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Rail vs. Rail-less: Which is the Best Solar Mounting Platform

Rail vs. Rail-less: Which is the Best Solar Mounting Platform Blog Feature
Posted by Kelli Fields on Jul 7, 2021 1:30:38 PM

If you’re thinking of putting solar PV on your metal roof to generate renewable energy and save money over time, you’ve made a great choice. Metal roofs are an ideal platform for mounting solar modules thanks to their long service life and durability. Solar arrays have a service life of 35+ years, and metal roofing has a demonstrated service life of 60 years. Aside from metal, there are no other roof types that measure up to that without requiring replacement. Both standing seam and exposed-fastened metal roofs support solar arrays very effectively.

graphic of conversation bubbles for questions and answersThere are two main approaches to attach solar modules: one uses rails; the other is rail-less. For railed installations, metal rails are secured to the roof and solar modules are attached to the rails to hold them in place. Rail-less systems attach components directly to the roof to support the solar modules. Each has its own unique aspects.


Let’s look at some pros and cons regarding roof considerations, aspects of layout and cost.


Roof Considerations

blog question graphic how are solar modules secured in place on standing seam or exposed fastened metal roof types

A: Rail: Rails mount to standing seam metal roofs via non-penetrating clamps. EF has two options: brackets can attach to the roof panel’s rib only, or brackets may attach in the roof panel’s valley and into the structure when preferred.

A: Rail-less: Rail-less solutions use the roof’s structural seams or ribs as the rails. The seams on standing seam roofs become the rails. EF trapezoidal ribs or corrugations are also structural elements of the roof design and can be used as rails. This offers greater flexibility in module placement because they completely cover the roof from end to end on 6- to 12-inch spacings.

photo of the S-5! PVKIT 1.0

Example of modules mounted on a standing seam metal roof using rail-less solar mounting

(Product shown: S-5! PVKIT®)


blog question graphic does the weight of your solar pv mounting system matter

A: Rail: The weight of the system can make a difference. Clamps and rails are ~ 19 lbs./kilowatt peak (kWp). Most new metal roofs can support the weight.

A: Rail-less: Rail-less is <3 lbs./kWp, which equates to approximately 85% lower added dead load. Lower added load is extremely helpful as an existing building may not have been designed to carry much additional weight. Rail-less also offers 25% better load distribution onto the roof and into the structure.


aerial photo of the Boulder Calcaire house with solar PVKIT

Rail-less based solar mounted system


blog question graphic are there obstacles on your roof for skylights HVAC equipment vents hips valleys or dormers

A: Rail: Rails will likely need to be field-cut to work around obstructions and architectural elements.

A: Rail-less: Rail-less solutions easily adjust to avoid obstacles and can be used in smaller areas where cutting rails to fit properly is time-consuming and unsightly.



blog question graphic is there a difference in how the solar modules are oriented

A: Rail: Rails are laid out across the ribs or seams (East-West), resulting in a portrait module orientation – 90 degrees to the rails.

photo of Australian railed solar PV

Rail-based solar mounted system


A: Rail-less: Because standing seams or exposed-fastened ribs are the rails and run in a North-South direction, modules are installed in landscape orientation – still 90 degrees to the roof’s inherent “rails.”

solar mounting built in rails

The standing seams or exposed-fastened ribs of a metal roof offer built-in rails for the attachment of solar modules.

solar panel color illustration portrait and landscape orientation with PV rail attachment


While we’re on the topic of laying out your solar PV array, planning wire management is also an important issue. Check out our latest video on Best Wire Management Practices in Railed and Rail-less Solar PV.


blog question graphic do you need to tilt your panels

A: Rail: If you have a relatively flat roof and want to tilt the array to capture the sun’s best angle, tilting is possible.

A: Rail-less: Tilting is not possible.

photo of protea bracket for solar pv system mounted using tilted rails

Example of a solar PV system mounted using tilted rails

(Product shown: S-5! ProteaBracket™)


Need help finding the right bracket for your upcoming solar mounting project?

Tell us about your project and we'll guide you to the best fit product for your specific roof panel.


blog question graphic how much do you want to spend on installation

A: Rail: Rails and components require time for layout, assembly, labor and installation. color graphic of a stopwatch

A: Rail-less: Pre-assembled rail-less systems require only about 90 seconds per module to install once you get the hang of it.


color graphic of stopwatch with CTA button less-time equals less money


blog question graphic how many parts are required

A: Rail: Traditional rail systems generally require nine to 12 components for a solar PV array.

A: Rail-less: State-of-the-art, rail-less systems can consist of no more than three components and save up to 35% or more on material costs.



blog question graphic will you need to ship materials

A: Rail: Rail systems require heavy components – and many more of them than rail-less. Using the example of a 50-kilowatt (kW) system, rail mounting would clock in at about 970 pounds, which means you pay the weight-calculated commercial freight charges.

A: Rail-less: Fewer materials and much lighter components average 149 pounds for the same 50 kW system as above—15% the weight of rail mounting.


rail mounted solar system a Lumina Solar MD 15

Rail-mounted solar system


Ideas to Hold Onto

Rail and rail-less solar PV array mounting solutions each have their pros and cons. Today, we covered just a few ideas on roof considerations, aspects of layout and cost to give you an idea of the differences.


No matter which attachment method you choose, we have proven solutions to meet your needs.


yellow and black graphic of the word versus

Still weighing rail vs. rail-less? Get the checklist to walk you through the multiple factors and help make an informed decision.


If you have specific questions, we’re always here to help. Simply comment below or contact us at

Tags: metal roof, metal roof clamps, solar mounting, metal roof brackets, standing seam metal roof, rail mounted solar panels, rooftop equipment, exposed fastened, cost, installation

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