Helpful? 0

Where shall I place my PV panels?

My new house is in the design stage. Mid-coast Maine, about 20 miles from the ocean, zone 6.

Good southern exposure. Standing seam roof, oriented about 10 degrees west of due south. 8/12 pitch.

Here's my question: Is there any benefit to placing of panels on the roof as opposed to a ground mount? I have plenty of room on the ground.

An obvious benefit to mounting them on the roof is they'll be out of sight, whereas a ground mount will be much more visible. On the other hand, on the ground I can clear snow and wash off the dust. I suppose a ground mount could be set up to adjust the angle once in a while as the sun angle changes with the seasons, but what sort of mechanism is needed for that?

Asked by stephen sheehy
Posted Mon, 06/30/2014 - 16:35
Edited Tue, 07/01/2014 - 07:26

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16 Answers

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1.
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About the only advantages to roof mounting I can think of are possibly lower mounting hardware costs, and possibly lower hardware costs (less cable possibly). The advantages to ground mounting are like you said higher seasonal efficiency, and your fire department will likely be grateful they aren't on the roof if you ever need them.

Answered by Donald Endsley
Posted Mon, 06/30/2014 - 17:23

2.
Helpful? 0

As long as you keep the panels above the historically deepest snow line, ground mounting can often be cheaper, and are CLEARLY easier to maintain.

Adjustable mounting is usually more trouble than it's worth- spending the difference between fixed vs adjustable mounting on additional panel area tends to have more value, higher return.

Answered by Dana Dorsett
Posted Mon, 06/30/2014 - 17:34

3.
Helpful? 0

Another possible advantage to the roof is clearing trees to the south, but it sounds like that's not an issue.

Are you doing it yourself? If not talk to ReVision Energy, in Liberty, if you haven't already - they can give you quotes for both installs.

Answered by Dan Kolbert
Posted Mon, 06/30/2014 - 19:07

4.
Helpful? 0

Thanks for the suggestion, Dan. Back in the old days, of course I'd do it myself, but I've decided to leave it to the experts. No more climbing on roofs. Liberty isn't too far from here.

Answered by stephen sheehy
Posted Mon, 06/30/2014 - 20:46

5.
Helpful? 0

Stephen,
You've gotten good advice here. Ground mounting is always preferable to roof mounting, as long as:
(a) You have a good spot of land with adequate exposure to the south where the PV array can be installed;
(b) Everyone in the family thinks that a ground-mounted array will look good;
(c) You have checked to be sure that trees and hills to the south of the array will not prevent the sun on December 21 from hitting the PV array.

The last point is important. Here in northern New England, the sun is very low in the sky in late December, and your maple trees may be too high for ground mounting. At my house, the sun just touches the top of my roofing near the ridge in that season, while my lawn is in the shade -- so think about where the sun is in late December before you make your final decision.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/01/2014 - 08:11
Edited Tue, 07/01/2014 - 08:13.

6.
Helpful? 0

Stephen,

I actually disagree with Martin and Dana. If the roof has good orientation and exposure and is in decent shape we tend to recommend a roof mount as a first option. Roof mounting is somewhat less expensive than building a dedicated structure for the array on the ground and it gets the array out of the way (don't have to mow around it or worry about stray baseballs etc). So long as you use high quality hardware and a reputable installer, module 'maintenance' is really practically non existent for PV systems so I wouldn't locate modules based on that. If the roof is reasonably steep (9/12 or better) and is either metal or the solar covers it top to bottom, snow clearing won't be an issue as the roof will clear itself of snow naturally when the sun comes out in the winter. It is true that, all else being equal, ground mounted systems will outperform roof mounted ones ever so slightly thanks to cooler module temperatures, but in our climate that effect is small enough to basically be in the noise.

But I like Dan's advice above (thanks Dan!). Call our office in Liberty and they will happily come out and evaluate the site including both current and future shade, and show you price and performance expectations of each option and then you can make a good informed decision based on your own priorities and goals.

Good luck,

~Fortunat
www.revisionenergy.com

Answered by Fortunat Mueller
Posted Tue, 07/01/2014 - 08:59

7.
Helpful? 0

Fortunat,
Well, I guess we'll have to agree to disagree. I used to work as a roofer, and I still think like a roofer.

Roofers prefer to see PV arrays in the yard, not on the roof.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/01/2014 - 10:13

8.
Helpful? 0

Martin: Is that because it's easier to repair a roof without pv panels on it?

Answered by stephen sheehy
Posted Tue, 07/01/2014 - 11:39

9.
Helpful? 0

Stephen,
Q. "Is that because it's easier to repair roofing without PV panels on it?"

A. Yes. Repair or replace.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/01/2014 - 11:46

10.
Helpful? 0

Since this roof is standing seam metal, it should not need to be repaired or replaced. Plus, you can use attachments which clip to the standing seams, so there are no roof penetrations. On the other hand, ground mount offers easier access and easier seasonal adjustment.

Answered by Bob Irving
Posted Sun, 07/06/2014 - 11:21

11.
Helpful? 0

Stephen,
Just like your car the longevity of the finish on a metal roof is directly related to how clean it is kept. While metal roofs are almost maintenance free, they benefit from having any accumulated debris removed and the occasional wash. If you have the luxury of a spot suitable for a ground mounted display I'd tend to favour it over the roof.

Answered by Malcolm Taylor
Posted Sun, 07/06/2014 - 20:07

12.
Helpful? 0

A quick question: Do you plan on living here for a long time (or the rest of your life)? If so consider maintenance and safety when you are over 60. I am a firm believer in the "age in place" philosophy and planning to make your life easier in the years to come. Going up on a slick metal roof is no fun when you are 30 or 40, potentially disastrous when you are 60 or 70.

Answered by Nathan Spriegel
Posted Mon, 07/07/2014 - 08:54

13.
Helpful? 0

Nathan-we plan to live here for as long as we can. We're in our mid-60s. My days of going up on the roof are past. I leave roof maintenance to the pros. A metal roof sheds snow better than asphalt. Which is one factor supporting the choice of metal.
The house is being designed to allow us to "age in place." One floor, no thresholds, wide doorways, easy to maintain, and so on.
We'll probably wait until we start building to decide where to place the solar panels. I spoke with Hans at ReVision and he'll come out and help us assess what works best, although he suggested roof mounting is usually what he recommends.

Answered by stephen sheehy
Posted Mon, 07/07/2014 - 09:40

14.
Helpful? 0

Thank you all--your insights are wonderfully helpful.
I am 70 and in good health, DH is 71 and also in good health. We are building a small retirement cabin at home in Montana (zone 3/4). We will be using metal roofing. We are in the design stage and right now the focus is on the design of the roof. I like pitch 5 or 6, though I understand 7 would probably be better. We have been home now for 4 years and I still have not seen any snow fall as deep as we used to have in the 1970/88 times. I think the deepest we got last year might have been 3 feet so I am comfortable with a shallower pitch. Like Martin I prefer the Japanese style roof--simple is best. However, I would love to have two covered areas running the long side of the building about 34 feet.
Questions:
1. Because the building itself will be narrow 16feet. What is the shortest roof covering (overhang?) we should use to be able to sit in the shade?
2. I do not like a very wide roof and would like to somehow build the porch roof separate from the building roof--what is that called and what are the issues with having separate roofs--the porch roof being attached to the building and not to the roof.
3. Are there ratios in the Japanese style?
4. Our cabin is facing due south--given that it is a small space what is the best number of panels?
5. MOST IMPORTANT: DH is enamored with SIPS and wants to use them for walls and roof--do you have any thoughts about this? I would like to have the interior space open to the ceiling--given that we are both kind of short it might be possible to do 9 foot walls and thus lower the ridge line a little. That would be nice to keep us from being visible from the highway and maintaining the unbroken view for passers by.
Thank you for your time and insights--they are much appreciated

Answered by Anne Lee
Posted Mon, 07/07/2014 - 12:28

15.
Helpful? 0

Anne- I suggest you repost your questions as a new question under General questions. That way, more people will see it and you should get more responses.

Answered by stephen sheehy
Posted Mon, 07/07/2014 - 13:57

16.
Helpful? 0

I'm with Martin on this, roofers hate PV panels on the roof. Having dozens of additional holes in your roof to attach the panels is not good either. Speaking with firemen, they also hate PV panels on roofs. If a panel ever goes bad, climbing up there is not fun, especially in the winter or summer.

If you have the room and trees are not in the way during winter, go with the ground mounted. Most people go for roof mounted because they can't do the ground mounting due to limited space in their yards. So roof mounted panels are the default method for most homes due to limited yard space.

Answered by Peter L
Posted Mon, 07/07/2014 - 18:41

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