Ground-mounted vs. rooftop solar
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ranson
| Posted in Mechanicals on
If you have a lot with plenty of unshaded open space, is there any reason to choose rooftop solar over a ground mounted array?
–John
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Replies
I looked into it and ground mounts were more expensive for a given amount of nominal power production. If the appearance doesn't matter, I'd get quotes for both.
I like having the panels out of the way on the roof. Ground mounts are easier to clear snow from, but might be more susceptible to damage from lawnmowers or vandalism.
Snow seems to fall off the panels by itself rather quickly. Ground mounts are going to be more expensive because they require a supporting structure, electrical trenching, and longer runs of wire. The have the advantage of being angled for optimum solar gain, (the house roof probably is not). They also don't interfere with the house roof. If your house roof is 1./2 way through its life you don't want to cover it with new solar panels that will last 30 more years. The solar panels can also create new issues with snow sliding off quickly and damaging things below. 2 weeks ago we worked on a roof project where 16 year old functioning solar PV and solar thermal needed to be removed and then reinstalled in order to replace a roof under the solar. This gave me an appreciation for ground mount systems.
Or build a garage or shed or picnic pavilion pole-barn style with the optimum exposure, pitch etc. put a metal roof on it or a shingle roof, and get some value for your "ground mount" expense.
John,
In most cases, your PV modules will last longer than your roofing. Removing the PV modules to allow for re-roofing, and then reinstalling the PV modules, is a significant expense. I would choose the ground mount option if you have the land.
For me, ground mounts were easier to install (I did the work myself) and gave me better solar access. They should also operate cooler, giving more energy output in summer months than similar roof mounts, are easier to clear snow from, and can be built so the angle is seasonably adjustable. The adjustable angle isn't critical but it does mean that I can make them more vertical in the winter so they shed snow much better. And the consideration of life of panels versus life of roofing is an important point also.
John,
There was a recent thread here on GBA (29Jan2016, .../55776/would-5000-investment-rooftop-solar-make-economic-sense, use the Search function) that had a discussion about ground-mounted vs rooftop solar, and also a lot of functional design suggestions to minimize costs, even if the installation of solar is delayed for some period of time after the initial build. You may find it informative.
Personally, I'd like to keep the panels off of my house, and probably using Joe's idea of a separate garage, pavillion, etc.
Edit #6...when you look at that thread, start with response #7:
"...if I am building a new house, what simple, inexpensive steps should I take to prepare for a possible future solar installation, if any?"
Like Martin, after living with solar for 30 years in different locations and installing most, I'd go with ground mount for sure and especially if you're in the north with snow. I see most roof mounts sit with snow most of the winter. If it sags to the bottom without coming completely off the module, it really takes down the amperage. Much easier to control and clean when near the ground. HOWEVER, new codes require a 6 foot fence around the array so it may not look pretty unless the wiring and junction box is over 8 feet where someone can't easily get to it as on a large tracking device. Trackers can give you almost 25% more power in a day but only work well when you have sun from E. horizon line to W. horizon line. If you're out in the country away from others, then you can easily make your own tilt-able rack after you have a footing assessment done for a good base.
In June 2010 I installed my own 5.28 kW system and chose to ground mount. My roof was not oriented well for PV and it would have been a lot more difficult for me to install the panels on the 2 story roof. I had plenty of space along the north fence line for my 24 panels and the trench was less than 60' long. I used a central inverter so voltage loss was minimal using 10 ga. wire.