Roof mount vs ground mount solar is a trade-off between using space you already have and getting the ideal angle. Most US homes go on the roof because it’s cheaper and out of the way. A ground mount can make more energy per panel and avoids roof penetrations, but it needs land and trenching.
Electrical work can be dangerous: follow the manual, fuse and size every cable correctly, and use a licensed electrician for anything connected to household wiring.
Roof Mount vs Ground Mount Solar at a Glance
| Roof mount | Ground mount | |
|---|---|---|
| Upfront cost | Usually lower | Usually higher (footings, steel, trenching) |
| Tilt and direction | Limited to roof | Can be set to the ideal angle |
| Cooling | Less airflow | Better airflow, slightly higher output |
| Roof risk | Penetrations; must remove for re-roof | None |
| Space | Uses existing roof | Needs open, unshaded yard |
| Cleaning and snow | Harder to reach | Easy |
| Permits | Standard | May need zoning, setbacks, trench inspection |
Cost Differences
Ground mounts add concrete or driven-pile footings, more steel, and a buried conduit run back to the house. That typically raises cost per watt compared with a simple roof install, though prices vary by site. Get both priced if you have the room.
Output Differences
A ground mount can face due south at the best tilt for your latitude. NREL’s PVWatts lets you model both: enter your roof’s tilt and azimuth, then the ideal values, and compare annual kWh. On a well-oriented roof the difference may be small; on an east-west or flat roof it can be bigger.
Roof Risk
Every roof mount means attachments through the roofing. Quality flashing and a good installer make leaks rare, but plan ahead:
- If your roof has less than about 10 years left, replace it first
- Removal and reinstall for a future re-roof costs extra
- Check what the installer’s workmanship warranty covers
When a Ground Mount Makes Sense
- Shaded, small or complex roof
- Old roof or historic home
- Plenty of open land within a reasonable trench distance
- You want easy access for cleaning and snow removal
Worked Example: Comparing Output With PVWatts
To see how much a ground mount’s better angle is worth at your site, run PVWatts twice with the same system size:
| Run | Tilt | Azimuth | What to enter |
|---|---|---|---|
| Roof | Your roof pitch in degrees (6/ | Direction the roof faces | Array type: fixed roof mount |
| Ground | Near your latitude, or the tilt PVWatts suggests | 180° (south) | Array type: fixed open rack |
The open-rack option models better airflow behind the panels. Then compare yearly kWh. Here’s an illustrative result for a 7 kW system:
| Case | Yearly kWh (example) | Difference |
|---|---|---|
| South roof, 6/ | 9,800 | baseline |
| East-west roof split | 8,600 | −12% |
| Ground mount, south, ideal tilt | 10,100 | +3% |
On a good south roof the gain from a ground mount is small. On an east-west, shaded or flat roof, the gain is bigger. Your own PVWatts runs decide it.
Worked Example: Trench Distance and Wire Size
Long runs from a ground mount to the house add cost for trenching, conduit and larger wire to limit voltage drop. Using the voltage drop formula for a 240 V circuit (two-way length):
Voltage drop = 2 × length (ft) × current (A) × resistance (ohms per 1,000 ft) ÷ 1,000
For a 7.6 kW inverter output at 240 V (about 32 A), 150 feet from the panel:
| Wire (copper) | Resistance per 1,000 ft (approx., NEC Ch. 9 Table 8) | Drop | % of 240 V |
|---|---|---|---|
| 8 AWG | 0.778 Ω | 2 × 150 × 32 × 0.778 ÷ 1,000 = 7.5 V | 3.1% |
| 6 AWG | 0.491 Ω | 4.7 V | 2.0% |
| 4 AWG | 0.308 Ω | 3.0 V | 1.2% |
Many designers aim for 2% or less on solar circuits. Longer runs push you to bigger wire. Learn more in voltage drop calculation and the wire gauge chart.
Ground Mount Foundation Types
| Type | How it works | Good for |
|---|---|---|
| Concrete piers | Posts set in poured concrete footings | Most soils |
| Driven piles | Steel posts driven by machine | Larger arrays, suitable soil |
| Helical piles | Screw-in steel anchors | Rocky or variable soil, fast install |
| Ballasted | Weighted base, no digging | Where digging isn’t allowed |
Footing depth often depends on local frost line and soil, and the engineering for wind and snow loads. For a DIY approach, see DIY ground mount solar array.
Step-by-Step: Deciding Roof vs Ground
- Check roof age and condition. A roof near the end of its life points to replacement first, or a ground mount.
- Model both in PVWatts as above.
- Measure the yard: unshaded open area, distance to the main panel, setbacks from property lines.
- Check zoning and HOA rules for ground-mounted structures.
- Get both priced by the same installer for a fair comparison.
- Compare price per estimated kWh, not just per watt. See how much do solar panels cost.
Rapid Shutdown and Ground Mounts
NEC 690.12 rapid shutdown rules apply to PV systems on or in buildings. A ground-mounted array that’s not on a building often isn’t subject to the same module-level requirement, which can affect inverter choice. Your AHJ decides how the rule applies. See microinverters vs string inverters and solar panels on roof fire safety.
Snow, Cleaning and Access
Ground mounts are easy to reach for brushing snow or cleaning. Steeper tilts also shed snow faster. Roof arrays need ladders or professionals. Whether cleaning is worth it at all is covered in solar panel cleaning.
FAQ
Is ground mount solar more efficient?
Often a bit, thanks to ideal tilt and cooler panels, but site matters more.
How far can a ground mount be from the house?
It depends on wire size and voltage drop. Longer runs cost more in wire and trenching.
Do ground mounts need permits?
Yes, usually building and electrical, and sometimes zoning.
How much more does a ground mount cost than a roof mount?
It depends on soil, trench length and array size. Ask an installer to price both on the same quote.
Can a ground mount use bifacial panels?
Yes. Ground mounts with space under the panels can use bifacial panels, which collect some reflected light from the back side. The gain depends on height and ground surface.
What tilt is best for a ground mount?
A tilt near your latitude is a common starting point for maximum yearly output. PVWatts lets you test different tilts at your address and see the yearly kWh for each.
Does a ground mount need a separate permit?
Usually it’s covered by the solar building and electrical permits, but zoning setbacks, structural review and trench inspection may apply. Check with your AHJ.
Sources: NREL PVWatts; NREL Solar program; NFPA 70 (NEC) 2023 Articles 300 and 690; NFPA 70 (NEC) Chapter 9 Table 8 and 690.12. Accessed Oct 2026.
Related: Adjustable Solar Panel Mounting Brackets Review, CleanTite Solar Panel Cleaner Review