Last updated on November 19th, 2019
How do you know if your roof can support solar panels? Let’s evaluate our solar panel roof load calculator.
Solar Panel Roof Load Calculator: Will My Roof Support Solar Panels?
Everyone is looking for sustainable and cheaper energy sources thanks to the ever-rising prices of fossil fuels.
A majority of people have decided to go solar to reduce their dependence on the grid power and become decarbonized. Use solar on your roof is a great way to generate power completely behind the meter.
Having a roof to place the solar panels is a crucial prerequisite for the PV system installation process.
But most people wonder, will my roof support solar panels? A solar panel roof load calculator helps you to establish the size and the weight of the solar panels that your roof can accommodate.
When you want to install solar panels, it is vital to understand certain features of the roof and the solar panels.
Solar panels differ in weights and sizes depending on the manufacturer and the brand. It is essential to determine whether your rooftop can support the solar panels before you plan a photovoltaic installation.
In this article, we will look at some of the core factors that determine whether a roof can support the PV system.
The solar panel roof load calculator is crucial when you want to establish the size and the weight of the solar panels that your roof can support.
You can download our free solar ROI calculator to use in Microsoft Excel or Google Sheets. This will help you see how roof load can affect the return on investment and payback for investing in solar.
It only takes 5 seconds to download.
Factors to Consider for Installing Solar Panels on Your Roof
There are a number of different considerations to factor for installing solar panels on your roof. You need to know them from the roofing perspective as well as the solar panel perspective.
Here are some factors that determine if your roof can accommodate the solar panels.
The first thing to consider when installing the solar panels is the roof. There are some aspects to consider when preparing your roof for solar panels.
The three main elements of the roof that you need to check are the roof structure, the roofing material and the age of the roof.
The Roofing Structure
The roof structure must be able to withstand the weights and the size of the solar panel. One feature to consider is whether your roof is flat or sloped. You need to check whether the roof is suitable for placing panels depending on the shape of the roof.
It is vital to carefully examine the roof structure to understand whether it can withstand the size and weight of the solar panel as well as of the mounting systems. A roof structural analysis is essential before the solar panels installation process commences.
Solar panel contractors may not be roofing experts and may not confirm whether your roof is sound structure-wise. But you can always consult a professional photovoltaic contractor or a structural engineer who will help you determine if your rooftop can support solar panels.
However, despite the kind of roofing you have, it is essential to understand that there are solutions for all types of roof types. You can create some roof reinforcement for solar panels. Some specialized pieces of equipment are used to install panels, and thus the structure of the roof doesn’t matter.
The installers can also find a way to improvise and can use racks to adjust the orientation and the angle of the solar panels. You can also opt for solar shingles if your roof is sloped. However, an electrician must set up the inverter box if you choose this style.
The Age of the Roof
Another vital factor is the age of your roofing structure. A majority of solar panels have a lifespan of around 25 years, and thus your roof must have the capacity to withstand that weight for those years.
If the roof is almost at the end of its life, then you may first need to do roof reinforcement, replacement or repair before installation of the PV system.
If you plan to make alterations after installation, you may end up spending more money than if changes are made before installation since you will need to remove the PV system first.
The Roofing Material
Another consideration to make is the material used on your roof. Different materials require different levels of care.
For example, if the roof is made up of slate tiles, then installers need to be extra careful when handling the roof so as not to damage it.
Different materials have different capacities of supporting solar panels. Concrete tiles may be of high material weight, but they can typically support high loads and are also considered to be more durable than other materials. Metal weights have a high strength to weight ratio and can withstand the weight of solar panels.
Asbestos or plastic roofs, on the other hand, are lightweight and activities that involve drilling could make a significant impact on their load-bearing capacity.
Structural engineers use the solar panel roof load calculator to come up with the correct load capacity of the roof material.
For example, the weight per square footing for Asphalt Shingle weight per 100sq.ft (lbs.) range is 190-250; the weight per 100sq.ft (kg) range is 85-110. A majority of roofs can withstand the weight of solar panels. Some crystalline panels, however, bear too much weight for some roofs to withstand.
In such an instance, you can opt for thin-film cells since they weigh less though it means a reduction in efficiency. Flat roofing will have a different profile than slanted.
If you are wondering if solar panels can damage your roof, then it is necessary to understand that they can help protect your roof from aging and weathering.
However, the installers must take special care when mounting the PV systems and the racks on your roof. They can use weather protecting agents, sealants, and metal flashing to protect the roof.
If the roof is flat, the panels and the racks can even be installed without mounting them directly to your roof. Instead, they can opt for heavy concrete blocks to keep the panels in place.
The solar panels can, however, affect the warranty of the roof since roofing companies don’t want you to install anything on your roof since it can increase the risk of roof leaks.
But, you can also find installers who offer their warranty through a third party roofing company.
See Related: Best Portable Solar Panels for Camping
Ordering solar supply is relatively straightforward. Before PV installation, it is essential to consider both the weight and the length of the solar panels:
The Weight of the Solar Panels
The weight of the PV module and the mounting structures plays a considerable role when planning a solar panel installation. Weight is a significant factor that can help determine whether a rooftop can handle a solar panel installation. A majority of the residential PV modules weigh around 40 pounds each, but it can range between 33 pounds to 50 pounds, depending on the manufacturer.
Commercial PV panels are heavier than residential panels, and most of them weigh over 50 pounds. When considering the weight based on a wattage level, a 250-watt crystalline panel weighs around 20Kg.
You need to reduce the distributed solar panels’ weight on the rooftop.
To achieve that the point load for the different fastening/mounting locations must be distributed in a manner that reduces the overall roof load, and it minimizes roof leaks. However, there must be a lot of optimization due to large point loads. The weight load of the PV system is vital to determine if your rooftop has adequate structural support for PV panels.
Both the mounting equipment and the solar panels weigh 2-4 lbs per square foot which is equivalent to 10-20 kg per square meter on average.
The weight is within the acceptable limits of any roof. The point loads are other considerations to take into account since installers often want to minimize the number of mounting locations for them to reduce the risk of leakages.
According to EnergySage, the total weight load of the average PV system including all the hardware components, the PV modules, and mounting racks is about 3 to 4 pounds per square foot.
A majority of both residential and commercial roofs are designed in a way that they can handle at least 20 pounds per square foot. Some older roofs or those that have sustained prior damage may not have the capacity or structural support for PV systems.
The Length of the Solar Panels
It is vital to consider the length of the PV systems along with other mounting pieces of equipment. Residential and commercial PV panels differ in sizes which are based upon the purpose.
The residential PV modules measure about 5.4 feet by 3.25 feet or 65 inches by 39 inches, and each module usually holds around 60 solar cells. The commercial PV modules, on the other hand, are a bit larger and the standard model’s length is about 6.5 feet by 3.25 feet or 78 inches by 39 inches.
The commercial photovoltaic panels hold around 72 cells. Smaller PV panels can maximize space on the rooftops of the residential homes whereas the larger commercial PV panels are fit for commercial projects despite being large.
These are some of the best solar panels for your roof.
Use our solar panel lifespan guide to determine how long your solar panels will last.
Conclusion on Solar Panel Roof Load Calculator
I hope this solar panel roof load calculator guide will help you understand whether your roof can support solar panels. It is vital to remember that just because a roof can support a photovoltaic system doesn’t mean rooftop placement is your ideal option.
Some roofs don’t have sufficient space to place a PV system and for a PV array. For example, some have shading issues that can significantly reduce solar output.
In such cases, you can opt for other options like you can go for ground-mounted PV systems. You can go completely off the grid if you opt for solar plus storage.
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