Ground mount vs. rooftop

[gvl]

Based on other discussions I have going in 2 other threads I'd like to explore a ground install option and keep this thread focused on it.

The main problems that surfaced so far:

1. SE roof orientation that is less than ideal by itself plus it doesn't play well with the current 2pm-8pm on-peak SoCal Edison window.
2. 15 y/o roof which is in okay shape but concerns have been raised I should replace it before installing the panels (I tend to agree).

I can kill these 2 birds with one stone - a ground mount install on a SW facing slope in my backyard. Or can I? Is this likely going to be more expensive than fixing the roof and adding more panels to match my usage? One obvious concern I have is what code says about the wires between the array and the panel, do they have to be under ground all the way? There is concrete on the side that is closest to the electrical panel. I have a cinder-block wall adjacent to the slope, will it be possible to just trench to it and then run EMT on it and then go under concrete only when there is 5 feet to the panel? Any other considerations?

[lkstaack]

Based on 2 other discussions I have going in 2 other threads I'd like to explore a ground install option and keep this thread focused on it.

The main problems that surfaced so far:

1. SE roof orientation that is less than ideal by itself plus it doesn't play well with the current 2pm-8pm on-peak SoCal Edison window.
2. 15 y/o roof which is in okay shape but concerns have been raised I should replace it before installing the panels (I tend to agree).

I can kill these 2 birds with one stone - a ground mount install on a SW facing slope in my backyard. Or can I? Is this likely going to be more expensive than fixing the roof and adding more panels to match my usage? One obvious concern I have is what code says about the wires between the array and the panel, do they have to be under ground all the way? There is concrete on the side that is closest to the electrical panel. I have a cinder-block wall adjacent to the slope, will it be possible to just trench to it and then run EMT on it and then go under concrete only when there is 5 feet to the panel? Any other considerations?

Only your city's building department or a electrician familiar with your local codes will be able to answer your question definitively. I suspect that the only above ground high voltage allowed will be the encased wire attached to the exterior of your house. Everything else will have to be deeper than 18" or 6" if under concrete. Ground mounts usually aren't cheap.

[gvl]

Only your city's building department or a electrician familiar with your local codes will be able to answer your question definitively. I suspect that the only above ground high voltage allowed will be the encased wire attached to the exterior of your house. Everything else will have to be deeper than 18" or 6" if under concrete. Ground mounts usually aren't cheap.

There is an option of trenching on the other side where there is no concrete to the house wall and then through the attic, but it'll be a longer run. I'm probably looking at $10-11k before the tax credit for the roof and extra panels, I suspect this will be plenty to offset higher ground mount costs.

[J.P.M.]

That looks like an expensive and involved option.

[gvl]

That looks like an expensive and involved option.

Is there a ballpark $/wt number for ground mounts or relative cost as compared to rooftop?

[J.P.M.]

Is there a ballpark $/wt number for ground mounts or relative cost as compared to rooftop?

FWIW: I don't know of one. Ground mounts have many more variable than roof mounts. I'd guess that makes the variation in cost of ground mounts wider than for roof mounts, making SWAG's for ground mounts less reliable than for roof mounts.

[lkstaack]

Is there a ballpark $/wt number for ground mounts or relative cost as compared to rooftop?

My ground mount is costing $4.65/w. Compare that to a typical $3.50/w for roof mount. My 5.88 system requires 70' of 20" deep trench dug by hand as well as ten 40" deep posts. Then there is the extra racking, wire, conduit, and a cut sidewalk.

Lots more money, but I'll break even in eight years; just in time to recover the roof I would have had to do now if I went roof mount. And, I'll have a nice cool system that's easy to clean and out of sight.

[gvl]

My ground mount is costing $4.65/w.

And that is using LG280s, spensive... Did you try to shop around? Suddenly a new roof with some extra panels to offset the orientation looks like a very attractive proposition.

[Amy@altE]

Check out the IronRidge online design tool for an estimate of what the racking would cost. You provide the schedule 40 piping (they output the # of feet needed) , they supply the rails and the erector set-like connectors to put it all together. Figure the retail price is around 20% less than MRSP that it spits out. At least gives you an idea of what the physical racking will cost. http://www.ironridge.com/gm

[gvl]

Check out the IronRidge online design tool for an estimate of what the racking would cost. You provide the schedule 40 piping (they output the # of feet needed) , they supply the rails and the erector set-like connectors to put it all together. Figure the retail price is around 20% less than MRSP that it spits out. At least gives you an idea of what the physical racking will cost. http://www.ironridge.com/gm

My installer's SWAG is $8k-12k more which correlates with lkstaack's report. Sounds like ground mount is out.

[thejq]

My installer's SWAG is $8k-12k more which correlates with lkstaack's report. Sounds like ground mount is out.

Looking at the aerial view, it's possible to install tilt mount to get better solar exposure and TOU. Defending on the tilt angle, you can get either S or SW exposure. Not sure how expensive it is, but it should be much less than the ground mount.

[gvl]

Looking at the aerial view, it's possible to install tilt mount to get better solar exposure and TOU. Defending on the tilt angle, you can get either S or SW exposure. Not sure how expensive it is, but it should be much less than the ground mount.

I suspect this will not produce a good ROI as that whole area is in shade at least 1 hr earlier than the hill, so while it may help somewhat it won't be as good as a true S or SW orientation.

[silversaver]

I think you have already decided going ground mount. Good location and orientation, great for SCE's TOU plan.

PS. Just read ground mount is out.... roof mount, you don't want to spend the money on re-roof. So, take your chance

[thejq]

I suspect this will not produce a good ROI as that whole area is in shade at least 1 hr earlier than the hill, so while it may help somewhat it won't be as good as a true S or SW orientation.

But didn't you say "ground mount is out", because of expense? Tilt mount maybe the best option if the price is right. It's hard to know ROI without first finding out the cost which is probably only a few phone calls away.

[gvl]

I think you have already decided going ground mount. Good location and orientation, great for SCE's TOU plan.

No, I haven't. For $1.5/watt extra I might just buy more panels to fully offset my usage, fix my roof and be done.