Before being able to install solar panels on any roof, performing a solar site assessment is critical in order to properly design a solar system.
From a sales perspective, it is key to know what to look for instead of wasting any time on roofs that are not well suited for a solar system.
Although spotting a good roof can be pretty easy, spotting a bad one is a little more of an art, so here are the top five things to look out for in a roof that may not meet solar site assessment standards.
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Shading
. The number-one talked-about aspect in solar installation is shading, but why is shading so important? If a roof has full sun for one hour with 8 Sharp, 208 watt modules, it will be produce 1200 watts-hours. If just one cell, in one module is shaded, production will drop to 1100 watts. If one full module is shaded, this figure drops to only 900 watt-hours. Note that a single cell is about two by four inches. A lot of roofs will fall into two categories; no shading at all or completely and obviously shaded. For determining whether or not to install on a roof in the middle of the spectrum, use a Solar Pathfinder.
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Old Roof.
Regardless of how much power an installation is able to produce, if the roof leaks, the outcome doesn’t matter. Also, once solar panels are installed, replacing a roof with panels on it is doable but a pain, and can be costly. Make sure to check the age of the roof and get the information for the warranting contractor if there are any questions. If the roof is in really bad shape, the homeowner will want to replace it before panels are installed.
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Obstacles.
Don’t get too cocky when looking to design a solar system around obstacles. If there are too many hindrances on the roof, panels may not fit, and it could be too troublesome to work on that roof at all. Some examples of obstacles are chimneys, stink pipes, complicated architecture and sky lights. This may not be the biggest deterrence in the solar site assessment, but it’s important to keep in mind when determining the probable success of the project. Having obstacles that completely hinder a project are rare, but they do occur.
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Electrical Service.
Most residential inverters need 20, sometimes 25, amp breakers for over-current protection. A homeowners existing service may not be large enough or have enough bays for a new breaker. It is vital to determine these limitations before starting to design a solar system. Similar to obstacles on a roof, electrical service will rarely mean a installation cannot be done, but it might make it more expensive, something you’ll want to keep in mind when quoting.
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No Place for Conduit Run.
Keep in mind that power needs to get from the roof down into the basement in order to tap into the existing electrical service. If the home owner is strictly against an outside run on the house for aesthetic considerations, if there is no attic, and if the entire inside is finished space, it may be impossible to get the power downstairs. This is rarely a deal-breaker but something that must be discussed upfront.
To go deeper on solar sales, marketing, installation, and design, check out HeatSpring’s free and paid solar training courses.
For more on solar site visits and assessments…
Safe Roof Systems builds and installs roof deflection systems for property owners concerned with roof loading from snow and ice – even ponding water. We have been helping property owners for many years, but more recently we have been approached by Solar project leaders as a way to help insure the safety of the panel installations and the buildings they are mounted on.
Most solar panel makers offer details on the over-all weight of the systems (usually very light – 3-6lbs per/sqft), but the collateral weight of unclearable snow and ice is the concern for the building owner.
“how do you clear a overloaded roof of snow and ice when it’s covered in expensive solar panels?” You cant cant scrap ice off them with a shovel (or probably shouldnt) and the shodows caused by angled installations can create snow and ice damns that create localized roof deflection problems.
Our technology can help this industry tremendously and I look forward to an opportunity to discuss this with you in greater depth.
Please fell free to contact me any time – cell= 774-766-1389 or by email on ccollings@saferoofsystems.com
very best regards,
Chris Collings
Safe Roof Systems Inc
Chris,
We normally don’t post promotional comments, but this seems like a relevant and genuine contribution to the conversation. If your solution solves a real customer need, I’m happy to see you have success. Thanks for reading the magazine and looking for solutions that help the solar industry grow.
All very good advice!
One potential solar PV solution that would eliminate most of the problems associated with roof installations, and the high cost of ‘boiler plate’ ground mounted installations, would be a linear PV module installation along an 8′ high chain link fence at 2′ above ground level with a second set of short driven fence posts as the forward lower anti-frost action support and with the 8′ existing fence posts providing the back upper level support. Yet, I have been unable to find much in the way of off-the-shelf hardware to facilitate such a design. If anyone knows of such a fence post mounted installation, or adaptable hardware, I think this could provide more potentially viable PV solar suitable sites..not to mention lowering the cost impacts of adapting to non0suitable structures.
Could you talk a bit about the impact of: 1) heavy snow, 2) the microprocessors on the market that some desingers use to mitigate the watt hour reduction of shading.
Dave,
Really great questions. I can’t answer those for you immediately (because I need to research the answers a bit more), but I’m going to submit them for future articles. They’re important topics and exactly the sort of answers we want to provide. Thanks for pushing us to provide more.
Paul,
Thanks for taking the time to share this. I’m not qualified to comment on the merits of this solution, but I’m going to bring it up at our next PV boot camp and see what Ken and some of the more experienced installers in the class think. If I get any ground-breaking feedback I’ll pass it along.
Brian
This is a terrific primer on solar roof possibilities…one thing that was not mentioned is how many hours of non-shaded sun light is needed to make it worthwhile…most roofs are of course slanted and won’t provide a “full day” of sunshine (my house for example is situated linearly from north to south and wouldn’t have a full day of sun on both sides…it would be great to know the number of hours needed for energy production that would power a house’s needs.
KC,
I think you’re asking a really natural follow-up question: “If my house is neither perfect nor terrible for solar, how do I know if it’s good enough?” It’s a hugely important question for anyone selling solar to be able to answer. And they have to be able to answer it quickly if they want to stay profitable doing residential installations. I don’t have an easy answer, but it does make me think about an article we’re planning for next week, “The High Cost of a Free Solar Estimate”. The article touches on this issue you’re raising – how it takes a lot of effort to do a really good site assessment and proposal, but the market is making it tough for installers to get paid for it.
Sorry I don’t have a great answer for you, but thanks for contributing to the conversation.
A word for the wise, before quoting any solar installation. Check with your local jurisdiction on ordinances that determine how you can install solar on specific properties. Many towns have strange rules in which you must follow to install photovoltaic panels on such properties .It might change the way you quote a project tremdously, which will eat into your profit margin at the end of these projects. SITE SURVEYS ARE IMPORTANT, BUT DON’T LEAVE OUT CHECKING WITH THE TOWNS FIRST BEFORE YOU SUBMIT YOUR QUOTE.
Dominic,
This is a really great point – thanks for sharing it. I remember hearing all your stories about the permitting process while eating lunch in that box car. The story about the guy who wired his entire house with extension cords really stuck with me for some reason. Anyway, thanks again for this important piece of advice.
Mr. Brian Hayden, i’am retired and looking at installing geo-therm systems in our operation. Several pre-existing homes and bldgs. Questions: living in North-East Texas- Are there a web site i can go to that shows the different options of vertical systems? i do own drilling equiptment/back hoes/pumps and etc. i think it might be attractive investment after i’am leave the family buis. after reading and reading i’am more confused at what a lot of people have to say about why their way is the BEST for my operations. would like to see some physical plans of different optons. How ever i’am leaning toward a close loop systems. please use my e-mail address
Yes, hearing a lot of conflicting information can be frustrating. I suggest starting with Kevin Rafferty’s ‘Geothermal Survival Kit’ – if you have more questions after that, feel free to call or email any time.
I also sent a copy to your email address!
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