Is my roof suitable for solar panels (and what is the weight of a solar panel)?

If you’re just starting to think about installing solar panels for your home, then you may be wondering if your roof is suitable? Flat or sloped, there are solutions for just about any roof type (using Sunmetrix Discover, you can adjust the slope and see the impact). However, there are some important considerations before you make the leap to solar energy.

How old is your roof?

If your roof is nearing the end of its life, it makes more sense to repair or replace your roof first. Making changes to your roof after solar panels have been installed is more expensive, as they will have to be removed first. If you’re a few years away from a roof replacement, why not consider combining your solar panel installation with your new roof? Some roofing companies are getting into the solar energy business, simplifying the whole process for you.

What type of roof do you have?

Unless your roof has a very steep slope, which may require specialized equipment to install your panels, it doesn’t matter whether your rooftop is flat or sloped. Installers will account for the slope (or lack of slope) of your roof and determine whether you need racks to adjust the angle and orientation of the panels.

The material used on your roof is another consideration. If your roof is covered with slate tiles or another specialized material, the installation of your panels will be more expensive as the installers will have to take more care not to damage your tiles.

Will the installation of solar panels damage my roof?

Solar panels can actually help in protecting your roof from weathering and aging. However, you may be wondering if the way in which the panels are installed can cause damage, leading to leaks or other problems? The installers take special care when mounting the racks and panels on your roof, using sealants, weather protecting agents and metal flashing to protect your roof. On a flat roof, the racks and panels can even be installed without mounting them directly to your roof. Instead, very heavy concrete blocks may be sufficient for keeping your panels in place.

Will the installation of solar panels affect my roof warranty?

The answer is often yes, as many roofing companies do not want you to install anything on your roof which could increase the risk of leaks. However, many installers are providing their own warranty, sometimes through a third party roofing company, which takes the worry out of the equation.

How heavy are solar panels?

This is a common question! On average, solar panels and the mounting equipment weigh 2-4 lbs per square foot (10-20 kg per square meter), which is usually within the acceptable limits of your roof. However, one has to take into account the point loads, as installers often want to minimize the number of mounting locations in order to minimize the risk of leaks. If the installer does not distribute the weight optimally, the point loads can be considerable.

Are solar shingles an option?

If you have a sloped roof, you can consider solar shingles, which are designed to integrate with conventional asphalt roof shingles. Originally much more expensive than traditional solar panels, solar shingles have come down in price, making them an especially attractive option for someone already re-shingling their roof. They can be installed by a regular roofer, as they are relatively simple to install. However, an electrician is needed to set up the inverter box.

10 Replies to “Is my roof suitable for solar panels (and what is the weight of a solar panel)?”

  1. Hi, Our company is now into new and renewable energy. i have some doubt about the the installation of panel on to the roof (Aluminium Sheet Roofing) and to the concrete roof. please help to calculate the weight and how much area will take. awaiting your reply

    1. Thank you for your question. Without knowing your power needs, it’s not possible for me to give you specific information regarding the size of system required. However, we have a calculator that can help you assess the size of system that will meet your needs, and is location specific – just enter your postal code and play around with the various sliders to see the effect: http://sunmetrix.com/discover.

      Also, we have another article “Solar Panel Size for Residential, Commercial and Portable Applications” that you might find helpful: http://sunmetrix.com/solar-panel-size-for-residential-commercial-and-portable-applications/

      Hope that helps!

  2. I have a flat roof without a basement. The roofing material is a membrane. Is it still possible to mount racks on a roof with a membrane? Racks would be required to angle the solar pv because it slopes slightly downward, facing north.

    1. That’s a good question – one of the great things about a flat roof is that the panels can be oriented in which ever way maximizes your production (usually, south-facing if you are in the northern hemisphere, or north-facing if you are in the southern hemisphere). Moreover, as mentioned in the article, sometimes the panels can be mounted without piercing the membrane roof, using concrete blocks to weigh them down. Ultimately though, you need to check the fine-print of the warranty that came with your membrane roof. However, as we also mention in the article, often the solar installers themselves or another third party offer a warranty with the installation to protect you in the event of a leak. The best course of action would be talk with installers in your area and see what they suggest. We would be happy to help put you in touch with some if you like. Just go to http://sunmetrix.com/solar-installer-reviews/ and enter your zip/postal code to see a list of installers in your area, along with reviews.

  3. Thank you for your question about solar panels for a travel trailer. Since the available space is much smaller and because the electricity requirements are considerably less than for a full-size home, the size of solar PV system that you would need would generally be quite a bit smaller (and therefore lighter). In our article about solar panels for RVs (http://sunmetrix.com/rv-solar-panels-soaking-up-the-suns-rays-while-on-the-move/), we discuss this in more detail, but most often people opt for a solar kit that comes with the panels, inverter, batteries, and charge controllers, on the order of 100-300 watts, which should be enough to power lights, small television, and small appliances. With a back-up generator for nighttime or cloudy days, you should be all set!

  4. Hi Simone, would i need lighter weight panels for a steel shed roof? I use it as a art studio and sometimes stay over night, so usage is not the same as for a normal home. Also can you recommend the size system I would need.

    1. Hi Judith, Thank you for your question. It’s hard for me to recommend a system size without knowing your average electricity use or your location (since the amount of electricity your panels can produce is location specific), but we have a tool that may be useful for you: Discover (http://sunmetrix.com/discover). Just enter your zip code and adjust the electricity consumption slider to get some estimates. Obviously, the less electricity you use, the smaller (and lighter) the PV system will to be. It’s important to note that the orientation of your roof and the level of shade will greatly impact the viability of installing a solar PV system (in the northern hemisphere, a south-facing roof is ideal). For more on shade, we have another article that may be helpful: http://sunmetrix.com/trees-and-shade-how-will-they-affect-my-solar-panels/. An installer will be able to help you determine whether a solar PV system makes sense for you and will help you determine the ideal system size as well. Moreover, he/she should assess the structural integrity of your roof, and its suitability for mounting panels. If you need any help finding installers in your area, we’re happy to help!

  5. Hi Simone,
    After having solar panels installed we have noticed cracks appearing all over our house. The structural engineers who came to look at it all said it is not due to settling as our house was built in the early 1900s. We have a vaulted ceiling in our upstairs bedroom with an acute slope and no attic- only small knee walls. It is on this acutely sloped roof that the panels were installed. Additionally, one of the doors in the upstairs bedroom (under the vaulted ceiling where the panels are) is getting stuck in its frame and now we cannot close the door. The cracking has occurred in almost every room of the house but most severely upstairs under the vaulted roof where the panels were put. One guy from the solar company told us it could be due to the wind getting up under the panels and shifting the house just enough to cause cracking. I have also read it could be due to the rafters spreading due to the added weight. What are your thoughts on this? Could the company have miscalculated the weight? Or the way the wind hits our roof? Thank you!

    best,
    Bea

    1. Hi Bea, I’m sorry to hear about the problems you experienced since installing solar panels on your roof. Fortunately, this type of cracking is not commonly experienced by homeowners. A structural engineer is the best person to consult, as you did already to be sure it was not a settling issue. Wind could be a problem in some situations, so this would be a possibility worth investigating further. Reputable and well-trained solar installers (such as with a NABCEP certification) should be able to assess the viability of your roof when it comes to it’s configuration and condition, as well as the weight of the panels, but again diagnosing your specific problem is best left to an expert such as a structural engineer. I wish you the best with resolving this unfortunate outcome.

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