Ground Mount Vs. Roof Mount

  So you decided to invest in solar panels for your home, and why wouldn't you its a great way to save money and do your part to help the environment simultaneously. You have a good grasp of the technology used and how it all works but now its time to decide where your going to put them. When most people think of solar panels they automatically picture them on roofs. But what they don't realize is that there are also ground mounted systems, each having their own pros and cons.

  

  Their are a few things that need to be looked at in if a roof mounted system is what you have in mind. The first and probably most important aspect that needs to be taken into consideration is, whether your roof will allow your panels to have the optimal southern sun exposure while also not being obstructed by shade form other nearby objects like buildings or trees.  Also does your roof provide enough space  for the solar panels. A 1000 watt system may need 100 – 200 square feet of area, depending on the type of PV module. If you did the measurements and your thinking your roof has the square footage needed, keep in mind the design of your roof as well as any  extras it may have (chimney, sky lights etc.) that can potentially affect the amount of usable space and cost of your system. Now if everything checks out and your roof is suitable for a roof mounted PV system then you can now move on to the next step, but if you find that it isn't or the cost is too high given the above conditions (or lack there of) a ground mounted system may be your future. 

(image:http://kissmyface.typepad.com/photos/green_power/sun-powering-our-solar-panels.html)

  Ground mounted systems make panel orientation much easier because they can be built to face any direction to maximize sun exposure. Cooler temperatures are ideal for solar panel use. If you have the space for a ground mounted setup air flow is much greater under the panels in comparison to their roof counter parts so there is a slight performance increase, although not significant. It does take more materials to build a ground system because it needs a place to be mounted and the wiring needs to be trenched to connect the panel(s) to the house. 

Lets review the pros cons:

Roof-Mounted

Pros :

• Depending on the pitch and orientation of your roof, it may be possible to install the solar panels out of view.
• Beyond standard equipment, rooftop solar energy systems typically don’t require a lot of additional racking and other mounting hardware that's needed for ground-mounted systems.
• Solar roofs make productive use of space that would otherwise go unused, as noted above.
• Related to the previous point, solar roofs don’t eat up land that could otherwise be productively put to use. This consideration is particularly important when it comes to larger commercial and utility-scale projects, which can take up multiple football fields’ worth of space. 

Cons:

• Shade, from trees or nearby buildings, can be a real problem.
• Sometimes a roof is too small to accommodate enough solar panels to suit the family’s energy needs.
• Roofs with lots of contours or other funky shapes can see increase costs associated with solar energy system design and installation. In the worst case, oddly shaped roofs don’t have enough uninterrupted area to accommodate the panels.
• It can be a bit more expensive to install solar panels on some kinds of roofs (like clay tile and wood shake shingle roofs) than it is on others (asphalt shingle).
• It can be kind of a pain to clean/rinse off the panels. Usually a rain shower does the trick. But if you live in a low-rainfall area that gets a lot of dust, this may be a consideration.

Ground-Mounted 

Pros :

• It’s relatively easy to optimize the placement of the solar panels in order to maximize their electricity output. Unlike a roof -- the pitch and orientation of which is already set -- a ground-mounted array can be built so that it captures the most sunlight possible throughout the year.
• While unusual for residential projects, it’s possible to install a tracking system with a ground-mounted system. (Note, too, that tracking systems increase the cost of solar installation.) 
• Solar panels perform best in cooler temperatures. More air tends to circulate behind the solar panels of a ground-mounted array than those of a rooftop system. Because ground-mounted panels manage to stay cooler, they often outperform their solar roof counterpart. (The difference in performance, however, is admittedly not that noticeable.)

Cons:

• Ground-mounted solar systems typically require additional racking and mounting equipment, which can increase the cost of solar installation.
• There may not be enough usable room on your property to accommodate a ground-mounted solar energy system.
• It may not be possible to find an inconspicuous area to install the solar panels on your property, which may prompt aesthetic objections by you (or your family members). Usually, however, a solar installer can work with you to design an array that addresses these concerns. 
• Ground-mounted solar energy systems may come with added costs for trenching. “Trenching” means digging a trench to bury the electrical wiring that runs from the solar panels to your home. If you live in an area with really rocky soil, or there would be a long distance between the solar panels and your home, the added costs for trenching and burying conduit could be substantial. 

(getsolar.com)