Ground mount vs roof mount solar: which one fits your property?

The short answer: what each mount trades

Neither mount is the upgrade. Each one converts a different asset into production: the roof mount converts a structure you already paid for (on clay or concrete tile, at a mounting premium the tile roof guide prices per watt), and the ground mount converts land, trenching, and racking steel. The right choice is the one whose costs land on the asset you have more of. A sound, well-oriented roof with no shade is hard to beat on price, because the mounting surface is free. A shaded, cut-up, or worn-out roof flips the answer, because no panel efficiency survives a bad roof plane, and the ground array can be pointed exactly where the roof cannot.

Work through the table before any quote arrives. It is the whole decision in one screen: if your situation fails a roof row, the ground column is where the fix lives, and if it passes every roof row, a ground quote has to justify itself on production alone.

When the roof says no

The Department of Energy's step-by-step guide for consumers puts roof suitability second, right after choosing an installer: a solar installer, roofing expert, or structural engineer can help you determine your roof's solar suitability, and it helps to know when the roof was installed or replaced. If you do not know and the previous owner cannot tell you, your local government usually holds the building permit record. That record matters more than any satellite estimate, because a roof in the last third of its life is a common reason the roof mount loses: panels are a 25 to 30 year commitment, and mounting them over roofing that needs replacement in year eight buys a removal and reinstallation bill in the middle of the system's life.

Condition is only one of three ways a roof can say no. Direction is the second: the Department of Energy's siting guidance for home systems notes that modules produce best facing true south in the northern hemisphere, and that facing up to 45 degrees east or west of south does not significantly decrease performance. A roof whose planes face north, or fragment into small dormered sections, starts far enough behind that a well-sited ground array can out-produce it with the same panels. Shade is the third: a roof plane shaded by trees you cannot or will not remove has a production ceiling no equipment choice lifts (the shade pricing guide explains why), while open ground elsewhere on the property may sit in full sun.

None of these verdicts is yours to guess at. A proper site assessment measures all three, and an installer who quotes a roof price without asking the roof's age or checking its planes is skipping the step the Department of Energy puts second. Get the roof verdict in writing, with the reason. That document is what makes the ground-mount comparison a real comparison instead of an upsell.

What ground mounting buys you

The ground array's real product is control. Tilt can be set near the site's latitude, which the Department of Energy's siting guidance treats as the general optimum, instead of accepting whatever pitch the roof happened to be built at. Direction can be set to true south regardless of how the house sits on its lot. Rows can be spaced so no panel shades the next, and the array can be placed in the one part of the property the trees do not reach. On a property where the roof fails on direction or shade, that control is worth real kilowatt-hours, and it shows up in exactly one place in the worksheet: the production estimate, which is why the estimate's inputs deserve the same scrutiny whichever mount you choose.

The second purchase is separation from the roof. A ground array makes no penetrations, carries no load on the rafters, and never has to come down for a re-roof. On a HUD-code manufactured home, whose roof was built to a 20, 30 or 40 psf zone load and where a roof array needs a state alteration permit, that separation often decides the question, as the manufactured home solar guide works through. Roof work stays roof work: when the shingles reach end of life, the roofer works on an empty roof, and the array's production is not hostage to the roofing schedule. The third purchase is access. Every inspection, cleaning, and inverter check happens at ground level, which makes the routine upkeep in the maintenance guide cheaper to do and easier to keep up, and makes snow clearing a choice rather than a roof climb.

Hold the enthusiasm to one test, though. Control is only worth what it produces or what it avoids. If the roof is sound, south-facing, and unshaded, the ground array's control buys almost nothing the roof was not already giving you, and its site work is pure premium. The worksheet section below is how you make the ground quote prove its number instead of its story.

Between the two mounts sits a small family of hybrids worth one question at the site visit. The Department of Energy's consumer guide notes that where a south-facing roof is unavailable, some owners mount on a garage roof or build the array as an awning or porch cover, and ground arrays themselves come in fixed and tracking forms, the tracking mount following the sun across the day. For a house, the fixed ground mount is the standard comparison in this page; a tracking proposal has to justify its moving parts and its premium inside the production estimate, in writing, the same way any ground quote does. Ask about these only if the two main mounts both fail on your property, because each hybrid reopens the permit and pricing questions the main comparison settles.

What a wrong-facing roof costs, modelled for one city

The usual case for a ground mount is that it can face the right way when the roof cannot. The federal guidance on direction comes in two generations. The Department of Energy and NREL consumer guide Own Your Power (2009) said a southeast- or southwest-facing system performs about 5 percent below a south-facing one, and that eastern, western, and northern exposures are not recommended. The Department of Energy's Energy Saver guidance, read here from an archived December 2017 capture, put it more loosely: modules can face up to 45 degrees east or west of true south without significantly decreasing performance. Neither puts a number on a roof facing due east or due west, which is exactly the roof that sends people looking at their yard.

So this guide modelled it for one city. On October 28, 2026 we ran a 1 kW system through PVWatts version 8 for Seattle, on a fixed roof mount at a 20 degree pitch, three times: facing south, due east and due west. Everything else stayed fixed: a standard module, 14 percent total losses, a DC to AC ratio of 1.2, 96 percent inverter efficiency and typical-year weather. The south-facing roof modelled 1,088 kWh per kW a year, the east-facing roof 912 and the west-facing roof 943. In other words, the east roof produced about 84 percent of the south roof and the west roof about 87 percent.

Two readings follow. First, a roof facing due east or due west, twice as far off south as the 45 degree range Energy Saver called harmless, lost 13 to 16 percent in this run. That is a real loss, but at this modest pitch it is not the disqualification the 2009 guide implied, and it sets the bar a ground quote has to clear. On an 8 kW array, the gap is about 1,406 kWh a year against the east roof and 1,161 against the west roof. Own Your Power notes that a ground- or pole-mounted system can be installed with the same orientation and tilt as a roof-mounted system, so this guide treats a south-facing ground array at the same 20 degree tilt as the south-roof case (an open-rack ground layout, which PVWatts models differently, was not run): the gap above is roughly what a ground array can win back on a property whose only roof faces east or west.

Second, that gap is the whole budget the ground premium has to fit inside. Divide the ground quote's extra cost by the extra kilowatt-hours it recovers each year, multiplied by the years you expect to own the system, and you have the price you are paying per recovered kilowatt-hour; set it against what that energy is worth under your utility's tariff, which the net metering guide explains. Seattle is one climate, and this run did not model a north-facing roof, a steeper pitch or a ground array at a different tilt, so treat the numbers as the shape of the answer, not your answer. Run your own address in the free PVWatts web calculator with your roof's real pitch and azimuth beside a south-facing ground layout, and bring both runs to the quote conversation.

Energy Saver made the matching point from the price side: a bid for a system mounted on the ground is usually very different from another bid for a rooftop system. That difference is not a reason to distrust either bid. It is a reason to ask both installers for the same system size and the same production inputs, so that the only things left to compare are the mount, the site work and the modelled energy, which is exactly what the worksheet section below does with two quotes for one house.

What ground mounting costs you

A ground quote carries lines a roof quote never sees, and each one belongs on its own line of the contract so the comparison stays honest. Foundations and racking built to stand free in wind and frost cost more than rails bolted to rafters. The trench from the array to the house carries conduit, wire, and digging, and its price grows with every foot of distance and every obstacle in the path, which is why two ground quotes for the same property can separate by more than two roof quotes would. Longer wire runs are also a design input, not just a cost: your installer sizes the conductors for the distance, and that belongs in the design documents, not in a verbal assurance.

Land is the second cost, and it is permanent. The array's footprint, plus the setbacks your zoning rules require from property lines, leaves your yard for the life of the system. The Department of Energy's consumer guide plans on roughly 100 square feet of unshaded space per kilowatt as a sizing rule of thumb, so an 8 kW array asks for something like 800 square feet of your clearest ground before setbacks, paths, and row spacing. Read the site plan the way you would read a fence line: where exactly, how high at the low edge, and what still fits around it.

Permits are the third cost, usually in time rather than money. A ground array generally draws the same building and electrical permits as a roof system and adds zoning review for setbacks and, in some jurisdictions, fencing or screening conditions. None of this is a reason to avoid the ground mount. It is a reason the ground quote's site-work lines and permit path should be itemised before you compare its total against a roof quote's total. Insurance usually treats the two differently: on a standard homeowners policy a detached ground array typically falls under the other-structures limit and a rooftop array under the dwelling limit, as set out in the homeowners insurance guide.

How much yard a ground array takes, and how much load a roof array adds

The land question has a federal starting figure. Own Your Power planned on about 100 square feet of unshaded south-facing roof or yard space for every kilowatt, and up to 175 square feet per kilowatt for thin-film modules. Lawrence Berkeley National Laboratory's 2026 data update puts the median US residential system installed in 2025 at 7.7 kW, with most between roughly 5 and 12 kW. At the 2009 planning figure, those sizes ask for about 500, 770 and 1,200 square feet of module area, as the figure shows.

Treat those bars as a ceiling rather than a forecast. The same laboratory reports median module efficiency rising about 0.4 percentage points a year over the long term, so a modern module packs more watts into each square foot than the panels the 2009 figure was written for. Module area is also not the whole footprint. A ground array adds the space between rows, so that one row does not shade the next in winter, a path for mowing and inspection, and the setbacks your zoning code requires from property lines. Ask the installer for a scaled site plan that shows all four, because two layouts with the same panel count can claim very different shares of a yard depending on how the rows are spaced and how high the low edge sits.

The roof side of the ledger has its own physical cost. Own Your Power told homeowners to make sure the roof can hold the weight of the system, which it estimated at 3 to 5 pounds per square foot depending on the technology and installation method. On a sound roof, that is a load an engineer checks rather than a reason to avoid the roof. On an older structure, the structural review can become a line item, and that line belongs in the roof quote when you set it beside a ground quote. A ground array puts no load on the rafters at all, which is one more reason the comparison has to be made line by line rather than total against total.

Put the two halves of this section together and the land test is short. Measure the clear, unshaded ground you are willing to give up for the life of the system, subtract the setbacks, and compare what is left with the module area for the size your bills call for, plus room between rows. If the yard passes with space to spare, the ground quote is worth requesting. If it only passes by squeezing rows together or pushing against a property line, the site plan will show it, and the roof, even an east- or west-facing one, may be the better compromise.

Run both quotes through the same worksheet

The comparison only works in units, never in totals, and the units are the ones from the cost guide: gross price divided by watts for cost per watt, then net price divided by first-year kilowatt-hours for cost per unit of energy. Ask both installers for the same system size, the same unbundling, and a production estimate with its inputs shown for each mount. Where the two estimates differ, the difference should be traceable to orientation, tilt, and shade inputs, not to one modeller's optimism. The production estimate guide walks through how to read those inputs line by line.

The worked example below prices both mounts for one house so you can watch the two units separate. Notice what the ground quote has to prove: at equal production it is simply more expensive per watt and per kilowatt-hour, and it only closes the gap if its production estimate is genuinely higher for reasons you can see in the site plan. That is the honest shape of this decision. The ground mount wins on bad roofs and good land; it does not win by default.

One more line belongs in both quotes before any division: what each mount does to the roof budget. A roof quote on a roof with twenty or more good years left is close to complete as priced; with fifteen years left, a mid-life removal is likely, so ask for the detach-and-reinstall line in writing (the roof sequencing guide prices all three sequences). A roof quote on a roof with eight years left is missing a future removal and reinstallation, and that missing line, not the panels, is often what makes the ground quote the cheaper twenty-year decision. Price the sequence, not the snapshot.

The third option, when both mounts fail

Some properties fail both tests: the roof is wrong and the land is shaded, small, or unavailable. The Department of Energy's consumer guidance names the fallback directly: if your home is not suitable for rooftop solar, you can still get the benefits of clean energy through a community or shared solar program, where you subscribe to a share of a larger array built elsewhere. That is not a consolation prize. For a shaded lot it can be the only solar option whose production is real, and it carries no equipment, no roof interaction, and no 25-year commitment to a mount.

Treat a community solar subscription with the same contract discipline as any quote on this site: read the escalator, the term, and the exit clause before the savings claim. And if an installer responds to a failed roof and a failed yard by proposing to clear mature shade trees or mount on a roof the assessment already rejected, you have learned the most useful thing a site visit can teach you. The mounts are a property decision, not a sales target.

There is also a timing version of the third option: wait for the roof. If the roof fails on condition alone and a replacement is already in your five-year plan, the cheapest mount decision may be a calendar decision, replacing the roof first and mounting on it once, in the sequence the roof sequencing guide works through. A ground quote taken today is still useful in that plan, as the price of not waiting. Decisions like this are why the mount question belongs at the start of the project, before the first quote hardens around an assumption nobody examined.