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Just finished the installation -- 14 LG 305w panels, Solaredge 3800 inverter:
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What is your yearly use ?
Predicted output ? Any actual output numbers yet ? Orientation ?
Cost for this setup ?
Just that some people in your area are going to want to know for sure.
Are those panels tilted and sitting on a flat roof ? Did the install company say anything about the mounting on a tilt costing more than if they were flat mounted ? Just wondering about that.
Are you happy ?Comment
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Our current usage is about 600 kwh/month.
Predicted usage: Clean Solar gave us a production guarantee of 5,952 kwh for the first year. I'm hoping to get somewhere about 6600 kwh, based on the PVWatts estimate. We're still waiting on PG&E, so I don't know for sure what kind of production we'll get.
The roof is flat. Azimuth is 171 degrees. The four panels in front, in landscape orientation, are titled at 18 degrees. The rest of the panels are at 15 degrees. CS told us that was the greatest angle the city would allow.
Cost was $20,775 up front. It was way on the high side because our house is three stories tall, which required CS to use a lift gate to get up top. I was willing to pay a premium because I wanted a well-established installer who will still be around if issues arise down the road.
The workers were professional, and the installation looks good. My main concern is the integrity of the roof. It's a torchdown job over TJI 230 joists and 5/8" plywood. I'm concerned about leaks. At this point. the stanchions and flanges look well-sealed. We'll see what happens if/when El Nino shows up.
I'll report back in a year and let you know how happy I am with it.Comment
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Excuse for perseverating about tilt here but just curious.
Why are the front panels tilted more ?
How far apart are the rows set ? Is it so they won't cast shadows on each other ?
Still wondering if that tilt mounting was any big deal or presented any big challenge for the installers.
Cool, I spend a couple of summers up your way playing h2Opolo at Cal, way back when.Comment
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The front (landscaped) panels are tilted more than the rear (portrait) panels because the latter would have cast shadows on each other if they were tilted higher. That's what I'm told, anyway.Comment
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Adding:
I don't know if the tilting was any big deal or if it cost extra compared to a slanted roof. I never asked them because it wasn't a factor for me -- the roof is flat and there's nothing I can do about it.Comment
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I will hazard a guess and say that the amount of tilt may have something to do with the "final height" measurement at the top of a panel which is probably limited by the city codes.
The panels mounted in portrait might be too high at an 18 d angle so 15 sounds like the max allowed.
Since the front row is landscape using the shorter side in the height measurement it could use a bigger angle and not exceed the "final height" limitation.
All guesswork on my part but I have run across limitations of roof mounted equipment on some projects so it can't be seen from the street level.Comment
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Yes, exactly.
What is the purpose of these codes in this instance, I wonder? As you can see from the photo, the array is surrounded by a parapet on all sides, so they're not going to be visible from the ground (or even from a second story building) even at 30 degrees of tilt, and the wind is a non-factor. I don't get why there was a height limit, but that's what the installers told me.Comment
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Local and state codes are sometimes hard to figure out. They are usually put in place to increase safety but sometimes (because of pressure from the populace) they are there to make people happy about what they see or don't want to see.
I saw the parapet in the picture and not knowing the actual height the "rule" may be as simple as "anything on the roof must stay XX inches below the top of the parapet". Although that would make it hard to install large AC unit but would limit antennas and satellite dishes.Comment
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Bah.... it's totally stupid. Someone doesn't want to see my solar panels, therefore we must limit their efficiency and burn coal to produce the power instead? (Obviously I'm not blaming you, just venting.)
You should see some of the other properties in my neighborhood (northwest Oakland). The people next door basically operate a junkyard; it's a million times the eyesore that solar panels could possible be (especially since it's impossible to see the panels from the ground.) But try and get the city to do something about that...
I wonder how much work it would be to get a variance and increase the tilt, or whether it's just not doable at this point.Comment
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I don't know what it would take for a variance or what the cost would be to increase the angle compared to the potential increase in production during the winter months when the sun is lower.
I went back and looked at the photo again and there is a sat dish sticking above the parapet so the "height limitation" (if any) is not associated with everything on the roof. It might be related to wind calculations but again I am totally guessing.Comment
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A variance may be one possibility.
But, if you increase the tilt, you will increase the required pitch between panels. The result may be that you might not get as many panels in the same space, with some saving grace that the most northerly can be up against /past the parapet To a 1st approximation (only), when putting panels on a horizontal surface, a rule of thumb for a very rough 1st guess because of self shading or shading from panels closer to the equator, total panel area will be limited to something like the roof area time the cosine of the tilt angle. That works best for low tilt angles and is in no way implied as a substitute for a more thorough analysis. See solar textbooks dealing with self shading or software such as SAM or TRYNSYS for more details.Comment
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