Looking to go solar...everything looking good, am I missing something?

[J.P.M.]

See comments in bold:

Equal size systems produce the same annual output - initially and for some yrs. down the road. I'd suggest A more important efficiency to consider may be PRICE or COST efficiency, including the cost advantages gained by conservation efforts which can first of all lower the bill and then also reduce the optimum size system, thus making possible a less expensive panel with a lower area efficiency that will now fit on the smaller roof.

The lower yearly degradation of S.P. is acknowledged. It can and is being dealt with, but really needs a life cycle cost analysis to be done correctly, and is probably not amenable to blanket statements without gross oversimplification of the type necessary for this forum. One way to consider such matters is figuring out the "levelized cost of electricity". PITA, but it puts things on more or less equal footing, or can do so, depending on smoke/mirrors of perpetrators.

[J.P.M.]

Haha good point about the discontinued stuff. And I agree, the internet monitoring is an absolute deal breaker for me. I love that kind of stuff...I check my Nest thermostats all the time. SunPower is starting to look better as we could have more kWs facing the south direction.

Everybody's got internet monitoring. Nothing special.

[Ian S]

The problem with the TOU stuff is that the local electric company separates that so you can't apply power produced during TOU hours to non-TOU hours.

I took a current photo showing the relation of the neighbor's house to our southern facing roof, not sure if it can really tell us anything.
Here's the photo from the east, looking west.

OK, I can see where that could be an issue. I'm surprised the one guy didn't see any problem. Maybe if you asked nicely, your neighbor would lop off his second story.

[HX_Guy]

I figured out how to turn on Shadows in Sketchup (this program is pretty damn powerful and useful!) and just with a rough box to represent the neighbor's 2 story house (I guesstimated 23' to the roof, could be less) but it looks to confirm what the guy found today using the SunEye...

10:00 am


1:00 pm


3:00pm

[silversaver]

If you got that much of shade, nothing can help you......

[HX_Guy]

If you got that much of shade, nothing can help you......

[JCP]

Can always move to a new one, or build a second story on top of your house.

[J.P.M.]

I figured out how to turn on Shadows in Sketchup (this program is pretty damn powerful and useful!) and just with a rough box to represent the neighbor's 2 story house (I guesstimated 23' to the roof, could be less) but it looks to confirm what the guy found today using the SunEye...

10:00 am


1:00 pm


3:00pm

Nice . Sketchup does seem quite useful.

A thought or two:

To get a perhaps better idea od garage location, heights, etc, Go out some day and measure where the garage shadow falls on your south roof. Then, vary the dimensions the software uses until you get a match in 2 dimensions. If the software adjusts for lat./long. and date - solar time vs. civil time, you might get a better guesstimate.

Looks like your south roof is not super good. Any thought to placing south facing panels on the north face of the northern section of your garage ? - that is, have panels facing south on an otherwise unobstructed north facing roof ? South face of garage may have some possibilities too. Just sayin''.

[wwu123]

Interesting, I have the same issue. In winter time here in socal we may have big fluctuations in outside temp where it may get into 70's during day but then cool at night down to 50 or even lower. Still what happens in my house is the second floor gets hot at night while it's cold outside. And the attic temp is cool (I have a remote thermometer). If I cool it down either by AC or by opening a window and whole house fan it will cool temporarily but after I shut the window or turn off AC after a while the second floor is hot again. I don't understand where the heat is coming from. Haven't heard this term "thermal mass" before, i'll have to look that up and see what that means. My house is a stucco house as I suspect the AZ house is as well.

Not really that much of a mystery when you think of all the dense material (thermal mass) in your wall studs and floors has been baking in the heat all day and holds way more heat energy than just the "light-as-air" air in the room. If you merely replace the hot air in the room quickly, the warm walls and floors will quickly start warming up the cooler inside air once again. For example, if you install a whole-house fan, a properly sized one can exchange out the entire volume of air in your house and attic with cooler outside in in 3-5 minutes. But that's not going to cool down your house if you then shut it off - you have to keep running it for a few hours to exchange new cool outside air continually that will soak up the heat slowly from the walls and floors.

Ever go to one of those newer "hot stone grill" teppanyaki places where they give you a superhot stone and some raw slices of steak and shrimp? The hot stone is your house after a long summer day, cooking everything coming on top of it including the air and the meat for a good 30 minutes (the poor raw shrimp being the analogy for you cooking inside your hot stuffy house...)

[silversaver]

Save your money with string inverter, you might have less roof spacing now.....

[wwu123]

BTW, there's another poor man's way to do this as well with an iPhone. Download a free app called Skyview Free. In the free version, you can tell it you want to chart the Sun. You look at the sky via the iPhone camera and the app will superimpose the path of the Sun over wherever you're pointing the camera - change the date in the app and it will show where and when the Sun will be obstructed by the neighbor's house. I've used this to map my similar WInter shading. (Credit for this tip goes to http://www.builditsolar.com/References/SunChartRS.htm)


To me it looks like you have plenty of choices. First you have other south-tilted roof planes (that are not on the south end of the house) that are not shaded in winter or apparently anytime of year, seems like you could fit 12-15 panels there easily (I similarly have half my array on a south-tilted roof on the north end of the house). Second, you do have east and west options - I think the rule of thumb is you get about 80-85% of the perf vs south facing, not horrible and many here have east and west arrays.

Lastly, if the winter shading is just causing you to lose half the day's production from Nov-Jan, it still may be a wash compared to east or west arrays, which again many find acceptable annual production. The top row in landscape may even be clear of the neighbor roof much more quickly than the bottom row over the season. If you use the Sketchup technique, you really need to get the height and distance of the neighbor house pretty accurate, at those acute angles even a few feet off is going to give very different results. If you use the iPhone technique, survey at several points along the wall and make sure you're on a ladder up towards the roof - again the angles are very acute and the results will vary considerably just a few feet away.

[HX_Guy]

Thanks for the info Wwu, I'll look into that app. I'm not seeing how it would work with the neighbor's house though, or maybe the app has settings for surrounding structures? I'll see.
I guess I'm in no hurry and worst case I'll just wait a bit and see for myself come this winter exactly what shade there is, take good photos and such and then setup everything for early next year.

About the other south-tilted roof planes, the area looks quite big but unfortunately the city I live in just very recently, like in the last couple months, passed some new fire code rules that says panels have to be at least 3 ft from the tops edges of roofs and 1.5ft from the sides so it really limits the space. The couple companies that have come out and taken a look have said we could basically do 6 panels on the left side and 2 on the right side at most. Originally I didn't want to do any panels facing west so they wouldn't be seen from the street but I am considering it if really needed, though again I had one company say they couldn't put any there because of too many vents on that side. There are zero vents on the east facing plane and just 1 vent on the south facing plane on the south side of the house which is why that would have been so so ideal. I think I'm more bummed out about that than anything, I thought it was the ideal situation with that whole long south span and then my bubble got burst.

[wwu123]

Also just eyeballing your aerial photo, if that is indeed on Nov 6 mid-morning, you can just see the neighbor's roof shadow start to clip the bottom of your roof, which means at noon it's not shading at all. So you definiltely have no shading issue at all before Nov 6 and conversely after Feb 4 or so, that's your worst case. More likely it's much better than that, and maybe there's no shading at all on the higher of the two rows.

FWIW, I followed the shading of my arrays by the neighbor's eucalyptus trees (about 100 feet away, but they're like 70' tall!). The shadows started to obscure around Nov 17 for me, by Jan 25 I'm all clear. For the upper of my two rows, the shading is only from Dec 1 to Jan 10 or so, nearly a month less than the lower row. During those days I still get no shading from those trees until mid-day, so I can still get a half-day of production.

What might annoy you more is that tall vent stack (pipe) on top of your neighbor's roof peak. That looks like shadow would sweep over a couple of panels during most of the day, and for several more months than the roof. If that small shadow covers just part of a panel, it can negate the production for the entire panel.

[inetdog]

I do not think that the app shows you a picture of your neighbor's house.
Instead you use the camera on the phone to put up a picture looking from your panel location toward your neighbors house and look to see where the sun trajectory imposed on that picture by the app crosses your neighbor's house, trees, etc.

[wwu123]

Thanks for the info Wwu, I'll look into that app. I'm not seeing how it would work with the neighbor's house though, or maybe the app has settings for surrounding structures? I'll see.
I guess I'm in no hurry and worst case I'll just wait a bit and see for myself come this winter exactly what shade there is, take good photos and such and then setup everything for early next year.

About the other south-tilted roof planes, the area looks quite big but unfortunately the city I live in just very recently, like in the last couple months, passed some new fire code rules that says panels have to be at least 3 ft from the tops edges of roofs and 1.5ft from the sides so it really limits the space. The couple companies that have come out and taken a look have said we could basically do 6 panels on the left side and 2 on the right side at most. Originally I didn't want to do any panels facing west so they wouldn't be seen from the street but I am considering it if really needed, though again I had one company say they couldn't put any there because of too many vents on that side. There are zero vents on the east facing plane and just 1 vent on the south facing plane on the south side of the house which is why that would have been so so ideal. I think I'm more bummed out about that than anything, I thought it was the ideal situation with that whole long south span and then my bubble got burst.

The point of using the app is to see where the sun's path crosses your neighbor's house visually - it will draw the path of the sun on the screen for you, overlaid on camera image of the neighbor's house. It uses the tilt sensor and compass of the iPhone to determine where you are pointing the camera, and where then to overlay the sun path on the camera screen. The app does not know of your neighbor's house or anything in the camera's view, that's why you have to look at the realtime camera image yourself - but it will be self-explanatory once you try it, and how you can tell exactly the time of day the sun path will cross behind the obstruction.