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RoofRay solar energy calculator

2008-08-14 15:43:48.585468+00 by Dan Lyke 7 comments

RoofRay - calculator to determine the solar potential of your roof. Our house is almost directly north-facing, so we've got the back side of our roof to play with (modulo various vents and pipes), but given our electric bills and general ability to conserve photovoltaics make zero sense for us. However, I am thinking about solar hot water pre-heating.

[ related topics: Real Estate Photovoltaics ]

comments in ascending chronological order (reverse):

#Comment Re: made: 2008-08-14 18:52:50.691852+00 by: ebradway

Wow! I hear a lot of arguments saying that Google Maps is useless for real GIS analysis. This is a great example of a lightweight analysis using Google as the basemap. It would be fun to take this thing apart to see how much geography they actually have imbeded in it (like latitude, average cloud cover, etc).

#Comment Re: made: 2008-08-14 19:30:11.236829+00 by: warkitty

I tried to get an analysis, but it kept timing out.


#Comment Re: made: 2008-08-14 20:09:14.92781+00 by: Dan Lyke

Warkitty, bummer, it was right fast for me.

Eric, they claim that their month-by-month estimate includes way more than you suggest:

This estimate is based off of your coordinates and regional characteristics such as the average weather cycle, cloud cover, surface albedo, and the orientation and area of your solar array.

Given that they adjust for seasonal energy costs, I can't imagine that they're not also looking at seasonal energy production. I'd have to get more specific with our bills, but with an off-the-cuff PG&E bill of $80/month, which is probably way high, especially since our summer bills nowadays seem to be closer to $20 and summer energy should cost me more, the pay-off was 17 years.

Which leads me to my main issue with photovoltaics right now: I've a rough idea that commercial manufacturers of silicon cells are looking at 5 years for manufacturing capitalization payoff, and there's a lot of uncertainty over technologies, my gut feel is that that payoff by 2025 will remain roughly constant for at least 10 years.

#Comment Re: made: 2008-08-14 20:55:09.109878+00 by: spc476

The top edge of our roof is aligned east-west, which gives us half the roof facing direct south (in South Florida). And no matter how much or little I cover with solar cells, the break-even point is, at best, 18 years down the road (which also includes part of the backyard covered). Even with Lake Worthless Utilities (city-run utility which is twice the price of the state run FPL) solar isn't cost effective for us.

#Comment Re: made: 2008-08-14 22:05:08.18272+00 by: Larry Burton

Well, Dan, unless you retrieved that link from a known busy, busy site I think we just "Flutterbyed" roofray.com.

#Comment Re: made: 2008-08-14 22:55:49.239848+00 by: meuon

Their calcs show a 25 year payback on a $35k system. My calcs give a 5-7 year payback on a $20k 5kw system with a 15% annual rate hike.

#Comment Re: made: 2008-08-15 20:59:32.880614+00 by: Diane Reese

I'm in the middle of active negotiations with two solar firms to add PV arrays to our roofs. The calculations on this site agree almost exactly with the estimtates we're being given for costs and paybacks. So this datapoint suggests they're at least in the ballpark for CA residences at this time.