Friday, November 13, 2009

Type of system and placement

In setting up a garage to install solar photovoltaic system upon, we wanted to know the construction requirements. This included how to face the building, what roof angle would be best, and how much roof space would be required. The roof space question is important to consider with regards to going with a traditional solar panel or a newer technology known as thin panel. Thin panel solar uses an even roof surface like metal and uses this to roll out a thin film of solar "panels". I pictured this being like a roll of tin foil spread out everywhere on the roof. We asked our planned installer these questions, following is his reply.

I have attached the quotes we spoke about on Friday. Your average kWh usage over the given 13 month period is 662 kWh/month. A 5 kW PV system would JUST cover that. You may want to consider a slightly larger system. I have utilized the buy all/sell all program on your quotes to give you a ‘best case scenario’ for the payback question.

The ideal setup is a large roof area facing TRUE south. To find true south, first find magnetic south and then add an additional 8 degrees. In other words, you want the compass to point to 188 degrees as opposed to 180 degrees. The roof pitch would be between 7/12 and 9/12. There would be no shading issues at all-including surface obstructions such as plumbing vent pipes or chimneys. A 5 kW PV system would consume approximately 450 square feet.

The price to install thin-film versus a rigid module system is about the same. However, you would need twice the roof area. So, for the above example considering a 5 kW PV system, we would need approximately 900 square feet. Also, the roof would need to be a metal roof, not asphalt shingles or clay tile. Lastly, we would need to work with the roofer to ensure the ridge cap is modified to allow for the wires to pass through it. I would recommend the rigid modules.

Also, the price for a traditional inverter versus the micro-inverters is about the same too. However, there is a 4 month wait on the micro-inverters. If you really want to expand in the future, I would recommend the micro-inverters. You can still expand with the traditional inverter setup-you would just have to add another inverter in the future during the expansion. This adds a little more to the expansion cost-about $1,500.

There is a lot of research going into renewable energy systems. I hear lots of ideas almost monthly. However, they are research projects and far from market. I don’t see anything new coming within the next few years. However, there is always the chance that someone will invent something next year. It is really a guess.

The price to convert to net metering from a buy all/sell all set up is calculated at approximately $350.00.


  1. Very informative blog Joe. It has helped my education about solar tremendously.

  2. I really like the information provided in this article and I really like the way you have explained each and everything so well. Very well done with the article, hope that you will continue to do posting
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