Short answer: on flat or gently sloping land with strong direct sun, a single-axis tracker usually wins: NREL found 12–25 % more energy than fixed-tilt across 50 US cities. Fixed-tilt is the better choice on steep, rocky or cyclone-exposed sites, where maintenance is hard to organise, or where capital is the binding constraint. Seasonally adjustable tilt sits in between: part of the gain, no motors.
The mounting structure is a small share of a plant’s cost, but it decides how much energy every module produces for 25 years or more. This guide sets out what the data says, where each option fits, and the questions to answer before you choose.
Key numbers
- 96 % of new utility-scale PV capacity built in the United States in 2023 used single-axis trackers, and 99 % of new projects in 2024 (Berkeley Lab, Utility-Scale Solar 2024 edition and 2025 update).
- Tracking raises the annual capacity factor by roughly 5 percentage points in sunny regions (Berkeley Lab).
- Single-axis trackers produced 12–25 % more energy than south-facing fixed systems at 25° tilt; the gain was largest in arid regions and smallest in humid, cloudy ones (Drury et al., NREL).
- Bifacial modules add a further 4–15 % on single-axis trackers (NREL, 2019).
- Terrain-following trackers accept around 15 % north–south slope (about 8.5°), according to manufacturers’ published data.
1. The three options
| Fixed-tilt | Seasonally adjustable | Single-axis tracker | |
|---|---|---|---|
| How it works | One tilt, set at installation | Rows re-tilted a few times a year | Rows rotate east–west through the day |
| Capital cost | Lowest | Low | Highest per kW in most markets |
| Energy yield | Baseline | Modest gain | 12–25 % above fixed (NREL) |
| Moving parts | None | Manual adjustment | Motors, controllers, sensors |
| Slope tolerance | Highest | High | Lower (about 15 % N–S for terrain-following designs) |
| Wind | Designed for full load | Designed for full load | Relies on stow strategy in storms |
| Best for | Hills, rock, cyclones, remote sites, tight capex | Mid latitudes with labour on site | Flat land, high direct sun, good energy price |
2. The tracker gain depends on direct sun, not latitude alone
A tracker earns its extra energy by pointing modules at the sun in the morning and afternoon. That only pays when most of the light arrives as direct beam. In NREL’s comparison, the southwestern United States sat at the top of the 12–25 % range and the cloudy Pacific Northwest and Atlantic coast at the bottom. Humid tropical sites with frequent cloud and high diffuse light therefore see smaller gains than dry, sunny ones at the same latitude.
The practical rule: do not take a percentage from a brochure. Run your yield model twice, once fixed at the optimum tilt and once with single-axis tracking and backtracking, using a typical meteorological year for the site. NREL’s free PVWatts calculator is enough for a first comparison; use PVsyst or similar for the final design.
3. Where fixed-tilt still wins
Berkeley Lab notes that new US fixed-tilt plants are now built mainly on “particularly challenging sites”, for example because of terrain or wind loading. The same logic applies elsewhere:
- Slopes beyond tracker limits. Fixed structures with posts of different lengths can follow much steeper ground. Our fixed ground-mount systems accept up to 30° north–south and 20° east–west. See our hillside design checklist.
- Typhoon and cyclone zones. A tracker survives storms by stowing; if power, controls or communications fail during an event, the rows are exposed. Fixed structures are simply designed for the full load.
- Remote operation. Motors and controllers need spare parts and trained technicians. Where a failed drive could wait weeks for a part, the yield advantage shrinks.
- Expensive groundwork. Grading and piling to tracker tolerances on uneven ground can cost more than the extra energy is worth.
4. Seasonally adjustable tilt: the middle option
Adjustable structures let a crew change the tilt two to four times a year: steeper in winter, flatter in summer. The gain over fixed-tilt is smaller than a tracker’s and grows with latitude, because the sun’s noon height changes more through the year. It suits sites with available labour where trackers are ruled out by slope, wind or maintenance. Model it like a tracker: run the yield both ways rather than relying on a rule of thumb. More on our adjustable-tilt structures.
5. Does the tracker pay back? A simple test
Before a detailed financial model, check the order of magnitude:
| Step | Example (illustration only) |
|---|---|
| Fixed-tilt specific yield from your model | 1,600 kWh per kWp per year |
| Tracker gain from the same model | +15 % = 240 kWh per kWp per year |
| Value of the extra energy | 240 kWh × your tariff or PPA price, every year, discounted over the project life |
| Compare with | Tracker capex premium per kWp + present value of extra O&M + extra groundwork |
If the value of the extra energy is not comfortably larger than the premium, the risk of moving parts is not worth taking. Note that the premium varies a lot by market and year: Berkeley Lab found that in the United States it rose in 2023, but in 2024 tracking projects actually cost less than fixed-tilt ones. Get current quotes for both before deciding.
6. Site checklist: questions to answer first
| Question | Points to a tracker if… | Points to fixed if… |
|---|---|---|
| Direct-beam share of sunlight | High (dry climate) | Low (humid, frequent cloud) |
| Slope and undulation (from survey) | Under about 15 % N–S | Steeper, or broken terrain |
| Design wind speed, cyclone exposure | Moderate, reliable stow possible | Cyclone or typhoon zone |
| Ground | Uniform soil, easy piling | Rock, boulders, mixed ground |
| O&M capacity | Technicians and parts nearby | Remote, long supply chains |
| Energy value | High tariff or PPA price | Low price, capex-limited |
FAQ
How much more energy does a single-axis tracker produce?
NREL found 12–25 % more than a fixed system at 25° tilt across 50 US cities, with the highest gains in dry, sunny climates. Your site’s figure comes from a yield model with local weather data, not from a general percentage.
What slope can a tracker handle?
Terrain-following single-axis trackers are published at around 15 % north–south (about 8.5°). Straight-row designs tolerate steeper uniform slopes but still need grading where the ground undulates. Beyond that, fixed structures are usually the practical choice.
Are trackers suitable for typhoon or cyclone areas?
They can be, if the design wind speed, stow logic and backup power are engineered for the site. Many owners in these zones still choose fixed-tilt because it does not depend on a control system working during the storm.
Is seasonally adjustable tilt worth it?
Where labour is available and trackers are ruled out, often yes. The gain is smaller than a tracker’s and larger at higher latitudes; model it before committing.
How we help
We supply fixed ground-mount, adjustable-tilt and single-axis tracker structures, so our recommendation follows your site rather than our stock. Send us the layout, survey, module data and design loads, and we will propose a structure and explain the trade-offs.
Sources: Lawrence Berkeley National Laboratory, Utility-Scale Solar, 2024 Edition and 2025 Data Update; Drury, Lopez, Denholm and Margolis, “Relative performance of tracking versus fixed tilt photovoltaic systems in the USA”, NREL / Progress in Photovoltaics; NREL, Model and Validation of Single-Axis Tracking with Bifacial PV (2019); manufacturers’ published slope data for terrain-following trackers (Nextracker NX Horizon-XTR, Array OmniTrack). Related: galvanizing specification, all mounting systems.