiMH battery Chevron

Ok I did. And the link says that GM bought the patents in 1994. That means the patents have expired already or will expire in less than a year. So now anyone can churn out and sell these miracle batteries to anyone and any car company that wants to make money. So you should see tens of thousands of cars on the market within the next couple years equiped with these batteries and the gas crisis will be over. Of course if the technology didn't actually work well enough at the right cost then you won't..........and I'm guessing you won't.