Ground mount or roof mount, which is better?
Neither one wins everywhere.
A roof-mounted solar array makes use of space you already have and generally costs less per watt. A ground-mounted system gives you more control over orientation, tilt and placement, and it can be a great alternative when the roof is not suitable.
The right answer depends on your property.
Here is how we compare the options for Central Wisconsin homes, farms and businesses.
A roof mount is usually the stronger option when your roof has good sun exposure, is structurally sound, has plenty of remaining life and offers enough usable space for the system you need.
A ground mount may be the stronger option when the roof is heavily shaded, aging, unusually shaped, structurally limited or unable to accommodate the desired system size.
Ground-mounted solar can also provide more flexibility for orientation, tilt, snow management and future maintenance.
Ground-mounted solar requires additional materials and site work that rooftop systems do not.
Depending on the design, that can include:
Current national marketplace data show residential ground-mounted systems costing more per watt on average than rooftop systems.
That does not automatically mean a ground mount is a worse investment. If the ground location provides significantly better solar access, allows a larger system or avoids major roof work, the added cost may make sense.
It is also important to compare cost per watt and complete system designs, not just total project price. Ground-mounted systems are often larger than rooftop systems, which can make the total-dollar difference look greater.
A rooftop array has to work with the pitch, orientation and available space of the existing roof.
On the ground, we have more flexibility.
A ground-mounted array can often be oriented toward the south and installed at a tilt selected for the property and design goals. Better airflow around the modules can also help keep panels cooler during hot weather.
Ground mounts are also easier to access for inspection and snow management.
Some ground-mount racking systems allow seasonal tilt adjustment, using a steeper setting during fall and winter and a shallower setting during spring and summer.
The production benefit depends on the site and the angles involved, so seasonal adjustment alone usually is not the reason to choose a ground mount. The larger practical advantage in Wisconsin is often winter accessibility and improved snow shedding.
We explain the process in more detail here: How Seasonal Ground-Mount Tilt Adjustment Works.
Both rooftop and ground-mounted solar systems are designed to operate in snowy climates, but snow behaves differently on each.
Roof-mounted panels often shed snow once conditions allow, although where that snow lands should be considered during system design, especially around entrances, walkways and other frequently used areas.
Ground-mounted systems are easier to access if snow removal is desired. They can also be designed with additional clearance beneath the lowest edge of the array to help account for accumulated and drifting snow.
DOE guidance specifically recognizes higher tilt angles and adequate clearance as strategies for improving snow shedding and winter resilience.
Ground-mounted solar requires a foundation designed for the specific site.
For residential construction covered by Wisconsin's Uniform Dwelling Code, applicable foundations generally require frost protection to at least 48 inches below adjacent grade or below the frost-penetration level, whichever is deeper.
The exact foundation approach for a solar array depends on the project, soil conditions, structural loads and applicable code requirements.
Depending on the site and racking system, that may involve driven piles, ground screws or concrete foundations.
Soil, drainage, rocks, slope and groundwater conditions can all influence the design.
A ground mount needs enough open land with good solar exposure.
Local zoning and permitting requirements can also affect:
Those requirements vary by jurisdiction, so we review them as part of the design and permitting process.
The electricity produced by a ground-mounted array still has to reach your electrical equipment.
That means the distance between the array and the home, business or farm building matters.
An array located relatively close to the electrical service is a different project from one hundreds of feet away.
Longer runs can increase:
That is one reason two ground-mounted systems of the same size can have very different installed costs.
Before installing rooftop solar, we look at the condition and expected remaining life of the roof.
Solar panels are designed to operate for decades. If the roof underneath them is likely to need replacement relatively soon, it often makes sense to address the roofing first.
Otherwise, the solar array may have to be removed and reinstalled later so the roof can be replaced — adding unnecessary expense.
As a rule of thumb, if we believe a roof is approaching replacement, we would rather talk about that before installation than install a long-lived solar system over a short-lived roof.
Sometimes that leads to reroofing first.
Other times, it may make a ground-mounted system more attractive.
One of the biggest practical advantages of a ground-mounted system is access.
Inspection, service, vegetation management, snow removal and seasonal adjustments can all be performed from the ground.
That convenience comes with some added responsibilities. Vegetation has to be managed around the array, and the system may need protection from wildlife, landscaping equipment or other activity on the property.
Roof-mounted arrays stay out of the way and preserve yard space, but future service requires safe roof access.
During a solar site assessment, we evaluate the realistic locations available on the property.
That includes:
Then we model the practical options and compare complete designs.
The goal is not simply to identify where panels can go.
It is to determine which design makes the most sense over the life of the system.
Sometimes.
If a ground-mounted system provides much better solar access, allows the system size you actually need or avoids an unsuitable roof, the additional cost may be worthwhile.
If you already have a large, unshaded roof in good condition, rooftop solar will often be the more economical choice.
They can.
Ground-mounted systems provide more flexibility to optimize orientation and tilt, and they can be easier to keep clear of snow.
But the ground location still has to be good.
A well-oriented, unshaded rooftop system can outperform a ground-mounted array placed in a compromised location.
It depends on the system size, racking design and available solar access.
Residential systems do not necessarily require a large amount of acreage, but there must be enough open space for the array itself, proper setbacks and access for installation and maintenance.
We lay out the exact footprint during the design process.
Sometimes.
Slope affects foundation design, equipment access, drainage and construction.
A moderate south-facing slope may work very well, while steep, unstable or poorly drained terrain may make installation more difficult.
We evaluate the actual site before recommending a design.
A properly designed and installed rooftop solar system should not damage a sound roof.
Solar attachments and flashing are standard parts of rooftop PV installation. The specific attachment method depends on the roofing material, roof structure and mounting system.
If your roof is still under a manufacturer or contractor warranty, it is also worth reviewing the applicable warranty terms before installation.
The house roof and a traditional ground mount are not the only options.
Depending on the property, we may also consider:
Sometimes the best solar location is not the first one a property owner has in mind.
Ground mount versus roof mount is not a question with one universal answer.
A roof mount generally offers lower installed cost and makes use of existing space.
A ground mount offers greater flexibility in orientation, placement, access and system size.
The best choice depends on production, cost, roof condition, available land, snow, electrical infrastructure and your long-term plans for the property.
At Northwind Solar, we evaluate the property as a whole and compare the realistic options rather than assuming one mounting type is automatically better.
If both options make sense, we can model both and show you what the differences mean for your property.
Northwind Solar has been designing, installing, and servicing solar in Central Wisconsin since 2007. We are a worker-owned cooperative, our designers and installers are NABCEP-credentialed, and we back our work with a 10-year workmanship warranty.
Tell us about your site and we will model your actual production, show you the assumptions behind the numbers, and answer your questions with no obligation.
Request a free estimate | Call us at 715-630-6451