Is this a bad layout for panels on my roof?

dariushd
dariushd Registered Users Posts: 5
During the 4 winter months, give or take, shadows being cast from trees lining my property are pretty long and will fall on a few panels that are being designed on my roof. How badly will this reduce my power output and is it a bad idea to have those panels there if they could get 10% or so shading from these trees during just those few months? This photo pretty much shows the longest these shadows get for the most part. I'd like to avoid cutting the trees, but would like to get 21 panels on the roof.

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I am concerned a little with this layout, and I admit I may be making a mountain out of a molehill: but wouldn't panels #4 (shading from our AC unit on the roof), #11, #18, and #21 get hit with enough shading from the trees during the winter months to essentially render them useless? Wouldn't even a little shadow dramatically decrease the output from a panel? I read one article where less than 10% shading from a fence knocked someone's panel output down 75% while that shadow was on it.
I will be using enPhase microInverters, so it won't knock out the whole grid or anything like I understand a single inverter might, but is it a waste to have those 4 panels if they are pretty weak for 1/4 of the year even with microInverters? Am I over-thinking it and the benefit from those 4 panels outweighs the loss in winter when those shadows are as long as the image attached? Or is the shading on those panels not that terrible on the output?
Thanks so much, I really appreciate any feedback.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Is this a bad layout for panels on my roof?

    As long as you are using micro inverters (like the Enphase)--Nothing wrong with layout.

    You can review your rate plans for GT Power--In California, we (I think) need to have Time of Use billing--Which pays us about 3x as much money for late morning/afternoon power vs early morning power (plans/requirements/choices can be very complex... Need dto confirm with your utility to see what makes sense for you).

    For me, mounting more array on the west and south faces is more cost effective (on my home).

    Regarding trees... They will continue to grow (it appears). In ten years, they may be another 10-20 feet taller (if these are fast growing trees).

    Eventually, you will have to do something if you want to power (top them--always a bad idea, replace them with something else, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    Re: Is this a bad layout for panels on my roof?

    Your layout is about as good as you can do without off'ing those trees. From a cost effectiveness standpoint though, some of those panels (1,2,3,4) will take a long time to achieve pay-back. I really never put panels oriented on the north half of the compass. Looks like you should be able to move the east facing rows up right to the peak and get two rows of them above the little dormer. Can you move them right to the north edge of the roof (or are you getting burned by the fire access 3ft rule)?
  • dariushd
    dariushd Registered Users Posts: 5
    Re: Is this a bad layout for panels on my roof?

    Yes, it's the setback rules that is pinning us into this layout, we can't get any closer to the edge. Panels 1-4 are on a West facing roof, so that shouldn't be too bad, right? Not that much less than East facing (or south facing, of course), but not bad ( I live in Southern California). If those trees weren't there (it'll cost me $2500+ to cut those trees) I'd have about 6 panels on that south facing roof in an instance, but the ROI on cutting threes and only getting 4-5 panels on that roof didn't calculate. As I see it, this system will pay for itself in about 9-10 years, not counting the increase in my house's value, which pays for itself on day 1. The panels are SolarWorld 275 Mono and using EnhPhase 250 microInverters, that should offset us a good 70-85% on average. I don't think I could fit anymore on there without more shading issues from trees or stuff on my roof. Any more panels and I'd have to cut those trees for good.
    I wonder if I could make a pergola in my backyard and put some panels up on that, anyone here do that? Or do panels have to be part of the house structure?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Is this a bad layout for panels on my roof?

    Yea, costs $1,500 to get a licensed tree trimmer to the house. Trees cause loss of power, but not worth the cost of cutting them.

    I usually justify cutting/removing the trees is from wind damage (grew up in a valley with lots of very tall/older trees.. Seen more than a few homes and cars bisected by a downed limb or tree).

    In my area, once a tree gets more than a few inches in diameter, the city now "controls" the tree (even on my property). Costs $100's for a permit and more $100's to buy 25 gallon replacement trees... Now, no new tree has a chance on my property (whether I like trees or not).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1
    gww1 Solar Expert Posts: 963 ✭✭
    Re: Is this a bad layout for panels on my roof?

    Man, I love where I live. No permits for anything, no inspections and not many rules. The only thing that modivates me to do anything correctly is pride and wanting to do good. I have a son in law that just built a mansion and had to get an occupancy permit just to move in. I have lived in houses with a matriss on the floor in one room while I remodeled the rest of the house cause I couldn't afford to do it any other way. I am not putting anyone down but it is so strange to me that I don't know if sociaty would accept me if I lived in a place that I always had to ask first.

    You gotta do what you gotta do but I would cutt all my trees too if some one else could make me spend money cause I had them.
    Cheers
    gww
  • dariushd
    dariushd Registered Users Posts: 5
    Re: Is this a bad layout for panels on my roof?

    You know, I figure this is the most most efficient I can get with 21 panels, factoring how the shadows will move through the day from the AC and chimney. This way I'll get one out from my AC's shadow even better. But yeah I think this'll be the way we go. Very excited to do this. I find it hard to believe everyone doesn't have solar on their roof, it's such a boon to the power grid. This should be a good 7600kWh per year. Wish us luck!

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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Is this a bad layout for panels on my roof?

    just a point to note those trees ARE ALIVE and WILL keep growing, in a few years they will start casting longer shadows!! and affect ALL your panels, save some money and grief later by having a tree topper come and lower their height so they do not cast ANY shade on the roof right now,preferably at the same time of day that aerial photo was taken, and you will get a few years of peak production.

    hth, a Forester.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • dariushd
    dariushd Registered Users Posts: 5
    Re: Is this a bad layout for panels on my roof?

    Yeah, that is very true. I was hoping to delay that for at least a year when I planned on adding solar water panels for my pool, which would necessitate cutting the trees down to my roof line. Saving my pennies for that.
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Re: Is this a bad layout for panels on my roof?
    BB. wrote: »
    In my area, once a tree gets more than a few inches in diameter, the city now "controls" the tree (even on my property). Costs $100's for a permit and more $100's to buy 25 gallon replacement trees... Now, no new tree has a chance on my property (whether I like trees or not).

    -Bill

    Just insane how government has gotten.
    Those trees look like cypress ,Leyland Cypress
    Here we are allowed to manicure trim them gently , Im sure you are also.
    Some of my not so gentle trimming comes from a stihl and i take a little off the top , Say 150 foot .. Those are the noisy drops.
    Just last year I had to trim out our Laurel Hedge , started with a trimmer & ended with the stihl (smaller unit than the 150 drops) .

    I would trim small amounts & clean weekly till you & the neighbour are satisfied . Once you start taking the tops off . they will bush out .
    So getting into a system of rolling out a drop rug , & a quick trim & cleanup should keep all happy .
    Don't tell me Home /lowes don't sell electric trimmers in CA .

    I won't be leaving our laurel hedges years between trims . 4" stems was more than our cordless trimmer could handle ;)

    We have some ceder trees that have a height of 18 feet , round balls tops (after trimming ) with a 12 " trunk .
    Trimmed after topped ..

    The larger the tree , the more $ to deal with them . I live in a forest , I needed to make sure that during our changing weather patterns , I didn't need one hitting one of the buildings during the wind storms . Beside the Stihl , I cheat with excavators 30T , tractors ,woodmizer etc.

    I would deal with those trees slowly & neighbourly quite . As with Panels 1-4 why not square bloc all four the keep away from the AC unit ..


    VT
  • dariushd
    dariushd Registered Users Posts: 5
    Re: Is this a bad layout for panels on my roof?

    If I put 1-4 in a square block, they'll get hit with the chimney shadow, so I have to keep them up high on the roof pitch away from both AC and chimney. As far as the trees, they are "Italian Cypress" and are about 35' tall, way too high for me to trim them myself. Plus there are 16 of them in a tight row acting as a fence between me and my neighbor, who is happy to havbe them cut down, too. I figure slash them to the eaves line of my roof and then once or twice a year, trim them back down as they grow. Other option is to cut them to the ground and build a fence, which will cost 2.5-3 times as much.
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Re: Is this a bad layout for panels on my roof?

    I would use a pole saw , rented from a rental shop if I didn't have one (i have gas stihl screamer & a Black & Decker cordless & Quite) , start on the top & take off 5 feet at a time quietly if the neighbour will help , electric trimmers after that if you can keep the end result at ladder height 12-14 feet. Cypress don't have large diameter trunks at the 20 foot height , then a few more cuts to take down in small bits. Last cut needs to be angled cut facing down so rain flows off & drop black pitch on the cut to heal it It will live , trim again next spring the crown growth.

    Now i see the chimney , whats that for ? don't tell me you have a fire place but can't burn wood ? Cuz that cut stuff makes a nice outdoors fire pit in the evening , a few bugs around , throw on the green clippings .

    I'm having you on ;)


    VT
  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Is this a bad layout for panels on my roof?

    I had a similar situation at my house. A row of dying cedar trees shaded a prime portion of my South facing roof, and dropped tiny needles on my camper, and on the neighbor's cars. Though they were on my property, I talked with the neighbor about me removing them, and putting up a vinyl privacy fence. They were not only onboard, they even offered to help pay for the project. I declined to accept anything since it was on my side of the property line.

    dscn6523.jpg

    1379757_10202542550430962_1400509974_n.jpg

    Afterwards:

    dscn9476.jpg

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    I own a portion of the woods behind my house, and it's a conservation area. So I had no concerns of making a wooded lot barren. Not shown is the PVC privacy fence, and happy neighbor! Each location and situation is different, but I'd suggest at least considering taking them down, and replacing with something shorter.
  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Is this a bad layout for panels on my roof?

    I finally uploaded a pic of the fence installation. The messy trees are gone, plenty of sun exposure to the south side of the roof. Lots more room for solar, and still have plenty of trees out back.

    house-fence-solar.jpg

    Good luck with your decision. When you trim, remove, or replace the trees, please post pics!