Production is physics, revenue is a contract, and the spread between them is the credit. Solar underwriting is offtake analysis wearing an energy model.
A solar project’s revenue is irradiance times capacity times an offtake price — and each term gets its own scrutiny. The production estimate is tested against the resource data and the system design’s realistic performance ratio, with degradation scheduled rather than ignored. The offtake structure then decides the credit: a contracted power purchase agreement with a rated counterparty is financeable revenue; merchant exposure is a commodity bet the coverage analysis must price, with EIA market data anchoring the merchant tail.
Interconnection is the schedule risk that strands more projects than weather: queue position, upgrade-cost allocation, and the utility’s timeline belong in the conditions precedent, not the appendix. The incentive stack — tax credits, depreciation, state programs, REAP support for rural projects through USDA Rural Development — requires sources-and-uses reconciliation with timing, and the coverage case must work on contracted revenue with the uncommitted layers stripped.
Wert-Berater’s clean-energy practice spans utility-scale and behind-the-meter solar, with production-to-coverage modeling, counterparty analysis on the offtake, and the land-control and decommissioning questions rural projects raise treated as the lender conditions they are.
Energy projects invert the demand question — the accepted methodology is probabilistic resource assessment paired with offtake analysis, because production is supply-side physics and “demand” is the contracted willingness to buy it. The resource assessment is defined by exceedance probabilities: P50 is the annual production with a 50 percent probability of being met or exceeded; P90 the production met or exceeded nine years in ten. Purpose: to size equity returns on expectation (P50) while sizing debt on the conservative case (P90), since the lender’s coverage must survive the poor resource years.
The mathematics: annual energy = capacity (kW) × 8,760 hours × net capacity factor, where the net factor applies itemized losses — soiling, wake or shading, availability, degradation at a stated annual rate — to the gross resource; and P90 ≈ P50 × (1 − 1.282σ) under a normal interannual distribution with resource variability σ. Revenue then follows the offtake stack: contracted revenue = P90 energy × PPA price, with merchant tail volumes priced from market data and stressed separately. Coverage is reported at P90-contracted as the lender’s case. The rationale: exceedance statistics replace a single optimistic number with a stated probability the committee can underwrite to — the discipline that distinguishes project finance from project hope.
Solar files flag at the seams between promise and contract. Production estimates at P50 presented as expectation with no P90 case for the lender whose debt lives in the difference. Offtake described as “in negotiation” carrying a pro forma priced as if executed. Interconnection treated as paperwork — queue position unverified, network-upgrade allocation unestimated — when it is the schedule’s controlling risk. The incentive stack flags constantly: coverage that only works with every tax benefit monetized on schedule, by a sponsor without the tax capacity to monetize them. And land control assembled as options about to expire into a development timeline that outruns them.
Mitigation in energy is sequencing discipline. We model coverage at P90 production on contracted revenue with uncommitted incentive layers stripped — the case the lender actually owns — and then show the upside cases above it; sponsors learn quickly that a project bankable at P90-contracted closes faster than one defended at P50-everything. Interconnection and offtake convert into enumerated conditions precedent with their documents named. Where the tax-equity gap is the weakness, the capital-stack conversation happens early — partnership structures, transferability, or a smaller phase the sponsor’s own capacity carries. The determination that results is conditional and useful: feasible upon executed offtake and interconnection agreement, with the margin at each milestone stated.
Contract before you model: every percentage point of revenue under executed offtake is worth more than ten points of projected merchant upside. Order the independent resource assessment early and let P90 discipline the design. Chase interconnection from day one — queue position is the asset. Build the incentive stack conservatively and document the monetization path for every layer you count. Secure land control with terms that survive the development timeline. And size phase one to the offtake you hold, not the capacity the parcel permits — the expansion case is stronger written as upside than as assumption.
The sector’s underwriting environment is defined by the interconnection bottleneck — queue reform is underway but timelines remain the binding constraint, and projects with positions are worth more than projects with land. Incentive transferability has broadened the monetization market, easing the tax-equity gap for mid-size sponsors, while policy-revision risk keeps stripped-incentive stress cases mandatory. Equipment costs have resumed their long decline after the supply-chain spike, improving buildable economics, and storage pairing has moved from exotic to expected in capacity-constrained markets — hybrid revenue modeling is becoming standard scope rather than special request.
Engagements are typically initiated by the borrower, with lender or CDC confirmation obtained before work begins — institutions apply differing rules, so sponsors should confirm the required path with their lending contact — and are delivered in 10 to 15 business days from complete project data, and built to the program framework that governs the credit — SBA SOP 50 10 8 coverage minimums of 1.15x operating and 1.00x global, the 37-factor structure of USDA RD Instruction 5001, or the 1.20x convention of conventional credit policy — with a ten-year pro forma, sensitivity at ±5/10/15 percent, rate stress to +3.0 percent, and Monte Carlo analysis as standard equipment.
President, Wert-Berater, Inc. — independent feasibility study consultants since 1998. More than 4,000 feasibility studies completed across all 50 states and internationally, evaluating $40.2 billion in project value for SBA, USDA, EB-5, conventional, and institutional financing decisions. Fiduciary duty runs to the lender and agency in every engagement.
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Schedule a ConversationIndependent feasibility studies since 1998 — 4,000+ engagements, $40.2 billion in evaluated project value. Standard delivery in 10 to 15 business days. Fiduciary duty to the lender and agency.