Engineering Smarter, Not Harder: 3 Utility-Scale Solar Design Trends

Written by Arun Ramadass, VP of Operations, and Brett Beattie, Director of Civil Engineering

As engineers, we’ve seen many trends come and go in utility-scale solar. Some solve real problems; others just shift the challenges somewhere else.

Right now, the industry is focused on how to make projects work within tighter margins and on increasingly complex sites. Our goal is to use sound engineering judgment to balance stakeholders’ three main objectives:

• Cost

• Constructibility

• Long-term performance

At Castillo Engineering, we work on dozens of projects each year across the country. Many of them start with the same question: how can we deliver a reliable system while keeping costs predictable?

The answer depends on the ground under your feet (literally and figuratively!)

Trend 1: Terrain-Following Trackers

Terrain-following trackers allow for more uneven terrain between posts, so they’re often marketed as a way to reduce grading and cut civil costs. On some sites, they do present concrete savings, including:

• Fewer machines needed on site

• Shorter earthwork timelines

• Lower earthwork costs

• Less dirt moved, creating less environmental disruption

• Lowered risk of grading-related erosion

But terrain-following trackers aren’t a silver bullet, or automatically the best fit for all sites with uneven terrain. When you examine the details, the savings aren’t always as clear as they seem.

In many cases, terrain-following systems add complexity to construction, requiring:

• More labor hours (and costs) in the field

• Greater precision during installation

• More risk of equipment failure during commissioning

For projects that already have heavy equipment onsite for roads, drainage, or trenching, the cost of moving extra dirt can be negligible compared to the added labor burden of complex tracker installation. Sometimes, a small amount of additional grading can simplify installation, improve mechanical tolerances, and even lower long-term O&M costs.

On other sites, especially those with environmentally sensitive or uneven land, terrain-following technology may indeed be the best fit. That’s why our engineering team always calculates both sides of the equation for each project, comparing projected pile quantities and racking costs in addition to earthwork expenses. The best outcome comes from a deep understanding of each individual site and its needs.

Trend 2: Module Flexibility

Another major trend is how we design around unpredictable module supply costs and chains. Since the ITC credits are sunsetting, developers are under growing pressure to safe-harbor materials and secure tax credit eligibility, even when the timing of module deliveries is uncertain.

That uncertainty has encouraged engineers to design modules that can adapt to multiple racking classes and suppliers. Like terrain-following trackers, this is a practical idea in theory, and can work for many sites – but not all.

Module flexibility has a cost, often requiring:

• Oversized cables

• Adjusted tracker lengths

• Increased structural load allowances

These factors can significantly affect project budgets.

Again, the key is to be deliberate about where flexibility truly adds value. For projects a year or more from construction, designing for module variability can protect schedules and financial performance. For shovel-ready sites, however, over-designing for every potential scenario adds cost without reducing real risk.

So we include those factors when deciding whether to design a project for module flexibility. Our proprietary software, Design IQ, enables us to quickly analyze multiple design scenarios, account for the client’s budget and project risk, and identify the most flexible, cost-effective design for each project.

Trend 3: (Over-) Designing for the Worst-Case Scenario

The first two trends indicate one of the best opportunities to improve utility-scale project economics: analyzing how civil, structural, and electrical design interact per project. Grading, racking, module choice, and electrical layouts are often optimized in isolation, when they actually belong to the same cost and risk curve.

Every site faces a balance between lowering risk and controlling upfront cost. When uncertainty around module supply or equipment timing becomes a factor, many teams default to designing for the absolute worst-case scenario.

That might include laying out a site for the least efficient module, but designing the electrical system for the largest possible current. Or it could be ordering heavier gauge wire and adding extra tracker rows to accommodate future module swaps.

The worst-case design approach can reduce risk, but it often adds unnecessary cost. The right question is not whether to design for project flexibility, but how much flexibility is worth paying for. In some cases, the additional materials, labor, and procurement costs outweigh the risk they’re meant to hedge against.

Again, there are situations where strategic overdesign makes sense! For instance, looming tax credit deadlines or safe-harbor opportunities can make it worth building the balance of system before finalizing module choice. The tax credit value can offset the added expense required for module flexibility. In this case, spending more upfront protects the project’s financial foundation.

The key is to make that decision intentionally, not by default.

The Castillo Approach: A Value-Engineering Mindset

When our team begins designing a project, we model both extremes for each factor: for instance, one version with minimal grading and many terrain-following trackers, and another that assumes a completely leveled site. Then we integrate how civil, construction, and long-term performance prices interact in these different scenarios. Comparing the extreme approaches reveals where the most cost-effective approach falls between them.

Smart design finds the middle ground. It’s based on accurate modeling of cost, risk, and schedule, and adapts as conditions change rather than locking in unnecessary expense from the start. That requires understanding what happens downstream when slope tolerances, trench routes, or tracker selections change.

It also demands early engagement. The earlier an engineering team has access to site data, interconnection requirements, and preferred racking systems, the more opportunities there are to identify cost savings through smarter coordination.

Utility-scale solar design trends may shift quickly, but the fundamentals remain the same: strong coordination, data-driven decision-making, and early alignment among all project partners. Whether managing terrain variation, planning for uncertain module supply, or balancing grading and steel, the most effective solutions come from seeing the project as a whole system rather than a collection of separate scopes.

Engineering is about connecting those pieces: the cost, the schedule, and the long-term reliability of what we build. Smarter design doesn’t mean doing more work; it means focusing on what delivers lasting value.