The Planning Problem

Without accurate build timelines, capacity commitments arrive too late, procurement cycles slip, and competitive windows close. For years, planners automatically penalized large-footprint projects with extended timelines — an assumption baked into financial models, supply agreements, and grid interconnection queues.

That assumption is no longer reliable. The 2025 dataset reveals a modest slowdown in solar construction, driven by tariff pressures on imported panels and a federal permitting environment that has become less accommodating of new solar facilities. Unlike the data center construction market — where Vulcan's analysis shows accelerating build activity — utility-scale solar is experiencing measurable friction.

The consequence: planners relying on 2023–2024 baseline timelines will systematically underestimate how long it takes projects currently breaking ground to reach commercial operation.

Project Spotlights: The Fastest and the Slowest

The 2025 dataset contains striking variation — not just across regions, but within the same state. Three projects define the extremes.

Fastest Overall: Hornet Solar Texas — 600 MW (Vesper Energy Development)

Hornet Solar Texas is the productivity standout of 2025. Land clearing began January 13, 2024. The first structure appeared 75 days later. Construction wrapped 344 days after that — an elapsed time of roughly 14 months from bare ground to completion on April 1, 2025.

At 0.57 days per MW, this is top-tier execution for a project of this scale. Post-completion capacity factors have remained solid, reflecting quality construction rather than a rushed finish.

Fastest Days/MW: Hornshadow Solar — 100 MW (Hornshadow Solar LLC, Utah)

The days-per-MW award goes to the 100 MW Hornshadow facility in Utah. Land was cleared April 23, 2024. But it sat idle: 252 days passed before the first structure appeared. Once active, however, the crew delivered an extraordinary 49-day sprint to completion — an almost unprecedented pace for a project this size.

The contrast between Hornshadow's slow mobilization and explosive finish, versus Hornet Solar's steady throughput, illustrates why land-clearing-to-first-structure variance is one of the least predictable variables in solar scheduling.

Slowest: Stoneridge Solar — 100 MW (RWE Clean Energy, Texas)

At the other end of the spectrum, Stoneridge Solar in Texas cleared land July 25, 2023, saw its first structure 221 days later, then took another 588 days to complete — a total of 5.88 days per MW.

Critically, Hornet Solar and Stoneridge are both in Texas. There is no meaningful regional advantage; both experienced the same grid and permitting environment. This strongly suggests that construction speed is determined primarily by contractor capability, supply chain access, and project management — not location.

* Days/MW calculated from first-structure date only; total elapsed time was much longer due to 252-day pre-mobilization delay.

Introducing the Weekly Progress Indicator

To better explain construction variance, Vulcan is launching a new metric for every active project in its dataset: the Weekly Progress Indicator (WPI).

WPI assigns a score each week:

• 0 — No observable progress

• 1 — Limited progress (site work, staging, minor activity)

• 2 — Significant progress (structural installation, electrical work, panel mounting)

This metric — the first of its kind focused on satellite-derived construction visibility — allows Vulcan to chart week-by-week momentum and derive a running percentage-completion estimate for any active project.

Projects with more high-intensity weeks (score 2) require fewer total weeks to complete. WPI also enables percentage-completion estimation, allowing Vulcan clients to track projected online dates in real time.

Key Finding: Administration and Policy Impact

The policy environment in 2025 created a split dynamic in solar construction. Two trends are running simultaneously — and pulling in opposite directions.

• Land clearing to first structure has gotten faster. Developers are mobilizing construction crews more quickly once a project breaks ground, likely because of the urgency created by IRA tax credit uncertainty.

• First structure to completion has widened by approximately 60 days compared to 2024. Panel procurement delays — driven by tariffs on solar equipment, including Chinese-manufactured modules — are slowing the structural phase.

Net effect: projects that do start construction are completing in roughly two months more than the equivalent 2024 project would have.

The rush to reach grandfathering eligibility before July 4, 2026, is likely compressing early-stage activity. This explains the faster land clearing observed in early 2025 - developers are starting construction on record, even if panel delivery isn't ready.

Probabilistic Build Profiling

The central objective of this research is to replace static estimates with a probability distribution. By analyzing the full distribution of first-structure-to-online durations across 125 projects, Vulcan has established three reference points for any project in its dataset:

• Earliest online date - based on top-quartile days/MW performance

• Median online date - the most likely scenario given current project characteristics

• Latest online date - based on bottom-quartile performance and current procurement delays

The methodology works in two stages. First, a land-clearing-to-first-structure equation is applied (this is where the largest variance exists, as Hornshadow vs. Hornet Solar demonstrates). Second, once a first structure is confirmed via satellite, a Days/MW factor is applied to generate the three reference dates.

This approach replaces one-number forecasts with a decision-ready range - exactly what procurement teams and grid operators need to plan interconnection queues and PPA delivery commitments.

What This Means for Your Planning

Solar still represents the largest share of US new capacity additions in the queue. Understanding the construction environment matters more than ever.

Projects In-Construction: Expect Delays

First-structure-to-completion timelines have stretched by approximately 60 days compared to 2024. Procurement teams sourcing panels under tariff pressure should add buffer to interconnection commitments.

2026 Pipeline: Severe Delay & Cancellations

When 2026 pipeline announcements first emerged, over 470 projects totaling over 36 GW claimed target online dates in 2026. Based on current construction data, the realistic 2026 figure is approximately 200 projects at around 21 GW along with over 15 GW that were delayed from previous years. 88 projects have been delayed totaling nearly 9 GW. 19 projects cancelled totaling 3 GW.

Grandfathering Rush Creates a False Signal

The urgency around the July 4, 2026, beginning-of-construction deadline means some projects will initiate site clearing to establish a construction start date — without being ready to build. This may inflate 'under construction' counts without translating to near-term online dates.

Dataset & Methodology

The forecasting method underlying the earliest, median, and latest online dates was recalibrated using the 125 solar projects from the 2025 cohort reviewed in this report, with an additional 142 completed projects from 2024 incorporated to strengthen the sample.

Forecasts are generated in two phases. The first phase covers land clearing to the first structure observed and is treated as independent of project capacity — historical durations show no meaningful relationship to project size, so the same range applies whether the project is 50 MW or 500 MW. The second phase runs from first structure to completion. Here, duration scales with project capacity, so the forecast applies a Days-per-MW factor that varies by capacity band. Larger projects benefit from clear economies of scale, with median Days-per-MW for projects in the under-100 MW band running roughly 2.5x that of projects in the 250 MW and larger band.

Within each phase, three reference points are drawn from the historical distribution to produce earliest, median, and latest online dates. The earliest bound is set at a fast-case threshold within each phase independently. Because the combined forecast requires both phases to clear that threshold simultaneously, the total earliest functions as a practical floor on construction timeline — projects that match it represent top-tier execution across both pre-construction mobilization and active build phases. Before first structure is observed, both phases contribute to the forecast. Once first structure is confirmed via satellite, the forecast narrows to the second phase alone, anchored to the observed first-structure date — meaningfully tightening the projected window.

The V2 forecast in Vulcan for power generation is based on multiple inputs (technology delays, EIA online dates, etc.), including the earliest and latest online metrics developed above. With the noted updates, we are shifting solar build projections earlier, aligning with the grandfathering window for renewable projects under the One Big Beautiful Bill.